JPH07119415B2 - Terbium-tellurium oxide and method for producing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a fluorescent material containing a rare earth-tellurium oxide as an active ingredient, which has excellent fluorescent properties, and a method for producing the novel rare earth-tellurium oxide.

2. Description of the Related Art Conventionally, a compound crystal in which a rare earth ion is substituted and solid-dissolved as an activating ion has been used as a high color rendering, high brightness phosphor, a solid laser material, or the like. In such a solid solution, the fluorescence of the rare earth ions can be observed regardless of the type of the host crystal, but it is necessary to increase the concentration of the rare earth ions in order to improve the fluorescence efficiency. However, on the other hand, when the ion concentration is increased, the interaction between ions begins to occur, and the excited energy leaks to other transition processes without becoming the expected fluorescence, so-called "concentration quenching of fluorescence". Is significant. Therefore, in this type of phosphor, the concentration of rare earth ions is at most 2-3 mol%, and when the concentration is higher than this, the luminous efficiency is remarkably reduced. Moreover, it is technically difficult to uniformly form a solid solution of a certain low concentration of ions in the host crystal. For example, in the development of a high-power laser material such as garnet or alumina which is a host crystal, crystal perfection and homogeneity due to the addition of rare earth ions are often a problem.

Therefore, the development of a new rare earth pure phosphor, which becomes a phosphor or a light emitter practically used as a flat display material or a recording medium or as a light source, which has been demanded with the recent rapid progress of the optical information related technology. Is considered to be indispensable, and the development of compounds with high luminous efficiency, which are composed of rare earth ions, has been investigated. NdP ₅ O ₁₄ , LiNd ₄ P ₄ O _{12, and the} like are known as compounds found from such a background. However, in the case of these phosphate-based compounds, there are problems in stability with respect to humidity and heat resistance, and the fact is that they have not reached the stage of practical development.

On the other hand, rare earth-tellurium oxides, especially R₂Te_FourO
₁₁A compound having a composition of (R is a rare earth element) is M.J.Re
Journal of the Less-Common Metals by dman16p.40
7-p.413 (1968), N.V.Ovcharenko et al., Optico-Mekh
ani−cheskaya PromThreep.37-p.40 (1971), V.V.Safo
nov et al., Russian Journal of Inorganic Chemistrytwenty five
(3) Weak fluorescence was reported in p.482-p.483 (1980).
It is known to show characteristics, but rare earth elements
R containing terbium as an element₂Te_FourO₁₁Type compound and its firefly
No optical properties have been reported. Also, such as C. Parada
Inorganica Chimica Acta111p.197-p.199 (1986)
Is Ln₂Te_FourO₁₁The compound represented by (Ln = Ce, Pr, Tb)
Although shown, there is no description of the fluorescent properties.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention The present invention meets the above-mentioned requirements, is easy to manufacture, has excellent luminescent properties and stability, and has a high rare earth ion concentration,
It is an object to provide a novel rare earth compound fluorescent material.

Means for Solving the Problems The present invention provides a chemical formula (Y _1-x Tb _x ) ₂ Te _4-y O _11-2y (provided that 0.01
≦ x ≦ 1, 0 ≦ y ≦ 0.25), which is a fluorescent material containing a terbium-tellurium oxide as an active ingredient. The present invention also provides a terbium-tellurium oxide represented by the chemical formula Tb ₂ Te _4-y O _11-2y (where 0 <y ≦ 0.25), or a chemical formula (Y _1-x Tb _x ) ₂ Te
It is a terbium-tellurium oxide represented by _4-y O _11-2y (where 0.01 ≦ x <1, 0 ≦ y ≦ 0.25).

The present invention also includes (a) Te or Te oxide, and (b) Tb or Tb.
There is provided a method for producing the above terbium-tellurium oxide, characterized in that the oxide and (c) Y or Y oxide, if desired, are mixed in an approximately stoichiometric ratio and heat-treated to react.

Action Tb ₂ Te ₄ O ₁₁ has lattice constants a = 1.25 nm, b = 0.512 nm, c = 1.
It has a crystal structure belonging to the monoclinic system of 61 nm and β = 106 ° C. Table 1 shown in Example 1 shows the results of powder X-ray diffraction of this compound. Tb ₂ Te _4-y O _11-2y also _{showed the} same crystal structure in the range of 0 <y ≦ 0.25. It was confirmed to be taken. When y> 0.25, this crystal form cannot be retained, and it is considered that hexagonal Tb ₂ TeO ₆ is generated. In addition, Tb ₂ Te _4-y O
A compound in the form of (Y _1-x Tb _x ) ₂ Te _4-y O _11-2y in which a part of _11-2y is substituted with Y has the same crystal structure.

