JPH0798664B2 - Manufacturing method of fine powder for producing pyroelectric porcelain for infrared sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a lead zirconate titanate-lead niobate manganate (hereinafter referred to as "PZT-PMnN") system used as a pyroelectric material for infrared sensors. The present invention relates to a method for producing a PZT-PMnN-based fine powder suitable for producing a sintered body.

[Prior art]

Of the thermal infrared sensors that do not require a cooling device,
The one using the pyroelectric porcelain has been attracting attention because it has the best performance and is easy to use. Among them, the PZT-PMnN type pyroelectric porcelain is the lead zirconate titanate (hereinafter referred to as "PZ
It is superior in voltage sensitivity (Rv) to that of a system consisting only of "T").

As a method for producing such a pyroelectric porcelain, conventionally, a method of mixing powders of oxides of the respective component elements to a required composition, calcining, crushing, molding, and sintering the molded product under normal pressure has been known. Are known. However, the powder used for sintering by this method is
Since the average particle size is as large as several μm or more, the sinterability is low. As a result, the sintered body obtained by pressureless sintering has a low sintering density and the pyroelectric properties required for a pyroelectric ceramic are insufficient. Will be things. In order to improve sinterability, it is possible to add a sintering aid such as lithium to the powder and sinter under normal pressure or sinter by hot pressing.However, the sintering aid becomes an impurity. There is a problem that the pyroelectric characteristics of the porcelain obtained as a result are degraded, and there is a problem that the hot press requires an expensive and large-scale device.

Therefore, an easily sinterable PZT-PMnN-based fine powder that can obtain a pyroelectric ceramic having a dense and excellent pyroelectric property by a normal atmospheric pressure sintering method without using a sintering aid is desired. ing. In recent years, as a method for producing such fine powder, a method of simultaneously precipitating (coprecipitating) all the constituent elements from a solution in which a compound of each constituent element is dissolved in a required composition and calcining the obtained precipitate (coprecipitation method) ) Is proposed.

[Problems to be solved by the invention]

However, in the case of the above coprecipitation method, the precipitation forming ability of each element with respect to one precipitation forming liquid (for example, the solubility product of the precipitate of each element at a constant pH) is different, so that the precipitation fine particles of the same composition as the charged composition are not necessarily formed. Not always obtained,
When precipitates are formed, they tend to aggregate to form secondary particles, and as a result, the sinterability is improved but there is still a problem. Furthermore, it is desirable to use inexpensive titanium tetrachloride as a raw material compound of titanium, but since chlorine ions formed by dissolution of titanium tetrachloride react with lead to form a white precipitate, it can be used at the same time as a lead compound. However, there is a problem that expensive titanium nitrate must be used instead.

Therefore, an object of the present invention is to manufacture a porcelain having a dense and excellent pyroelectric property by an atmospheric pressure sintering method without using a sintering aid, and an easily-sinterable PZT-PMnN-based pyroelectric ceramics for infrared sensor. It is an object of the present invention to provide a method for producing fine powder for production, which is capable of easily producing fine powder having a target composition.

[Means for solving problems]

The present invention, as to solve the problems of the prior art, the general _{formula: (1-A) PbZr x} Ti (1-x) O 3 -APbMn y Nb (1-y) O
₃ [wherein A, x and y are each 0.01 ≦ A
≦ 0.3, 0.54 ≦ x ≦ 0.95, 0.25 ≦ y ≦ 0.55. ] A method for producing fine powder for producing pyroelectric porcelain for a lead zirconate titanate-lead niobate manganate-based infrared sensor having a composition represented by: 1 to 5 selected from lead, zirconium, titanium, manganese and niobium. A precipitate containing the 1 to 4 elements is generated from a solution containing the 4 elements, and then the remaining 4 to 1 of the 5 elements are dispersed in a state where the obtained precipitate is dispersed. The solution containing at least one element of at least one species to produce a precipitate containing at least one element of at least one of four to one to precipitate all of the five elements, Another object of the present invention is to provide a method for producing fine powder for producing pyroelectric ceramics for a lead zirconate titanate-lead niobate lead manganate-based infrared sensor, which comprises calcining a precipitate containing the above five elements.

In the general formula, A, x, and y are each 0.
It is necessary to manufacture the fine powder so that the ranges of 01 ≦ A ≦ 0.3, 0.54 ≦ x ≦ 0.95 and 0.25 ≦ y ≦ 0.55 are satisfied. A, x
If either one of y and y is out of the above range, the voltage sensitivity of the porcelain obtained by sintering the fine powder becomes insufficient. Also, if the proportion of lead niobate manganate is excessively increased, the pyroelectric coefficient of the porcelain obtained is increased,
As a result of the relative permittivity also increasing, the voltage sensitivity is not so improved.

