JP7097072B2 - Use of stress-stimulated luminescent materials, stress-stimulated luminescent materials, and stress-stimulated luminescent materials - Google Patents

Description

The present invention relates to a stress-stimulated luminescent material, a stress-stimulated luminescent material, and the use of a stress-stimulated luminescent material.

Conventionally, stress-stimulated luminescent materials have been known as materials that emit luminescence correlated with their energy by external mechanical stimuli, such as sensors, non-destructive inspection, stress distribution visualization, stress sensing, and structural anomalies. -It is expected to have various uses such as danger detection.

Therefore, so far, stress-stimulated luminescent materials capable of emitting light according to stress at various wavelengths from the ultraviolet region wavelength to the near-infrared region wavelength have been developed.

Among them, stress-stimulated luminescent materials using a piezoelectric material as a base material have been studied in various ways because they have the advantages of being able to perform various electronic control functions and being capable of multiple conversion of electricity, force, and light.

However, the stress-stimulated luminescent materials examined so far using a piezoelectric material as a base material have weak piezoelectricity for those having a relatively high stress-stimulated luminescence intensity, and those using a strong piezoelectric material as a base material have weak piezoelectricity. The stress luminescence intensity tends to be weak.

Therefore, the present inventors have conducted diligent research and have proposed in the past an attempt to improve the emission intensity as a mixed phase in which a plurality of crystal structures are mixed (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2010-7437

However, the conventional stress-stimulated luminescent material is composed of a mixed phase, and a single-phase stress-stimulated luminescent material, which is a piezoelectric material, has not been known so far.

Further, regarding the abnormality / danger detection of structures, the development of a stress-stimulated luminescent material capable of detecting stress concentration with high sensitivity in order to predict the danger level of defects is expected. However, the threshold for detecting strain was high, and it was difficult to emit light with a small strain (0-100 μst) such as 1 / 10,000 or less.

The present invention has been made in view of such circumstances, and provides a single-phase stress-stimulated luminescent material using a piezoelectric body as a base material, which can emit light with high sensitivity even with a minute force.

The present invention also provides a stress-stimulated luminescent material in which a stress-stimulated luminescent material is dispersed in a predetermined matrix material, the use of the stress-stimulated luminescent material, and a method for manufacturing the stress-stimulated luminescent material.

In order to solve the above-mentioned conventional problems, in the stress-stimulated luminescent material according to the present invention, (1) a part of Li constituting a crystal of LiNbO ₃ is selected from Pr ³⁺ , Er ³⁺ , and Eu ³⁺ . It has a non-stoichiometric composition represented by the general formula Li _x NbO ₃ : My substituted with at least one metal ion M, x> 1- _y , and 0.001 ≤ y ≤ 0.1 . , 0.99 ≤ x ≤ 2.4 .

Further, the stress-stimulated luminescent material according to the present invention is characterized in that ( 2 ) the stress-stimulated luminescent material described in (1 ) above is dispersed in a predetermined matrix material.

Further, the present invention is characterized by ( 3 ) the use of the stress-stimulated luminescent material according to (1 ) above for detecting a force of 1000 pN or less by luminescence.

Further, the present invention is characterized by ( 4 ) the use of the stress-stimulated luminescent material according to (1 ) above for detecting minute strains of 100 μst or less by luminescence.

Further, in the method for producing a stress-emitting material according to the present invention, a niobium compound, a lithium compound, and a compound of at least one metal selected from praseodymium, erbium, and europium are mixed and fired to obtain LiNbO ₃ . _Tabled by the general formula Li _x NbO ₃ : My, which is a parent material and some of the Lis constituting the crystal are substituted with at least one metal ion M selected from Pr ³⁺ , Er ³⁺ , and Eu ³⁺ . It is a method for producing a stress-emitting material having a non-chemical composition, x> 1-y, and 0.001 ≤ y ≤ 0.1 , in which the molar ratio of niobium atom to lithium atom is 1: 1. It is characterized by being 0.99 to 2.4 .

According to the stress-stimulated luminescent material according to the present invention, a part of Li constituting the crystal of LiNbO ₃ is replaced with at least one metal ion selected from rare earth metal ions and transition metal ions. It is possible to provide a single-phase mechanoluminescent material using a piezoelectric material as a base material, which can emit light with high sensitivity even with a strong force.

In addition, the general formula Li _x NbO ₃ : My ₍ where M is at least one metal ion selected from rare earth metal ions and transition metal ions that replace some of the Lis constituting the crystals of LiNbO ₃ ). If it has a non-chemical quantitative composition represented by, x = 1-y, and 0.0001 ≤ y ≤ 0.2, it is possible to generate light emission more steadily in response to stress.

