JPS5912618B2 - Manufacturing method of electro-optic ceramics - Google Patents

Description

Detailed Description of the Invention The present invention provides AB03 (A is a monovalent or divalent cation, B
relates to a manufacturing method for making transparent ferroelectric ceramics having a perovskite crystal structure expressed by average valence, pentavalent or tetravalent cations.

Transparent ferroelectric ceramics have excellent electro-optical properties and are extremely useful as materials for various light modulation elements or image storage elements.

Conventionally, barium titanate (BaTiO3) and lead titanium zirconate solid solution (PbTlO3-PbZrO3) are known as ferroelectric ceramics.
These materials have been put to practical use as dielectric materials, capacitors, and piezoelectric materials. However, since these ceramic materials have almost no light transmittance, their use is limited to the above-mentioned specific fields, and there has been no application to electro-optical fields. Recently, transparent ferroelectric ceramics that scatter less light have been developed. This ceramics is
A conventionally known piezoelectric ceramic Pb(Zr,Ti)03 having a composition of (Pb,La)(Zr,Tl)03
It is the only existing transparent ferroelectric ceramic with 5 to 10 at% of La added to it. Pb(Zr, Ti
)03 alone exhibits almost no light transmittance, but the reason why the light transmittance is significantly increased by adding a small amount of La to it as a solid solution has not been elucidated to date. Therefore, in order to obtain transparent ferroelectric ceramics, it was considered essential to add La as a solid solution. In the present invention, the first condition for the above-mentioned ceramic to become transparent is that the optical anisotropy of the crystal grains constituting the ceramic is small, and the second condition is that light absorption in the visible light region is small. Thirdly, the present invention provides a new manufacturing method for making ferroelectric ceramics transparent without including La by satisfying the requirement that there are no residual pores that cause light scattering in the ceramics. It is.

That is, the ferroelectric ceramic of the present invention has (1) an ABO8 type having a perovskite crystal structure (A is a monovalent or divalent cation Ll, Na, K, Pb, Ca,
B is a cation M whose average valence is 5 or 4
g, W, Sc, Nb, In, Ta, Cd, Zr, Ti,
A combination of Ni and Na), or a solid solution ferroelectric material of (2) to (self) shown below; (2) (1-x
) KNbO3-XKTaO3O. 3〈X＜0.6, (3
) (1-x)PbTiO3-XCaTiO3O. 4O
〈x〈0.65, (4) (1-x)BaTiO3-X
SrTiO3O. O5〈x＜0.6(5) (1-X)
BaZrO3-XCaZrO3O. Ol〈x〈0.17
, (6) (Pbl-X, Bax) (Hfy, TiO-,
)0s0.15〈x〈1.0,0kuy〈0.9, (7)
(Pbl-X, Srx) (Hfy, Til-,)08
0.15〈xku0.7,0kuy〈0.9, (8) (1
-x) BaTiO3-XBaSnO. J.O. O5〈x〈
0.20(9) (1-x)NaNbO3-XKTaO
,O. O6〈x〈0.6101(1-x)PbTiO8
-XCaSnO3O. 2O〈x＜0.60συ (1−
x) PbTiO3-XSrSnO,O. 2O<x<0.
35 (generation) (Pbl-X, Bax) (Snl-,,Ti
y) 030.2x〈1.0, 0.1〈y〈0.803
(1-x)PbTlOs-, ([JilA,Cel/2
) TiO8O. 55〈x＜0.65(self)(1-x)P
bTlO3-x(Lil/2, NbV)TiO3O. 5
Ox<0.6505) (1-?C)PbTiO3-
XPb(MglA,Wl/2)QO. 5〈xku1.0(
to) (1-x) PbTiO3-x (K1/2, Bi1A
)ZrqO. 25 x〈0.45a7) (Cax,S
ry, Baz) TiO3 However, x+y+z=10〈x〈0
．． 6,0.2<y<1,0<z<0.7. ．． 08) (
Cax, Bay, Pbz) TiO8 However, x+y+z=1
0.45x<0.55,0〈y〈0.35・,0.2
z<0.55, and these are completely different from conventional transparent ferroelectric materials.

Furthermore, in order to remove residual pores that become scattering centers in the above substances and improve translucency, solid solution powder or oxalate powder produced by coprecipitation was used as the ceramic raw material with the above composition, and an oxygen-filled atmosphere was used. The sintering conditions are as follows: This is a limitation due to the strength of the die that occurs when using an alumina mold in an oxygen stream.Also, the sintering time is at least 1 hour, and 5 to 200 hours is considered to be appropriate in practice. The details of the present invention will be explained.

Example As a starting material for the electro-optic ceramics of the present invention, PbO with a purity of 99.9% or more and a powder particle size of <2 μm,
MgO, OdO, NiO, WO, Sc, O3, ce2
O3tsuNd2O3jBi2O3raSnO2yzrO2?
TlO2FNb2O5FTa2O5, Li2COS, N
Weigh a2OO3, K, and CO3 according to a predetermined chemical formula.

