JPS63291843A - Production of optical ceramics - Google Patents

Abstract

PURPOSE:To obtain optically homogeneous (Sr,Ba)Nb2O6 ceramics having a high density and light transmitting properties, by preparing a modified Sr.Ba oxide raw material powder having a particle size of submicron order and excellent dispersibility, synthesizing readily sinterable (Sr,Ba)Nb2O6 powder having a high bulk density and sintering the resultant (Sr,Ba)Nb2O6 powder. CONSTITUTION:A solution containing Sr and Ba and an adequate amount of Nb is mixed with a precipitate forming agent, such as NH3, to form a coprecipitated substance, which is then dried and calcined at 800-1,400 deg.C. The resultant modified Sr.Ba oxide powder which is powder having a particle size of submicron order with extremely rare aggregation is used as a raw material and blended with the residual Nb compound of the aimed (Sr,Ba)Nb2O6 composition by a dry method. The obtained raw material having excellent powder characteristics and a particle size of submicron order is molded and sintered. Thereby the aimed optically homogeneous optical ceramics, consisting of (Sr,Ba) Nb2O6 and having extremely high density and high light transmitting properties are obtained even by omitting operation, such as hot-pressing or not isostatic process (HIP).

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to optical ceramics, and more particularly to a method for producing strontium barium niobate (Sr,Ba)NbzOh. (Sr, Ba)NbtO6 is expected to find wide-ranging applications as optical ceramics such as polarizing elements, optical shutters, and image storage elements.

[Conventional technology]

(Sr, Ba)NbzO as optical ceramics
Conventionally, a is typically manufactured by sintering raw material powder obtained by calcining a mixed powder of strontium carbonate, barium carbonate, and niobium oxide using hot pressing, HIP (hot gas pressure sintering), etc. has been done.

(Problems to be Solved by the Invention) Among the raw material powders of (SrtBa)NbtO, strontium carbonate and barium carbonate raw material powders are extremely likely to agglomerate. (Sr+Ba) by dry method such as
When NbzOh raw material powder is created, its average particle size is 1~
2- or more. This level of particle size (Sr, Ba)
When NbzO6 raw material powder is used, it is difficult to obtain optically uniform (Sr, Ba)NbzOi with high density and high transparency.

The present invention was made to solve the above-mentioned drawbacks in the dry synthesis of (Sr, Ba)NbzOa, and its purpose is to create a submicron-grade modified strontium/barium oxide raw material powder with good dispersibility, Using this powder, easily sinterable and high bulk density (Sr,
Ba) Nbz06 powder is synthesized, and this powder is further sintered to produce a high-density, highly translucent, optically uniform (Sr,
An object of the present invention is to provide a method for producing Nb, O, (Ba).

[Means to solve the problem]

As a result of intensive research to achieve the above object, the present inventors found that the general formula (Sr+-xBax)Nbz06, (0,2<
x <0.8> In the process of producing (Sr, Ba)Nb, Ob by a dry method, a solution containing strontium and barium and an appropriate amount of niobium is mixed with a precipitate forming solution to form a coprecipitate. , after drying, 800-1400℃
It has been found that when calcined with Using this as a raw material, the target (Sr, Ba)Nb, 0. By dry-mixing the remaining niobium compound in the composition, a submicron-level raw material powder with excellent powder properties can be easily obtained. When this is shaped and sintered, it can be heated using hot press or HIP (hot gas pressure). It has been found that extremely high density, highly transparent, and optically uniform (Sr+Ba) 2 NbzOa can be easily obtained even if operations such as sintering are omitted.

Based on these findings, the present invention was completed.

That is, the present invention provides (1) mixing a solution containing a predetermined ratio of strontium and barium and an appropriate amount of niobium with a precipitant to form a coprecipitate containing the strontium, barium, and niobium; After drying, 800 ~
(2) mixing the calcined product obtained in step (1) with a niobium compound forming the remainder of the composition of the target strontium barium niobate;
a step of calcining at 00 to 1400°C; and (3) a step (2).
The calcined powder obtained is molded and heated to 1100-1400℃
A method for producing optical ceramics, comprising the steps of: obtaining a desired strontium barium niobate sintered body.

Strontium is typically added to the solution by dissolving strontium chloride, strontium nitrate, etc. in water or alcohol, but strontium metal may also be dissolved in an aqueous acid solution.

In order to contain barium in the solution, barium chloride, barium nitrate, barium metal, etc. are similarly used.

Typically, niobium chloride is dissolved in alcohol to incorporate niobium into the solution, but niobium oxide may be dissolved in an alkaline solution or an aqueous HF solution, or metallic niobium may be dissolved in an acid aqueous solution.

The solution contains the target composition of barium strontium niobate, Sr+-xBaxNb, 0. A predetermined proportion of Sr and Ba corresponding to the above is included along with an appropriate amount of Nb. Adding niobium to this suppresses agglomeration of the strontium oxide/barium oxide powder obtained when the coprecipitate of strontium and barium is calcined. Therefore, the amount added is preferably within a range that can suppress agglomeration of the strontium/barium oxide powder.

As the precipitant, for example, organic reagents such as ammonia, ammonium carbonate, caustic alkali, oxalic acid, ammonium oxalate, amine, oxine, etc. are used.

Co-precipitation is generally carried out by gradually adding the above-mentioned solution containing strontium, barium and niobium to a solution containing a precipitant while stirring, but is not limited to this method. The coprecipitate produced is generally a complex of strontium, barium and niobium hydroxides.