In addition, the general formula Li _x NbO ₃ : My ₍ where M is at least one metal ion selected from rare earth metal ions and transition metal ions that replace some of the Lis constituting the crystals of LiNbO ₃ ). If it has a non-chemical quantitative composition represented by, x> 1-y, and 0.0001 ≤ y ≤ 0.2, the emission intensity can be further improved.

Further, if 0.8 <x ≦ 3.0, the emission intensity can be improved more steadily.

Further, if the metal ion is Pr ³⁺ , it is possible to generate light emission more steadily according to the stress.

Further, according to the stress-stimulated luminescent material according to the present invention, since these stress-stimulated luminescent materials are dispersed in a predetermined matrix material, it is possible to provide a stress-stimulated luminescent material that emits light when subjected to stress.

Further, if the above-mentioned stress-stimulated luminescent material is used to detect a force of 1000 pN or less by light emission, a minute force of 1000 pN or less can be detected by light emission.

Further, if the above-mentioned stress-stimulated luminescent material is used to detect minute strains of 100 μst or less by light emission, minute strains of 100 μst or less can be detected by light emission.

Further, according to the method for producing a stress-emitting material according to the present invention, LiNbO ₃ which is a mixture of a niobium compound, a lithium compound, and a compound of at least one metal selected from a rare earth metal and a transition metal and fired is used as a base. It is a method of manufacturing a stress-emitting material as a material, and since the molar ratio of niobium atom to lithium atom is set to 1: 0.8 to 3.0, it is possible to emit light with high sensitivity even for minute stress, piezoelectric. It is possible to produce a single-phase stress-emitting material using a body as a base material.

It is explanatory drawing which shows the identification result of the crystal phase by the X-ray diffractometer. It is explanatory drawing which shows the fluorescence spectroscopic spectrum measurement result, the mechanoluminescence spectrum (a), and the relationship (b) between a Pr doping amount and fluorescence intensity. It is explanatory drawing which shows the stress mechanoluminescence curve (a) obtained by subjecting a stress-stimulated luminescent material to a stress-stimulated luminescence evaluation system, and the relationship (b) between a Pr-doped amount and stress-stimulated luminescence intensity. It is explanatory drawing which shows the result of the crystal phase and the calculated lattice constant by the X-ray diffractometer. It is explanatory drawing which shows the stress mechanoluminescence curve obtained by subjecting a stress mechanoluminescence body to a stress mechanoluminescence evaluation system. It is explanatory drawing which showed the change of the light emission intensity with respect to the strain. It is explanatory drawing (a) which showed the time-dependent change of a load and luminescence intensity, and is an explanatory diagram (b) which showed the comparison between the stress luminescence intensity distribution and the quantitative analysis result of a stress distribution. It is explanatory drawing which shows the identification result of the crystal phase by the X-ray diffractometer. It is explanatory drawing which shows the stress mechanoluminescence curve obtained by subjecting a stress mechanoluminescence body to a stress mechanoluminescence evaluation system. It is explanatory drawing which shows the stress luminescence intensity at the time of doping with Eu ³⁺ , Er ³⁺ , Nd ³⁺ .

The present invention provides a stress-stimulated luminescent material in which a part of Li constituting a crystal of LiNbO ₃ is substituted with at least one metal ion selected from a rare earth metal ion and a transition metal ion.

As mentioned above, the stress-stimulated luminescent material is a material that exhibits luminescence correlated with its energy by mechanical stimulation, and is expected to be applied to various fields.

The present inventor has developed various stress-stimulated luminescent materials, and has also conducted research on stress-stimulated luminescent materials using a piezoelectric material as a base material. However, stress-stimulated luminescence can be confirmed with famous piezoelectric materials such as PZT. However, Ba _1-x Ca _x TiO ₃ : Pr ³⁺ emitted light in response to stress, but this was due to the combined action of the piezoelectric phase and electroluminescence phase, and stress emission in a single phase could not be realized. rice field. That is, the results so far have shown that those using a typical piezoelectric material as the base material do not exhibit good mechanoluminescence.

On the other hand, LiNbO ₃ is a ferroelectric substance with a high Curie temperature, and has been attracting attention for a long time due to its piezoelectric characteristics, electro-optical characteristics, and nonlinear optical characteristics, and is currently widely used as an excellent electrical / optical material. ..