The above powder was mixed in a pole mill using distilled water as a solvent, and after evaporation to dryness, the mixture was heated at 700°C to 130°C, l for 12 hours.
Calcinate in an oxygen stream. After cooling, this calcined powder is coarsely ground in an agate mortar or the like, and mixed again in a ball mill using acetone as a solvent. By heating this powder at 700'C for 1 hour in an oxygen stream, acetone adsorbed on the powder is removed by evaporation. The calcined powder is pressure-molded using a steel die at a pressure of 350Kf/C7t to a size of 15 mm in diameter and 8 mm in height. This green compact was charged into one die made of alumina, set in an electric furnace, and hot press sintered. In the sintering method used here, first, an alumina die loaded with a sample was set in an electric furnace, and then heated for 20 minutes.
After evacuating to a vacuum level of 0 to 400'Cll [2T0rr for 60 minutes, the inside of the furnace was replaced with oxygen gas, and then heated in an oxygen stream to 1000 to 1450°C, 1 to 200 hours, 50 to 700K9 /CTIIO) Pressure hot press sintering method. The hot-pressed sample is removed from the alumina die using a diamond core drill and cut into desired dimensions with a diamond cutter, and both surfaces of the sample are optically polished.

Table 1 shows the manufacturing conditions and light transmittance of the composition of the present invention.

In Table 1, in the compositions indicated by the sword seal, acetate is used as a raw material for monovalent, divalent and rare earth metals, other raw material oxides are sufficiently dispersed in this aqueous solution, and oxalic acid is added to form the oxides. A mixed precipitate was synthesized.

The above precipitate was calcined to decompose the siolate and react with the oxide to obtain a solid solution powder, which was then hot-pressed and sintered. As explained above, according to the present invention, when ABO3 type ceramics having a perovskite crystal structure are made transparent, each crystal grain constituting the ceramic has small optical anisotropy and low absorption. By selecting such a ceramic composition and hot-press sintering the ceramic in a manner that eliminates light scattering centers, it is possible to obtain a ceramic having significantly higher light transmittance than conventional ceramics.

The ceramic sintered bodies obtained by the embodiments of the present invention have excellent electrical and optical properties, and exhibit excellent performance when used in various image memory devices, light modulation devices, optical devices, etc. However, the industrial effects of the present invention are extremely large.

Claims (1)

[Claims] 1 General formula ABO_3 (where A is Li, Na, K,
Pb or Ca, B is Mg, W, Sc, Nb, In,
Ta, Cd, Zr, Ti and Ni with an average valence of 4
A perovskite ceramic having a composition represented by a combination selected to be valent or pentavalent, or a solid solution ferroelectric material having a composition represented by the following general formula, (1-x)KNbO_3-xKTaO_3 (however,
0.3<x<0.6), (1-x)PbTiO_3-x
CaTiO_3 (however, 0.40<x<0.65),
(1-x) BaTiO_3-xSrTiO_3 (0.05<x<0.6), (1-x)BaZrO_3
-xCaZrO_3 (where 0.01<x<0.17
), (Pb_1_−_xBa_x) (Hf_yTi_1
____y) O_3 (however, 0.15<x1.0, 0≦
y<0.9), (Pb_1_−_xSr_x)(Hf_
yTi_1_-_y)O_3 (however, 0.15<x<
0.7, 0≦y<0.9), (1-x)BaTiO_3
-xBaSnO_3 (where 0.05<x<0.20
), (1-x) NaNbO_3-KTaO_3 (however, 0.06<x<0.061), (1-x)PbTiO
_3-xCaSnO_3 (0.20<x<0.60),
(1-x)PbTiO_3-xSrSnO_3 (0.20<x<0.35), (Pb_2_-_xBa
_x) (Sn_1_-_yTi_y)O_3 (However,
0.2<x<1.0, 0.1<y<0.8), (1-x
)PbTiO_3-x(Li_1_/_2Ce_1_/
_2) TiO_2 (0.55<x<0.65)
(1-x)PbTiO_3-x(Li_1_/_2Nb
_1_/_2) TiO_2 (0.50<x<0
．． 65), (1-x)PbTiO_3-xPb(Mg_
1_/_2W_1_/_2)O_3 (however, 0.5<
x<1.0), (1-x)PbTiO_3-x(K_1
_/_2Bi_1_/_2) ZrO_2 (however, 0.
25<x<0.45), (Ca_xSr_yBa_z)
TiO_3 (where x+y+z=1, 0<x<0.6
, 0.2<y<1, 0<z<0.7), (Ca_xBa
_yPb_z) TiO_3 (however, x+y+z=1,
0.45<x<0.55, 0<y<0.35, 0.2<
y < 0.55), by hot press sintering, the oxide of each metal element or a compound of a metal element that can be changed into an oxide by heating and has a purity of 99% is required to satisfy these general formulas. Powder with a particle size of .9% or more and a particle size of 2 μm or less at a pressure of 50 to 700 Kg/cm^2 and a temperature of 900 to
A method for producing electro-optic ceramics characterized by hot press sintering at 1450° C. for 5 to 200 hours.