The compounds represented by the above general formula are all high-efficiency green phosphors and exhibit extremely high fluorescence intensity despite having a high rare earth ion concentration of about 33 mol%, for example, Tb ₂ Te ₄ O. The emission intensity of ₁₁ is 10 times or more that of the R ₂ Te ₄ O ₁₁ compound containing no Tb described in the above document.

FIG. 1 is an emission spectrum of Tb ₂ Te _4-y O _11-2y measured using ultraviolet light having a wavelength of 375 nm as excitation light. As shown in the figure, each peak is ⁵ D ₄ → ⁷ F ₆ , ⁵ D ₄ → ⁷ F ₅ ,
It is considered to belong to each energy transition of ⁵ D ₄ → ⁷ F ₄ .

A compound obtained by substituting a part of Tb with Y also exhibits strong luminescence, and its intensity changes depending on the amount of substitution. Figure 2 shows the formula (Y _1-x
Tb _x ) ₂ Te _4-y O _11-2y (0.01 ≦ x ≦ 1) In the Y-substituted _compound , the wavelength of about 55 when the concentration x of Tb ³⁺ changes.
The change in intensity of 0 nm fluorescence (corresponding to the ⁵ D ₄ → ⁷ F ₅ transition) is shown. The horizontal axis represents the Tb mole fraction, and the vertical axis represents the relative emission intensity. As is clear from this figure, this fluorescence is Tb
Concentration quenching does not occur with respect to the ³⁺ ion concentration, and the intensity increases as the Tb ³⁺ ion concentration x increases. This is because the conventional activated phosphor, in which Tb ³⁺ as a activating ion is solid-dissolved in the mother crystal, has the maximum intensity at a Tb ³⁺ concentration of 2 to 3% due to concentration quenching. It has a peculiar property as compared with the fact that the luminous efficiency is extremely lowered when the value of is higher.

It also has good moisture resistance, and is superior in this respect to a known rare earth phosphate compound which is a pure phosphor.

The terbium-tellurium oxide of the present invention is produced by solid phase reaction of each component metal or its oxide. As the oxide raw material, in the case of Tb and Y, tertiary oxide, 47 oxide, etc.
For Te, use TeO ₂ or the like. Each raw material has a stoichiometric ratio, that is, a metal atomic ratio of Te: Tb: Y = 4: 2x: 2 (1-
x) are mixed so that the ratio becomes x. To react these raw materials, for example, they are mixed using a ball mill, dried and pulverized, and then heat-treated at a temperature and for a time sufficient for the reaction between the components. The reaction temperature is 650 ° C. or higher, preferably about 750 to 850 ° C., and the reaction time is 3 to 40 hours, although it depends on the temperature.

For example, when Tb ₄ O ₇ and TeO ₂ are heat-treated, it is considered that the reaction represented by the following reaction formula occurs.

1 / 2Tb ₄ O ₇ ＋ 4TeO ₂ → Tb ₂ Te ₄ O ₁₁ + 1 / 4O _{2 If the} heat treatment temperature is relatively high,
TeO ₂ is released.

Tb ₂ Te ₄ O ₁₁ → Tb ₂ Te _4-y O _11-2y + yTeO ₂ Therefore, depending on the heat treatment conditions, some TeO ₂ is produced from the oxide of the complete (Y _1-x Tbx) ₂ Te ₄ O ₁₁ form. Depleted oxide (Y _1-x Tb
x) ₂ Te _4-y O _11-2y (0.01 ≦ x ≦ 1, 0 <y ≦ 0.25) is obtained. It should be noted that the heat treatment decomposes into Tb ₂ TeO ₆ or the like when the heat treatment is performed at a high temperature for a long time, so that it is necessary to appropriately select the reaction conditions.

When the compound of the present invention is made into a single crystal, the emission intensity is dramatically improved. The growth of a single crystal is performed by a usual flux method or the like.

When the terbium-tellurium oxide of the present invention is used as a fluorescent material, it is used as a phosphor film by forming it as a molded body or powder, or by supporting it on an activated carrier powder, or by coating it on a substrate. You may mix with other pigments.

Example 1 TeO ₂ and Tb ₄ O ₇ were mixed at a molar ratio of about 8: 1, ethanol was added, and the mixture was wet-mixed in a ball mill, dried, and ground. The obtained powder was placed in an alumina crucible and fired in a resistance heating furnace in air at 750 ° C. for about 12 hours,
A white powder was obtained.

The chemical composition of this powder was analyzed by an energy dispersive X-ray microanalyzer and inductively coupled plasma emission spectroscopy, and the crystal phase was analyzed by powder X-ray diffraction. As a result, a compound corresponding to the formula Tb ₂ Te ₄ O ₁₁ was obtained. It was The crystal form has a lattice constant of a = 1.25 nm, b = 0.512 nm, c = 1.61n
It belongs to the monoclinic system with m and β = 106 °. The results of powder X-ray diffraction of this compound are shown in Table 1.