The present inventors have discovered for the first time that the function as a stress-stimulated luminescent material is exhibited by doping this LiNbO ₃ with Pr ³⁺ through diligent research, and have completed the present invention.

That is, it can be said that the present invention relates to a stress-stimulated luminescent material whose base material is LiNbO ₃ doped with Pr ³⁺ , which is the first material exhibiting both high piezoelectric properties and stress-stimulated luminescence properties.

Further, the stress-stimulated luminescent material according to the present embodiment is characterized by being a single-phase material, although it is a base material having piezoelectricity. Here, the single phase means that the process from excitation to luminescence is completed in a single type of crystal phase regardless of other crystal phases, and the generated stress-stimulated luminescent material does not contain an impurity phase. It does not necessarily mean that. That is, the crystalline phase characteristic of the stress-stimulated luminescent material according to the present embodiment, that is, a part of Li constituting the crystal of LiNbO ₃ , is composed of at least one metal ion selected from rare earth metal ions and transition metal ions. If the substituted stress-luminescent phase is included, it will have stress-stimulated luminescent properties regardless of the presence or absence of other impurity phases.

In the stress-emitting material according to the present embodiment, the rare earth metal ions are, for example, Sc (scandium), Y (yttrium), La (lantern), Ce (cerium), Pr (placeodim), Nd (neodim), Pm (promethium). , Sm (samarium), Eu (europium), Gd (gadrinium), Tb (terbium), Dy (dysprosium), Ho (holmium), Er (erbium), Tm (yttrium), Yb (yttrium), Lu (lutettrium) Can be understood as an ion of.

Further, the transition metal ion can be understood as an ion of the transition metal existing between the group 3 element and the group 11 element.

In the stress-stimulated luminescent material according to the present embodiment, the metal ion used for substituting a part of Li constituting the crystal of LiNbO ₃ is particularly limited as long as it is the above-mentioned rare earth metal ion or transition metal ion. It's not a thing.

Further, according to such a stress-stimulated luminescent material, it is possible to obtain a single-phase stress-stimulated luminescent material using a piezoelectric body as a base material, which can emit light with high sensitivity even for a minute stress.

The stress-stimulated luminescent material according to this embodiment is derived from the general formula Li _x NbO ₃ : My ₍ where M is a rare earth metal ion or a transition metal ion that replaces a part of Li constituting the crystal of LiNbO ₃ ). It has a non-chemical quantitative composition represented by at least one selected metal ion.), X = 1-y, and 0.0001 ≦ y ≦ 0.2.

Here, if y is less than 0.0001, the emission intensity is significantly lowered, which is not preferable. When y exceeds 0.2, the proportion of impurities increases and the proportion of mechanoluminescent LiNbO ₃ crystal phase decreases, which is not preferable because the stress-stimulated luminescence intensity decreases. By setting 0.0001 ≤ y ≤ 0.2, it is possible to generate light emission more steadily according to the stress.

Further, the stress-stimulated luminescent material according to the present embodiment has a non-stoichiometric composition represented by the general formula Li _x NbO ₃ : My, x> 1- _y , and 0.0001 ≤ y ≤ 0.2. It may be.

This will be explained later with reference to the drawings, but it is one of the notable configurations found by the present inventors, and it contains lithium and metal ions rather than lithium required for constructing the crystal structure of LiNbO ₃ . By increasing the sum of the above and allowing an excess amount to exist, the emission intensity can be further improved and the luminous efficiency can be increased.

Further, x at this time may be 0.8 <x ≦ 3.0. With such a configuration, it is possible to obtain a stress-stimulated luminescent material that emits light with extremely high efficiency.

Further, the metal ion may be Pr ³⁺ . With such a configuration, it is possible to generate light emission according to stress more steadily and with high efficiency.

Since the stress-stimulated luminescent material according to the present embodiment having such a configuration has extremely high stress responsiveness, it can be used, for example, to detect a force of 1000 pN or less by luminescence.

Further, for example, it can be used to detect minute strain of 100 μst or less by light emission.

Further, the stress-stimulated luminescent material according to the present embodiment described above may be dispersed in a predetermined matrix material to form a stress-stimulated luminescent material. For example, a curable resin is used as a matrix material, and a powdered mechanoluminescent material is dispersed in the resin before curing and cured to facilitate a stress-stimulated luminescent material having a desired shape that emits light by applying stress. Can be formed into. As the matrix material, at least an excitation light for exciting the stress-stimulated luminescent material mixed in the matrix material and a material capable of transmitting fluorescence emitted from the stress-stimulated luminescent material are used.