The obtained coprecipitate is separated by filtration, washed, dried, and then calcined at 800 to 1400°C. The modified strontium barium particles obtained in this way are a composite of strontium oxide, barium oxide, and niobium oxide.
It is a submicron level fine powder with no agglomeration. When the calcination temperature is lower than 800°C, agglomeration occurs significantly, and when it exceeds 1400°C, the particles tend to become coarse. The calcination atmosphere is air atmosphere.

The calcined powder of the coprecipitate obtained in this way is mixed with a niobium compound corresponding to the niobium lacking in the target strontium barium niobate composition, typically niobium oxide powder, and then heated at 800 to 1400°C. Calculate it. This calcination is performed in order to realize a uniform strontium barium niobate composition. The calcination temperature varies depending on the ratio of strontium and barium, but it needs to be at least the minimum temperature at which the solid phase reaction is almost or completely completed, and within the maximum temperature range at which no significant particle growth occurs. The calcination atmosphere is air atmosphere.

The thus obtained powder having the desired composition is compacted and sintered. The sintering temperature varies depending on the content ratio of strontium and barium, similar to the calcination temperature of the mixture, but is generally within the range of 1100 to 1400°C. . 1
If it is lower than 100℃, sintering will be insufficient and high density will not be obtained.
If the temperature exceeds 1400°C, the particles may become coarse or the constituent components may volatilize. The sintering atmosphere is an oxygen gas atmosphere. The sintering method does not need to be hot pressing or HIP as in conventional methods, and a strontium barium niobate sintered body having excellent properties as an optical ceramic can be obtained by a simple sintering method.

〔Example〕

1 unit: strontium nitrate aqueous solution <0.75 taol/1 concentration) 100 cc and barium nitrate aqueous solution (0.25 m
. 12/1 concentration) and 300 cc of niobium chloride ethanol solution (0.40 soβ/l concentration) were mixed. This mixed solution was gradually added to 6N ammonia water 31 without stirring, and Sr", Ba"+ and Nb"
A hydroxide coprecipitate of was obtained. After washing and drying this, 1
Calcined at 000℃ for 4 hours to produce (Sro, ysBaa,
zs) Nb+, zo4 powder was created. This powder had submicron particles.

137.77 g of the powder obtained above and commercially available N1gO
53.164 g of s powder (average particle size 0.7 mm) was mixed in a ball mill overnight and then calcined at 1100° C. for 4 hours to obtain (Sro, tsBao, zs)NbzOb powder. The average particle size was 0.53-.

A tablet formed by molding this powder at 1 ton/d was sintered at 1350° C. for 4 hours in an oxygen gas atmosphere.

The density of the obtained (Sro, ?SBO,zs) NbzOb sintered body is 5.32 g/cnl, which is the theoretical density (5,4
28/aJ). In addition, the transmittance is
At a wavelength of 500 nm for a sample with a thickness of 0.2 m, it was 68%.

Commercially available 5rC (h powder (average particle size 0.8) + B
aCO3 powder (average particle size 0.7 mm), NbgOs powder (
Average particle size 0.74) (Sro, 7sBao, z,
)NbtOb, mixed all day and night in a ball mill, and then calcined at 1100° C. for 4 hours. A tablet formed by molding this powder at 1 ton/ffl was sintered at 1350° C. for 4 hours in an oxygen gas atmosphere. The density of the obtained sintered body was 5.08 g/cd. In addition, the light transmittance is 1 at a wavelength of 50 on- for a sample with a thickness of 0.2 tm.
It was 7%.

In addition, the powder obtained by calcining consists of large aggregates,
The average particle size could not be determined.

〔Effect of the invention〕

According to the method of the present invention, the strontium/barium oxide powder containing niobium (modified strontium/barium oxide powder) containing niobium can be made into submicron particles with extremely few secondary particles, and by using this, Thereafter, submicron grade (Sr, Ba)Nbz06 raw material powder was easily obtained by a simple dry method, and this was further used as a raw material to produce (Sr, Ba) with good translucency and high density.
The excellent effect of obtaining Nbz06 can be achieved. In addition, the following effects are also achieved.

1) Since the modified strontium/barium oxide powder obtained by calcining the coprecipitate is sufficiently dispersed, it can be supplied as a raw material powder without the need for a particular pulverization step of the calcined product.

2) The (Sr, Ba)NbzOi powder obtained by a dry method from the calcined modified strontium barium oxide powder is also obtained in a monodisperse state, and therefore has characteristics of sufficiently easy sinterability and high density even without the pulverization step. .

3) For optical electronics applications that require extremely high density and high optical uniformity (Sr, Ba) NbzOi can be produced by simple solid-phase sintering, omitting operations such as hot pressing and HIP (hot gas pressure sintering). It is possible to obtain a high density extremely close to the theoretical density, high optical uniformity, and high light transmittance.

4) By mass producing modified strontium barium oxide powder having excellent powder properties, (S r + B a ) N b 20 b of any composition can be supplied at extremely low cost.

Claims (1)

[Claims] 1. (1) A coprecipitate containing strontium, barium and niobium is formed by mixing a solution containing a predetermined proportion of strontium and barium and an appropriate amount of niobium with a precipitant. (2) mixing the calcined product obtained in step (1) with a niobium compound forming the remainder of the composition of the target strontium barium niobate; , a step of calcining at 800 to 1400°C, and (3) molding the calcined powder obtained in step (2) to 11
A method for producing optical ceramics, comprising the step of sintering at 00 to 1,400°C to obtain a desired strontium barium niobate sintered body.