JPH0667786B2 - Method for manufacturing translucent ceramics - Google Patents

Description

The present invention relates to a method for producing a translucent ceramic, and more particularly to a method for producing a translucent ceramic made of lanthanum-modified lead zirconate titanate (hereinafter referred to as PLZT).

(Prior Art) In recent years, PLZT translucent ceramics have been attracting attention as an electro-optical material that replaces single crystals, because they exhibit a large electro-optical effect and a light scattering effect that can be controlled by an electric field. This P
LZT translucent ceramics are generally manufactured by the hot pressing method in order to obtain dense and homogeneous ones. It is difficult to increase the area and mass production, and the equipment is expensive. Therefore, an atmosphere firing method that does not use a hot press at the time of firing has been proposed. For example, Journal of American Ceramic Societ
y, Vol. 55, No. 11, pp. 541-544, L. M. Bra
A metal alkoxide solution was mixed with wn at a predetermined mixing ratio to obtain a hydroxide powder, which was calcined at 500 ° C. and then cold pressed, and the molded body was covered with a powder of the same material as that,
The method of calcination in oxygen at a temperature of 1050-1175 ° C for 4 hours or more is also the Journal of American Ceramic Societ.
y, Vol. 56, No. 2, pp. 91-96, Gary S. Snow
The PLZT powder obtained by the oxide mixing method or the chemical precipitation method was pressure-molded as it is, and after it was put in a container, an atmosphere forming powder was filled, and it was kept at 1200 ° C. for 60 hours while flowing oxygen gas. A method of firing is disclosed.

(Problems to be Solved by the Invention) However, in the former method, an alkoxide must be generated using expensive metal lanthanum, and the same material as the PLZT translucent ceramic material is used as the atmosphere material. Therefore, there is a problem that the raw material is expensive and the product cost is high. In the latter method, the mixed powder of PbZrO ₃ and PbO is used as the atmosphere material, so it is cheaper, but because the firing temperature is high, PbO evaporates during firing when the molded body becomes large and becomes insufficient. However, it is difficult to obtain a desired composition.

(Means for Solving Problems) In order to solve the above problems, the present invention provides Pb, La, Z
A precipitate formed by reacting r and Ti ions in an aqueous solution containing hydrogen peroxide is heat-treated to prepare a porous ceramic material made of PLZT, while Pb, La, Z
An atmosphere material made of PLZT having substantially the same composition as the translucent ceramics material is prepared by mixing and firing the oxides of r and Ti or compounds of those elements that become oxides by firing at a predetermined ratio and firing the translucent light. Embedding a molded body obtained by molding a powder of a conductive ceramic material in the powder of the atmosphere material,
It is characterized in that it is fired at 1080 to 1150 ° C. in an oxygen stream.

In the method of the present invention, P is used as the translucent ceramic material.
The starting material is inexpensive and has a constant composition because the precipitate produced by reacting ions of b, La, Zr and Ti in an aqueous solution containing hydrogen peroxide is heat-treated. This is because the product (1) is easily obtained, a calcined powder having a small particle size is obtained, and the firing temperature is low. This translucent ceramic material is, for example, Pb,
La, Zr, and Ti nitrates or chlorides are dissolved to form an aqueous solution containing each ion. These aqueous solutions are mixed in the presence of hydrogen peroxide, and an alkaline solution is added to adjust the pH.
It can be produced by precipitating the composite peroxide by adjusting it to 9 or more, filtering this precipitate, and then heat treating it at a temperature of 100 ° C. or more.

In this case, the reason why the pH is set to 9 or higher is to stabilize the composition of the product. As the alkaline solution to be added for pH adjustment, any solution such as sodium hydroxide solution, potassium hydroxide solution, aqueous ammonia can be used. Further, the amount of hydrogen peroxide is suitably 0.1 times or more in molar ratio with respect to 1 mol of PLZT to be produced, in order to obtain a stable composition. The heat treatment temperature is such that hydrogen peroxide present in the composite peroxide is almost completely removed as water.
It may be at least 00 ° C. As the porous ceramic material, it is usually preferable to use a material which is calcined at about 750 ° C. for about 2 hours and then pulverized into powder.