Further, the stress-stimulated luminescent material is not limited to a solid, and may be a liquid material having fluidity. Specifically, a paint or the like mixed with the stress-stimulated luminescent material according to the present embodiment is also included in the concept of the stress-stimulated luminescent material.

Further, in the method for producing a stress-emitting material according to the present embodiment, LiNbO ₃ is used as a base material in which a niobium compound, a lithium compound, and a compound of at least one metal selected from a rare earth metal and a transition metal are mixed and fired. The method for producing a stress-emitting material is characterized in that the molar ratio of niobium atom to lithium atom is 1: 0.8 to 3.0.

Here, the niobium compound is not particularly limited as long as it is a compound capable of constructing a crystal of LiNbO ₃ through a mixing or firing process, and may be, for example, Nb ₂ O ₅ , Nb Cl ₅ , Nb F ₅ , or the like. can.

Similarly, the lithium compound is not particularly limited as long as it is a compound capable of constructing a crystal of LiNbO ₃ , and may be, for example, Li ₂ CO ₃ , Li NO ₃ , Li Cl, or the like.

Further, the compound of at least one metal selected from rare earth metals and transition metals is not particularly limited, and oxides of the same metal and the like can be used. For example, when Pr is selected as the metal, Pr is selected. It can be Pr ₂ O ₃ , Pr Cl ₃ , Pr (NO ₃ ) ₃ , etc.

It should be noted that it is not always necessary to use a separate compound for each of the above-mentioned compounds, and such a compound can be used if there is a compound containing any two elements or the like.

Mixing of these compounds can be carried out according to a known synthesis method regardless of whether it is dry type or wet type. As an example, the solid phase synthesis method may be used.

Further, the method for producing a stress-stimulated luminescent material according to the present embodiment is characterized in that the molar ratio of niobium atom to lithium atom is 1: 0.8 to 3.0, and more specifically, 1: 0.95 to 2.4. Be done.

If the ratio of lithium atoms is less than 0.8 with respect to the ratio of niobium atoms 1, the luminous efficiency is significantly reduced, which is not preferable. Further, when the ratio of lithium atoms exceeds 3.0, the luminous efficiency is significantly reduced, which is not preferable. By setting the molar ratio of niobium atom to lithium atom to 1: 0.8 to 3.0, more preferably 1: 0.95 to 2.4, a stress-stimulated luminescent material that responds to stress with extremely high efficiency can be produced.

Hereinafter, the stress-stimulated luminescent material according to this embodiment will be further described with reference to the drawings.

[1. Preparation of stress-stimulated luminescent material]
The sample was prepared by the solid phase synthesis method. Using Nb ₂ O ₅ as a niobium compound, Li ₂ CO ₃ as a lithium compound, and Pr ₂ O ₃ as a compound of at least one metal selected from rare earth metals and transition metals, Li _x NbO ₃ : Pr ^{3 +} _y x After weighing so that and y had the desired composition, they were mixed and crushed in a niobium dairy pot. x was adjusted within the range of 0.8 <x ≤ 3.0, and y was adjusted within the range of 0.0001 ≤ y ≤ 0.2.

Then, these were calcined in an electric furnace to prepare a sample. At the time of firing, the reaction precursor powder was molded into pellets by a hydraulic machine and fired. The firing was performed in a muffle furnace, and the firing conditions were 1050 ° C for 8 hours in the atmosphere and the heating rate was 3 ° C / min. The calcined sample was pulverized in a mortar and subjected to various measurements as a powder of the stress-stimulated luminescent material according to the present embodiment.

[2. Examination of Li _x NbO ₃ : Pr ^{3 +} _y (x = 1, 0 ≤ y ≤ 0.1)]
Above [1. Preparation of stress-stimulated luminescent material], Li _x NbO ₃ : Pr ^{3 +} _y (x = 1, 0 ≤ y ≤ 0.1) was prepared. The crystal phase of the prepared sample was identified by a powder X-ray diffractometer. The results are shown in FIG.

As can be seen from FIG. 1, the formation of LiNbO ₃ was confirmed at any doping amount. Further, in the sample in which the Pr ³⁺ doping amount was less than 2 mol%, as shown in the chart of 0.5 mol% in FIG. 1, no remarkable peak derived from the impurity phase was confirmed. On the other hand, in the sample in which the Pr ³⁺ doping amount was 2 mol% to 10 mol%, as shown in the chart of 10 mol% in FIG. 1, a peak considered to be derived from the impurity phase was observed. In addition, in the sample with a low doping amount of 0 mol% to 0.5 mol%, some orientation was observed in the crystal phase.