The production method of the present invention is a method of performing precipitation formation in two or more steps without precipitating (coprecipitation) the five elements of lead, zirconium, titanium, manganese, and niobium simultaneously when forming the precipitation (hereinafter, "Multi-stage wet method") is used. This method can be modified in many ways by selecting the order of elements to be precipitated, the combination of elements to be coprecipitated in one step, the number of steps of precipitation formation, etc.,
To give some specific examples, among these five elements, one element is precipitated in the first step and remains in the second step.
Method of coprecipitating seed elements, conversely, coprecipitating 4 kinds of elements in the first step, precipitating 1 out of 4 kinds remaining in the 2nd step, and remaining 3 in the 3rd step There is a method of coprecipitating seeds, a method of sequentially forming precipitates in five steps for each of the five elements, and the like. Furthermore, a method of performing precipitation formation in 6 or more steps by dividing one element into a plurality of steps to form the precipitation is also included. Usually, it is general to carry out in 2 to 5 steps.

Can be used as a raw material in the production method of the present invention, Pb, Zr,
Examples of compounds of Mn, Nb and Ti include salts of organic or inorganic acids such as oxychlorides, carbonates, oxynitrates, sulfates, nitrates, acetates, formates and oxalates of these elements, and water. Examples thereof include oxides, chlorides, and oxides, but are not particularly limited thereto.

As a solvent for preparing a solution containing these compounds, water, alcohol, or a mixed solution thereof is usually used.
It is not limited to these. If it is not soluble in these solvents, mineral acid may be added to solubilize it.

Since the present invention employs a multi-stage wet method, compounds that could not be used because of poor compatibility in the conventional coprecipitation method can be used in combination. For example, the above-mentioned titanium tetrachloride can also be used if precipitation of Ti and Pb is carried out in separate steps.

The formation of the precipitate is preferably performed by mixing an aqueous solution containing the raw material compound with an excessive amount of the precipitate forming liquid. Examples of the precipitate-forming liquid used include solutions of ammonia, ammonium carbonate, caustic alkali, sodium carbonate, oxalic acid, ammonium oxalate, and organic reagents such as oxines and amines. You can select from these.

When the precipitate forming solution used in one step is the same as the precipitate forming solution used in the next step, the element containing the precipitate obtained in the previous step is used as it is in the next step. It suffices to mix the solution containing the above. In this case, since the precipitate forming solution has already been added in an excessive amount, there is no need to add it again depending on the case. In addition, if the precipitate-forming solution of the next step is different from the precipitate-forming solution of the previous step, and it is desirable that the precipitate-forming solution used in the previous step does not exist in the next step, the precipitate of the previous step is used. After the formation, the precipitate may be washed, and then the precipitation in the next step may be carried out in a state of being dispersed in a solvent or an aqueous solution containing an element to be precipitated in the next step.

The method of dispersing the precipitate in a solvent or solution is not particularly limited, and examples thereof include stirring with a normal stirrer and a method of applying ultrasonic waves.

The obtained precipitate is subjected to the subsequent calcination after washing and drying, and it is desirable to use alcohols such as ethanol for the washing, whereby aggregation during drying and calcination can be further suppressed.

The obtained precipitate is calcined in air or oxygen at 550 to 750 ° C, preferably 600 to 700 ° C.
The calcination time may be about 1-2 hours.

By this calcination, a uniform PZT-PMnN fine powder in which PMnN is solid-dissolved in PZT can be obtained. They have few secondary particles, and the average particle size is usually less than 1 μm. It is connected. If the calcination temperature is less than 550 ° C, the solid-phase reaction is not completed, and the phases of PbTiO ₃ , PbZrO ₃ , MnO, and Nb ₂ O ₅ coexist. Further, if the calcination temperature exceeds 750 ° C., grain growth becomes remarkable and easily sinterable fine powder cannot be obtained.

In order to produce a sintered body using the PMnN-PZT-based fine powder of the present invention thus obtained, preferably after pulverizing the fine powder,
It suffices to mold and sinter the molded product at 1000 to 1200 ° C. The atmosphere for sintering includes air, oxygen, or an atmosphere containing lead oxide vapor in these, but in oxygen containing lead oxide vapor. Is preferred. The sintering method may be either pressureless sintering or pressure sintering, but pressureless sintering is sufficient.

〔Example〕

 Hereinafter, the present invention will be described with reference to examples.