The composition of the PLZT powder thus obtained is represented by the following general formula.

Pb _1-x La _x (Zr _1-y Ti _y ) O _{1-x / 4} O ₃ (in the formula, represented by 0.04 ≦ x ≦ 0.25, 0.05 ≦ y ≦ 0.95) Lead nitrate, lanthanum nitrate, zirconium oxychloride and titanium tetrachloride are used as starting materials for the light-sensitive ceramics material powder. A solution containing the same may be used, or zirconium oxychloride or titanium tetrachloride may be used instead of the nitrate according to the following formula.

ZrOCl ₂ + NH ₄ OH → Zr (OH) ₄ Zr (OH) ₄ + HNO ₃ → Zr (NO ₃ ) ₄ TiCl ₄ + NH ₄ OH → Ti (OH) ₄ Ti (OH) ₄ + HNO ₃ → TiO (NO ₃ ) ₂ In this case, the titanium solution is generally easily hydrolyzed and difficult to prepare, but it can be stabilized by the coexistence of hydrogen peroxide, and a predetermined composition can be obtained.

If chloride is used in the absence of hydrogen peroxide, lead ions will be converted to hydroxy chloride to precipitate, and a complex peroxide having the desired composition cannot be obtained. is necessary.

The translucent ceramic is obtained by pressing the powder thus obtained, burying it in an atmosphere material, and then immersing it in an oxygen stream at a temperature of 1080 to
It is manufactured by firing at 1150 ° C. This atmosphere material is an oxide mixed method, that is, Pb, La, Zr and T.
The oxide or carbonate of i is mixed at a predetermined ratio so as to have the same composition as the translucent ceramics material, and a material obtained by a method of firing this is used. Pb is a stoichiometric composition ratio It is preferable to increase the amount by a suitable amount.

INDUSTRIAL APPLICABILITY In order to obtain desired optical properties, the present invention can be fired at a relatively low temperature by using a transparent ceramics material powder having a desired composition ratio obtained at low cost by a chemical refining method, and an oxide. By using an atmosphere material having the same composition as that of the raw material powder obtained by the mixing method, it is possible to prevent the composition from changing during firing and to inexpensively produce a large-area translucent ceramic. .

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

(Example) Lead nitrate (Pb (N
O ₃ ) ₂ ), lanthanum nitrate (La (NO ₃ )) with a purity of 99.99%
₃ ), titanium tetrachloride (TiCl ₄ ) having a purity of 99.95% and zirconium oxychloride (ZrOCl ₂ ) having a purity of 99.9%.
In accordance with the composition formula: Pb _0.91 La _0.09 (Zr _0.65 Ti _0.35 ) _0.9775 O ₃ , and Pb was weighed so as to have an excess of 0.3 atomic%,
Lead nitrate, lanthanum nitrate and zirconium oxychloride are dissolved in pure water while heating to about 600 m, and 0.3
Titanium tetrachloride solution containing molar hydrogen peroxide and pure water and H ₂
O ₂ 1.7 mol was added to make the total amount about 1. Aqueous ammonia was added to adjust the pH to 9, the precipitate formed was filtered, washed with water and dried. This precipitate was calcined at 750 ° C. for 2 hours, then wet-milled and dried to a particle size of 0.1.
A raw material powder of transparent ceramics having a size of .about.0.2 micron was obtained. As a result of examining this raw material powder by X-ray diffraction, it was confirmed that it was a completely crystalline PLZT.

Separately, lead oxide (PbO), lanthanum oxide (La ₂ O ₃ ), zirconium oxide (ZrO ₂ ), and titanium oxide (TiO ₂ ) are used as starting materials, and the composition formula: Pb _0.91 La _0.09 ( According to Zr _0.65 Ti _0.35 ) _0.9775 O ₃ , Pb was weighed so as to have an excess of 0.3 at%. This raw material powder was calcined at 900 ° C. for 2 hours, wet-milled and dried to obtain an atmosphere material powder made of PLZT.