Next, the fluorescence characteristics were evaluated by a fluorescence spectrophotometer. FIG. 2A shows the results of fluorescence spectroscopy measurement. Fluorescence could not be confirmed when Pr ^{3+, which is the center of emission, was not doped, and when Pr 3+ was} doped, an emission peak was observed near 620 nm, as shown in FIG. 2 (a). As shown in FIG. 2 (b), the fluorescence characteristic for the amount of Pr ³⁺ doping is about 160 [au] at the maximum when x = 1, y = 0.001 for Li _x NbO ₃ : Pr ³⁺ _y . Shown, about 120 [au] when x = 1, y = 0.005, about 150 [au] when x = 1, y = 0.01, about 100 [au] when x = 1, y = 0.02 to 0.05. ], When x = 1, y = 0.1, about 85 [au] was shown.

Next, the stress-stimulated luminescence characteristics were evaluated. The stress-stimulated luminescence characteristics were evaluated by a stress-stimulated luminescence evaluation system in which a cylindrical resin pellet (diameter: 2.5 cm, height: 1.5 cm) was prepared by mixing a fired sample and a resin to form a stress-stimulated luminescent material. The measuring method was to apply a vertical load to the resin pellets and measure the emission intensity at that time with a photon sensor. The results are shown in FIG.

FIG. 3A is a stress-stimulated luminescence curve of each sample. No emission was shown in the sample not doped with Pr ³⁺ . On the other hand, in the Pr ³⁺ -doped sample, stress luminescence was confirmed as the applied load increased. In addition, it was observed that the stress-stimulated luminescence intensity increased as the doping amount increased, and the sample prepared this time showed the highest stress-stimulated luminescence intensity at 5 mol%. In particular, in terms of fluorescence intensity, as shown in FIG. 2B, the fluorescence emission intensity of the 5 mol% added sample was lower than that of the 0.5 mol% added sample, whereas the stress luminescence intensity was 0.5 mol%. It is interesting to note that the results showed that the 5 mol% added sample had higher luminescence intensity than the added sample. In addition, for Li _x NbO ₃ : Pr ^{3 +} _y (x = 1, [y = 0.001, 0.005, 0.01, 0.02, 0.03, 0.05, 0.1]), the relationship between the Pr ³⁺ doping amount and the stress luminescence intensity was examined. As a result, it was confirmed that the stress luminescence intensity tended to increase according to the doping amount up to 5 mol% (y = 0.05), but the stress luminescence intensity decreased at 10 mol% (y = 0.1). ..

[3. Examination of Li _x NbO ₃ : Pr ^{3 +} _y (0.95 ≤ x ≤ 1.05, y = 0.01)]
The above-mentioned [1. Preparation of stress-stimulated luminescent material], Li _x NbO ₃ : Pr ^{3 +} _y (0.95 ≤ x ≤ 1.05, y = 0.01) was prepared. The crystal phase of the prepared sample was identified by a powder X-ray diffractometer. The results are shown in FIG.

As can be seen from FIG. 4 (a), for Li _x NbO ₃ : Pr ^{3 +} _y ([x = 0.95, 0.97, 0.99, 1.00], y = 0.01), the impurity phases other than Li NbO ₃ are in all cases. It was not confirmed, and it was confirmed that a single phase of LiNbO ₃ (PDF No.01-085-2456) was formed. For Li _x NbO ₃ : Pr ^{3 +} _y ([x = 1.03, 1.05], y = 0.01), a small amount of Li ₃ NbO ₄ crystal phase was confirmed as the impurity phase.

Next, based on the data obtained by X-ray analysis, Rietveld refinement was performed to examine the lattice constant. The result is shown in FIG. 4 (b).

In FIG. 4 (b), the horizontal axis shows the value of x of Li _x NbO ₃ : Pr ^{3 +} _y (0.95 ≦ x ≦ 1.05), the left vertical axis shows the lattice constant a, and the right vertical axis shows the axial ratio c / a. There is. As can be seen from FIG. 4 (b), the difference in crystal structure due to the difference in the value of x became clear.

Especially for the lattice constant a, the value of x shows a relatively high value exceeding 5.152 at 0.95 and 0.97, and the value of x maintains a relatively low value below 5.151 from 0.99 to 1.03, which is the stoichiometric ratio. However, when the value of x reached 1.05, it showed an increasing tendency again.