Next, the emission characteristics of this compound were investigated. When this compound was irradiated with ultraviolet rays having a wavelength of 375 nm as an excitation source using a xenon lamp, it emitted green fluorescence. The emission spectrum is shown in FIG.

Example 2 TeO ₂ and Tb ₄ O ₇ were mixed at a molar ratio of about 9: 1, and calcined at 800 ° C. for about 24 hours in the same manner as in Example 1 to obtain a white powder.

The product has the formula Tb ₂ Te _4-y O _11-2y by elemental analysis and X-ray diffraction.
Was confirmed to be the corresponding compound, and the X-ray diffraction pattern showed the same crystal form as in Example 1.

This compound showed strong fluorescence as in Example 1. The shape of the fluorescence spectrum was almost the same as in Example 1.

Example 3 _To the powder of Tb ₂ Te _4-y O _11-2y obtained in Example 2, 10 wt% lithium chloride was added as a flux to form a pellet, which was melted at 700 ° C. for 3 days and gradually cooled. And diameter 2-3 μm
A hexagonal plate crystal having a size of about 3 was obtained. Using this as a seed crystal, a mixture of Tb ₂ Te _4-y O _11-2y powder and 10% by weight of lithium chloride was melted at 700 ° C for 6 days, and then gradually cooled in a furnace to obtain a diameter of about 10 μm. A hexagonal plate-shaped Tb ₂ Te _4-y O _11-2y single crystal was obtained.

The fluorescence intensity was about 4 times that of Example 2 at an emission wavelength of 550 nm.

Example 4 TeO ₂ , Tb ₄ O ₇ and Y ₂ O ₃ were used as raw materials, the total ratio of Tb and Y and the atomic ratio of Te were approximately 1: 2, and the atomic ratio of Tb and Y was 1: 0 to.
The mixture was variously mixed up to 0.01: 0.99 and heat-treated at 750 ° C. for 3 hours to cause reaction.

The obtained compound was (Y _1-x Tb _x ) ₂ Te _4-y O _11-2y (x is 0.01
It is determined by the mixing ratio of Y and Te within the range of ≤x≤1. ) Was confirmed. The crystal form was the same as in Example 1.

When the Tb ³⁺ ratio of this compound changes, the wavelength is 550 nm.
The change in the fluorescence intensity was investigated and shown in FIG.

The emission spectrum of this Y-substitute has almost the same shape as in FIG. 1, but when x <0.1, emission from the ⁵ D ₃ order is observed near 400 to 450 nm. The emission spectrum of (Y _0.99 Tb _0.01 ) ₂ Te _4-y O _11-2y excited by ultraviolet rays having a wavelength of 375 nm is
It is shown in FIG.

EFFECTS OF THE INVENTION The fluorescent material of the present invention has excellent emission characteristics, and has a high concentration of Tb ³⁺ ions as compared with a conventional compound crystal in which Tb ³⁺ ions are substituted and solid-solved. Nevertheless, it has the characteristics that the luminous efficiency is high, the difficulty of uniformly dissolving a small amount of ions is eliminated, and a homogeneous compound can be easily produced.
It also has excellent stability and can be used for various lamps, solid-state lasers,
Applications as optical materials such as optical sensors and optical recording materials are expected.

[Brief description of drawings]

FIG. 1 is an emission spectrum of Tb ₂ Te ₄ O ₁₁ excited by ultraviolet rays having a wavelength of 375 nm. Figure 2 shows (Y _1-x Tb _x ) ₂ Te _4-y O
_11-2y shows the change in fluorescence intensity at a wavelength of 550 nm when the ratio of Tb ³⁺ was changed, and FIG. 3 shows (Y _0.99 Tb _0.01 ) ₂ Te _4-y O ₁₁ It is an emission spectrum of _-2y .

Claims (4)

[Claims] 1. A chemical formula (Y _1-x Tb _x ) ₂ Te _4-y O _11-2y (however, 0.0
Terbium represented by 1 ≦ x ≦ 1, 0 ≦ y ≦ 0.25)
A fluorescent material containing tellurium oxide as an active ingredient. 2. The chemical formula Tb ₂ Te _4-y O _11-2y (where 0 <y ≦ 0.2
A terbium-tellurium oxide represented by 5). 3. The chemical formula (Y _1-x Tb _x ) ₂ Te _4-y O _11-2y (however, 0.0
Terbium represented by 1 ≦ x <1, 0 ≦ y ≦ 0.25)
Tellurium oxide. 4. (a) Te or Te oxide, and (b) Tb or Tb.
The method for producing a terbium-tellurium oxide according to claim 3, wherein the oxide and (c) Y or the oxide thereof are mixed in a substantially stoichiometric ratio and heat-treated to react.