Example 1 General formula: (1-A) PbZr _x Ti _(1-x) O ₃ -APbMn _y Nb _(1-y) O
₃ , a predetermined amount of zirconium oxynitrate (ZrO (NO ₃ ) ₂ ), titanium chloride (TiCl ₄ ), manganese chloride for producing a porcelain having a composition represented by A = 0.033, x = 0.661 and y = 0.342. An aqueous solution in which (MnCl ₂ ) and niobium chloride (NbCl ₅ ) were dissolved was prepared. These aqueous solutions were simultaneously dropped into 5N (normal) ammonia water while stirring to form precipitates of zirconium, titanium, manganese, and niobium elements, and the precipitates were stirred for 30 minutes to sufficiently precipitate them. After the substance is formed, a predetermined amount of lead nitrate (Pb (N
An aqueous solution containing O ₃ ) ₂ ) was added dropwise, and the mixture was further stirred for 30 minutes,
A coprecipitate of zirconium, titanium, manganese, niobium and lead was obtained. After leaving this coprecipitate for about 1 hour,
After filtering, washing with water and isopropyl alcohol, vacuum drying was performed, and the obtained fine powder was calcined at 600 ° C. for 1 hour.

Regarding the fine powder thus obtained according to the production method of the present invention,
The following operations were performed in order to measure the performance of a sintered body formed by sintering it.

After pulverizing the fine powder with a ball mill, it is molded at ² t / cm ² ,
This molded product was sintered in oxygen saturated with PbO vapor at 1200 ° C. and normal pressure for 12 hours.

After measuring the sintered density of the obtained sintered body,
After polishing to a thickness of 1 mm and baking the Ag paste, polarization treatment was performed in silicone oil at 100 ° C. for 1 hour in an electric field of 50 kV / cm. The pyroelectric coefficient and the specific resistance of the sample after the polarization treatment were measured, and the sintered body was processed into a chip of 2.7 × 4 × 0.1 mm to deposit an electrode, and then the voltage sensitivity of the device at 1 Hz was measured. . The results are shown in Table 1.

Examples 2 to 7 Examples except that a solution of each raw material compound was prepared so that a porcelain having a composition in which A, x and y in the general formula shown in Example 1 have the values shown in Table 1 was obtained. Fine powder was obtained by performing the same operation as in 1, and further sintered to obtain a sintered body, and the sintered density, pyroelectric coefficient and the like were measured. Table 1 shows the measurement results thereof in each example.

Comparative Example In the above general formula, A = 0.1, x = 0.650 and y = 0.
In order to produce a porcelain having the composition represented by 333,
A predetermined amount of each oxide powder of PbO, ZrO ₂ , TiO ₂ , MnO and Nb ₂ O ₅ was mixed in a ball mill and calcined at 800 ° C. In order to measure the performance of a sintered body produced from the powder thus obtained, the powder was molded, the molded product was sintered at 1200 ° C. under normal pressure, and the obtained porcelain was processed in the same manner as in Example 1. The sintered density and pyroelectric coefficient were measured. Table 1 shows the measurement results.

[Effects of the Invention] The fine powder for producing a PZT-PMnN-based infrared sensor for pyroelectric porcelain obtained by the production method of the present invention usually has an average particle size of submicron order and few secondary particles are formed. Is excellent. It is possible to produce a fine powder for the production of PZT-PMnN-based infrared sensor pyroelectric ceramics by pressureless sintering at a relatively low temperature, and the obtained ceramics have excellent pyroelectric characteristics. Is also useful as Further, according to the production method of the present invention, it is possible to easily produce a fine powder having a desired composition for producing a PZT-PMnN-based infrared sensor pyroelectric ceramics.

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Claims (1)

[Claims] 1. A general formula: (1-A) PbZr _x Ti _(1-x) O ₃ -APbMn _y Nb _(1-y) O
₃ [wherein A, x and y are each 0.01 ≦ A
≦ 0.3, 0.54 ≦ x ≦ 0.95, 0.25 ≦ y ≦ 0.55. ] A method for producing fine powder for producing pyroelectric porcelain for a lead zirconate titanate-lead niobate manganate-based infrared sensor having a composition represented by: 1 to 5 selected from lead, zirconium, titanium, manganese and niobium. A precipitate containing the 1 to 4 elements is produced from a solution containing the 4 elements, and the obtained precipitate is dispersed in the remaining 4 to 1 of the 5 elements. The solution containing at least one element of at least one species to form a precipitate containing the at least one element of at least one of four to one to precipitate all of the five elements, and A method for producing fine powder for producing pyroelectric ceramics for lead zirconate titanate-lead niobate manganate-based infrared sensors, which comprises calcination of a precipitate containing the above five elements.