In the axial ratio c / a, the value of x showed a downward trend from 0.95 to 0.97, but it showed a sharp increase in the process from 0.97 to 0.99 and 1.00, and the value of x was 1.03 and 1.05. Although there were some fluctuations, there was a tendency to maintain relatively high prices.

Next, the stress-stimulated luminescence characteristics were evaluated. The previous [2. Similar to the study of Li _x NbO ₃ : Pr ^{3 +} _y (x = 1, 0 ≤ y ≤ 0.1)], the mechanoluminescent properties are a cylindrical resin pellet (diameter: 2.5 cm, high) made by mixing the calcined sample and the resin. (S: 1.5 cm) was prepared and used as a mechanoluminescent material, and evaluated by the mechanoluminescent evaluation system. The measuring method was to apply a vertical load to the resin pellets and measure the emission intensity at that time with a photon sensor. The results are shown in FIG.

FIG. 5A is a stress-stimulated luminescence curve for each sample with a load of 0 to 1000 N when the value of x is changed within the range of 0.95 ≤ x ≤ 1.00 for Li _x NbO ₃ : Pr ^{3 +} _0.01 . FIG. 5 (b) is a graph showing the luminescence intensity of each sample at a load of 1000 N when the value of x is changed within the range of 0.95 ≤ x ≤ 1.05 for Li _x NbO ₃ : Pr ^{3 +} _0.01 . Is.

As can be seen from FIG. 5A, light emission was confirmed in all cases where the value of x was within the range of 0.95 ≦ x ≦ 1.00. Further, as shown in FIG. 5 (b), in particular, when the value of x exceeds 0.97, the luminescence is remarkably enhanced, and even if the stoichiometric ratio exceeds x + y = 1.00 (x = 0.99), The tendency to increase the emission intensity was maintained, and the maximum value was confirmed at x = 1.00. In addition, by blending a larger amount of lithium than the stoichiometric ratio Li _x NbO ₃ : Pr ^{3 +} _y (x = 0.99, y = 0.01), it shows extremely remarkable responsiveness to stress. Was confirmed.

Further, considering the result of FIG. 4 (b) shown above, it is considered that this enhancement of the luminescence intensity is due to the difference in the crystal structure derived from the amount of lithium x, and the lattice constant a is less than 5.151. Moreover, it can be said that a stress-stimulated luminescent material containing Li _x NbO ₃ : Pr ^{3 +} _y having a crystal structure having an axial ratio c / a exceeding 2.6900 can be used as a stress-stimulated luminescent material having excellent stress responsiveness. ..

Next, for Li _1.00 NbO ₃ : Pr ^{3 +} _0.01 , the relationship between strain and emission intensity was examined. Specifically, a powder of Li _1.00 NbO ₃ : Pr ^{3 +} _0.01 having an average particle size of about 1 μm was dispersed in an epoxy resin, and a stress-stimulated luminescent sheet having a thickness of 50 μm was prepared by a spray method. By subjecting it to a tensile tester, the stress-stimulated luminescence characteristics generated during the tensile test were evaluated. The results are shown in FIG. FIG. 6 shows the results of five repeated tests on the emission intensity when a strain of 0 to 2000 μst was applied. As can be seen from FIG. 6, extremely strong mechanoluminescence was confirmed according to the strain of 0 to 2000 μst. In particular, as shown in a partially enlarged view, excellent linearity was shown even between 0 and 300 μst, and an emission intensity of about 1000 [au] was observed even between 0 and 100 μst. This is because the stress-stimulated luminescent material so far emits almost no light against a strain of 100 μst or less, or even if it emits light, it emits light with a light emission intensity of about 10 [au] or less. It turns out that there is.

That is, as can be seen from FIG. 6, the stress-stimulated luminescent material according to the present embodiment exhibits unprecedented ultra-high sensitivity, and when strain is repeatedly applied, ultra-high-sensitivity mechanoluminescence is repeated with good reproducibility. It was confirmed that it was shown. In particular, even within the range of small strain (0 to 300 μst, especially 0 to 100 μst), the stress-stimulated luminescence intensity of the LiNbO ₃ : Pr ³⁺ coating film increases linearly as the strain increases, and LiNbO ₃ : Pr. It was confirmed that it is possible to obtain mechanoluminescence with small strain and high sensitivity using ³⁺ . In particular, since the Young's modulus of the stress-stimulated luminescent sheet is about several Gpa, the force F applied to the fine particles of the stress-stimulated luminescent material having a diameter of 1 μm is
Considering that F = area × stress = μm × μm × Young's modulus × strain, the force F is a pN level force. Therefore, from the results of this experiment, the stress-stimulated luminescent material according to the present embodiment has a pN level force. Can be detected.