The light-transmitting ceramic material powder was pressure-molded into pellets having a diameter of 12 mm, a thickness of 2 mm and a density of 4 g / cm ³ . Then, as shown in FIG. 1, 45 g of the atmosphere material powder produced by the above-mentioned oxide mixing method was mixed with about 120 cc of alumina crucible.
Put in (1), embed the pellet (2) in the atmosphere material powder (3), lightly cover the mouth of the alumina crucible with the alumina plate (4), set the alumina crucible in the furnace (5), A sample of translucent ceramics was obtained by firing at a temperature shown in Table 1 for 25 to 100 hours while flowing oxygen gas into the furnace at a flow rate of 0.5 / min. The temperature was raised at 4 ° C./min, the temperature was lowered to 900 ° C. at 3 ° C./min, and thereafter, the temperature was naturally cooled.

Both surfaces of the transparent ceramics samples 1 to 8 thus obtained were mirror-polished to have a thickness of 1.2 mm and a wavelength of 0.632.
The transmittance was measured using a light beam of 8 microns. The results are shown in Table 1.

Further, as a comparative example, the transmittances of Comparative Samples 9 and 10 which were prepared by pelletizing the atmosphere material powder as a raw material powder and firing the same as in the case of using the raw material powder produced by the chemical refining method and polishing The results of the measurement are shown in Table 1.

As is clear from the results in Table 1, according to the method of the present invention, sufficient translucency can be obtained even if the firing temperature is low, but PLZT produced by the oxide mixing method is used as the translucent ceramic material powder. When used and fired at a temperature of 1110 ° C., no translucency is obtained. This difference is caused by the fact that the transparent ceramic material powder produced by the chemical refining method is PLZT produced by the oxide mixing method.
It is presumed that this is because the composition is more uniform, the particle size is smaller, and the reactivity is better than that of powder.

The sample 5 obtained by firing at 1110 ° C. for 100 hours
Also, when the macrostructure of Comparative Sample 10 was examined by an electron micrograph, the method of the present invention showed that the particle size was about 5 microns and almost no residual pores were recognized, but the comparative example had a particle size of 6 microns. The presence of residual bores was fairly large.

(Effect of the invention) As described above, according to the method of the present invention, the lanthanum-modified lead zirconate titanate produced by the chemical refining method using an inexpensive starting material is used as the raw material powder for the light-transmitting ceramics. The powder of lanthanum-modified lead zirconate titanate having almost the same composition as the translucent ceramics prepared by an oxide mixing method using a cheaper oxide as a raw material can be fired at a relatively low temperature. Combined with this, it is possible to manufacture a translucent ceramic having a desired composition and at the same time, to reduce the product cost. Also,
Since only press molding is required, there is no dimensional limitation as in the hot pressing method, and it is possible to produce a large-area translucent ceramic, and it is possible to obtain an excellent effect such as mass production.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view showing an arrangement state in a furnace during firing in the method of the present invention. 1-alumina crucible, 2-pellet, 3-atmosphere material powder, 5-furnace.

Claims (3)

[Claims] 1. A translucent ceramic material comprising lanthanum-modified lead zirconate titanate is prepared by heat-treating a precipitate formed by reacting Pb, La, Zr and Ti ions in an aqueous solution containing hydrogen peroxide. On the other hand, Pb, La, Z
An atmosphere material made of lanthanum-modified lead zirconate titanate having substantially the same composition as the translucent ceramics material is prepared by mixing oxides of r and Ti or compounds of those elements which become oxides by firing at a predetermined ratio and firing. A molded body prepared by molding the powder of the translucent ceramics material is embedded in the powder of the atmosphere material, and the mixture is placed in an oxygen stream of 1080-115.
A method for producing a translucent ceramic, which comprises firing at 0 ° C. 2. The light transmissive ceramic material contains more Pb than the stoichiometric composition ratio.
A method for producing a translucent ceramic according to the item. 3. The atmosphere material is Pb based on a stoichiometric composition ratio.
The method for producing a translucent ceramic according to claim 1 or 2, which contains a large amount of.