For Li _0.99 NbO ₃ : Pr ^{3 +} _0.01 , FIG. 7 (a) shows the change over time between stress and light emission, and FIG. 7 (b) shows the relationship between equivalent stress and linear proportionality.

From FIG. 7 (a), it can be seen that the stress-stimulated luminescence intensity increases with the load.

Further, from FIG. 7B, it can be seen that the results are in good agreement with the calculation results of the equivalent stress distribution and are useful for quantitative analysis.

[4. Examination of Li _x NbO ₃ : Pr ^{3 +} _y (1.00 ≤ x ≤ 2.4, y = 0.01)]
The above-mentioned [1. Preparation of stress-stimulated luminescent material], Li _x NbO ₃ : Pr ^{3 +} _y (1.00 ≤ x ≤ 2.4, y = 0.01) was prepared. The crystal phase of the prepared sample was identified by a powder X-ray diffractometer. The results are shown in FIG.

As shown in FIG. 8, when Li _x NbO ₃ : Pr ³⁺ _y (x = 1.0, y = 0.01), no impurity phase other than LiNbO ₃ was confirmed, but Li _x NbO ₃ : Pr ³⁺ . _{At y} ([x = 1.2, 1.4, 1.6, 1.8, 2.0, 2.2, 2.4], y = 0.01), it was confirmed that the crystal phase of Li ₃ NbO ₄ gradually increased as the proportion of Li increased. rice field.

Next, the stress-stimulated luminescence characteristics were evaluated. The previous [2. Similar to the study of Li _x NbO ₃ : Pr ^{3 +} _y (x = 1, 0 ≤ y ≤ 0.1)], the mechanoluminescent properties are a cylindrical resin pellet (diameter: 2.5 cm, high) made by mixing the calcined sample and the resin. (S: 1.5 cm) was prepared and used as a mechanoluminescent material, and evaluated by the mechanoluminescent evaluation system. The measuring method was to apply a vertical load to the resin pellets and measure the emission intensity at that time with a photon sensor. The results are shown in FIG.

Figures 9 (a) to 9 (e) show the load of 0 to 1000 N in each sample when the value of x is changed to 1.0, 1.2, 1.4, 1.6, 1.8, 2.4 for Li _x NbO ₃ : Pr ^{3 +} _0.01 . It is a graph which showed the time-dependent change of the stress luminescence up to.

As shown in FIG. 9, when a maximum load of 1000 N was applied in a triangular wave shape for two consecutive times, a maximum emission of 980 [a.u.] was confirmed at x = 1.0 at the first 1000 N load, and then x = 1.2. 7238 [a.u.] at x = 1.4, 7996 [a.u.] at x = 1.6, 9680 [a.u.] at x = 1.6, and 10481 [a.u.] at x = 1.8.

Moreover, when the lithium ratio was further increased and x = 2.4, a decrease in emission intensity was observed at 1929. However, even with such a luminescence intensity, it is a luminescence intensity that cannot be realized by a conventional stress-stimulated luminescent material using a piezoelectric body as a base material.

As shown in FIG. 8, in Li _x NbO ₃ : Pr ^{3 +} _y ([x = 1.2, 1.4, 1.6, 1.8, 2.0, 2.2, 2.4], y = 0.01), the Li ₃ NbO ₄ Although the crystal phase is generated as an impurity phase, this Li ₃ NbO ₄ crystal phase does not contribute to stress-stimulated luminescence, and Li _x NbO ₃ : Pr ^{3 +} _y ([x = 1.2, 1.4, 1.6, 1.8) , 2.0, 2.2, 2.4], y = 0.01) It has been clarified by the studies of the present inventors that the stress response is completed by the crystal alone.

Further, it should be noted that the stress-stimulated luminescent material according to the present embodiment can sufficiently emit light according to the stress even when it has an impurity phase. From this point as well, it can be seen that the impurity phase does not contribute to stress luminescence and does not inhibit stress luminescence to the extent that it becomes impractical.

[5. Examination of mechanoluminescence by metal ions other than Pr ³⁺ ]
Next, the stress luminescence when doped with metal ions other than Pr ³⁺ described above was examined. Specifically, regarding Li _1.00 NbO ₃ : Eu ³⁺ _0.01 , Li _1.00 NbO ₃ : Er ³⁺ _0.01 , and Li _1.00 NbO ₃ : Nd ³⁺ _0.01 , the above [2. Examination of Li _x NbO ₃ : Pr ^{3 +} _y (x = 1, 0 ≤ y ≤ 0.1)], a cylindrical resin pellet (diameter: 2.5 cm, height: 1.5 cm) in which the calcined sample and resin are mixed. Was prepared and used as a stress-stimulated luminescent material, and evaluated by the stress-stimulated luminescence evaluation system. The measuring method was to apply a vertical load (1000N) to the resin pellets and measure the emission intensity at that time with a photon sensor. The results are shown in FIG.

As can be seen from FIG. 10, stress luminescence was detected in all of Li _1.00 NbO ₃ : Eu ³⁺ _0.01 , Li _1.00 NbO ₃ : Er ³⁺ _0.01 , and Li _1.00 NbO ₃ : Nd ³⁺ _0.01 .

[6. Example of use of stress-stimulated luminescent material]
As described above, the stress-stimulated luminescent material according to the present embodiment emits light in response to extremely small stress and strain, and in particular, it emits light even with a minute strain of 100 μst or less. It can be said that it is characteristic.

Such a stress-stimulated luminescent material according to the present embodiment can be applied to, for example, high-sensitivity measurement of stress with respect to minute strain.

In addition, since it is possible to emit light if there is a strain of several tens of μst, it is also possible to measure the stress of constituent members such as the axle of a nanomachine, and to visualize changes in stress acting inside cells with light. Conceivable.

That is, it is considered that the force that causes a strain of several tens of μst in a nanomachine or the like is a force of about 1 to 1000 pN (a force on the order of pN), and the components of the nanomachine that perform stress measurement emit mechanoluminescence according to the present embodiment. If the material is arranged, the stress-stimulated luminescent material can respond to a strain of several tens of μst, so that light emission can be obtained by the strain. This is clear from the results shown in FIG. 6, and it can be said that the stress-stimulated luminescent material according to the present embodiment can detect a force on the order of pN.

Further, if the stress-stimulated luminescent material according to the present embodiment is placed inside or outside a cell that expands and contracts, such as a muscle cell, light emission corresponding to the expansion and contraction of the cell causes light emission of stress and movement over time inside and outside the cell. It is also possible to observe by luminescence and to know the strength of stress and motion from the intensity. Until now, the distribution of predetermined substances inside and outside the cell has been detected by light, but there is no example of visualizing the force and movement applied inside and outside the cell, and it can be said that it is extremely epoch-making. That is, the stress-stimulated luminescent material according to the present embodiment can be used as a single-phase stress-stimulated luminescent material using a piezoelectric as a base material, which can emit light with high sensitivity even with a minute force due to stress, molecular motion, or natural vibration. have.

As described above, according to the stress-stimulated luminescent material according to the present embodiment, a part of Li constituting the crystal of LiNbO ₃ is replaced with at least one metal ion selected from rare earth metal ions and transition metal ions. Therefore, it is possible to provide a single-phase mechanoluminescent material using a piezoelectric material as a base material, which can emit light with high sensitivity even with a small amount of stress.

Finally, the description of each embodiment described above is an example of the present invention, and the present invention is not limited to the above-described embodiment. Therefore, it goes without saying that various changes can be made according to the design and the like as long as the technical idea of the present invention is not deviated from the above-described embodiments.

Claims (5)

Represented by the general formula Li _x NbO ₃ : My, in which some of the Lis constituting the LiNbO ₃ crystal are replaced by at least one metal ion M selected from Pr ³⁺ , _Er ³⁺ , and Eu ³⁺ . A stress-stimulated luminescent material having a non-stoichiometric composition, characterized in that x> 1-y, 0.001 ≤ y ≤ 0.1 , and 0.99 ≤ x ≤ 2.4 . A stress-stimulated luminescent material in which the stress-stimulated luminescent material according to claim 1 is dispersed in a predetermined matrix material. Use of the stress-stimulated luminescent material according to claim 1 for detecting a force of 1000 pN or less by luminescence. Use of the stress-stimulated luminescent material according to claim 1 for detecting minute strains of 100 μst or less by luminescence. A niobium compound, a lithium compound, and a compound of at least one metal selected from praseodymium, erbium _, and europium are mixed and fired. It has a non-chemical quantitative composition represented by the general formula Li _x NbO ₃ : My substituted with at least one metal ion M selected from Pr ³⁺ , Er ³⁺ , and Eu ³⁺ , and _x >. A method for producing a stress-emitting material having 1-y and 0.001 ≤ y ≤ 0.1 , wherein the molar ratio of niobium atom to lithium atom is 1: 0.99 to 2.4 . Production method.

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