JPS596833B2 - Ferroelectric transparent porcelain composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides A(BνBゝ)03-PbZr03-PbTi
03 (However, A■ Ba, Sr, CaB'=Li, Na
The present invention relates to a new and useful ferroelectric transparent porcelain which is a three-component solid solution composed of B''=Nb, Ta) and has excellent translucency and a large electro-optical effect.

Conventional electro-optical element materials such as water-soluble crystals ADP and KD
P, oxide single crystal LiNb03 with oxygen octahedron, BN
N, SBN, etc. are known, but the former water-soluble crystals have poor water resistance and heat resistance and lack industrial applicability, while the latter oxide single crystals are of high quality and difficult to grow as large single crystals. The disadvantage is that it is not suitable for mass production.

In recent years, ferroelectric ceramics sintered under pressure at high temperatures have excellent translucency despite being polycrystalline, and have the property of operating in the same way as optical uniaxial crystals when polarized by applying an electric field. Therefore, it is expected to be applied as an electro-optical element. These transparent porcelain materials are PbZr03 and P
Bi203, La203, Sn0 in the solid solution of bTiO3
It is a porcelain composition with a perovskite structure that is pressure-sintered with a few percent of 2, etc. added thereto. Among them, the ones that are considered to be particularly excellent as optical materials are G, H, and Hae from the United States.
, C.H. Land, abbreviated as PLZT (Pbl-xLax(ZryTi1-y)1-
103) (see Japanese Patent Publication No. 48-42318). This is made by adding lanthanum oxide (La203) to PZT, that is, zircon/lead titanate atomic ratio of 5 to 25%.It is easy to manufacture, has high transparency, and has a large electro-optic effect, so it is used in optical shutters, optical memories, and optical Numerous studies have been reported on the application of elements to modulators, optical deflectors, etc.
However, when lanthanum (La) is used, its structural formula is Pbl
As shown by -xLax(ZryTi1-y)1-'03, there is a lattice defect on the ZrTi side. Actually, sintered PLZT differs slightly from the above structural formula and has lattice defects on the Pb side as well. (G, S, Snow, Fabr
icationofTransparentElec
troopticPLZTCeramicsbyAtm
osphereSyntering, J.Amer,
Cer, Soc, Vo156A2, p91-96) Therefore, lead (Pb) tends to evaporate and the expensive alumina mold used for hot pressing is easily corroded, resulting in low mass productivity. Furthermore, if excess lead is not completely evaporated and remains, the transparency will be significantly reduced. Transparent porcelain containing La is colored pale yellowish brown, but this also has the disadvantage that its light transmittance tends to decrease significantly on the short wavelength side of the visible region. Additionally, traditional transparent porcelain takes on a black tinge when exposed to white light for long periods of time.

This is a photochromism effect originating from a structure with lattice defects, and the light transmittance in the visible region of an optically polished sample is greatly reduced. In contrast, the present invention uses lead zirconate (PbZrO3) and lead titanate (PbTiO3).
) with lithium strontium niobate as the third component,
The above problems are solved by creating a ternary solid solution containing lithium barium niobate, lithium strontium tantalate, lithium barium tantalate or sodium strontium niobate, sodium barium niobate, sodium strontium tantalate, and sodium barium tantalate. The present invention provides an electro-optical material with excellent sinterability, translucency, and color tone. The present invention is {
A(B57B'3A)03}, {Pb(K, Til-ρ
03} When it hails 1-o, x=0.05~0.30
, y is a ternary solid solution in the range of 0.1 to 0.9.

Here, A is one of the A group elements consisting of Ba, Sr, and Ca, B' is one of the B7 group elements consisting of Li, Na, and K, and B // is the B group element consisting of Nb and Ta. It is made up of only one person. This has a different structure from conventional transparent porcelain containing lanthanum (La). That is, the present invention uses lanthanum (La
), and each structural element is maintained at a stoichiometric composition. Therefore, lead evaporates during sintering and the alumina hot press mold is less likely to be corroded, improving mass productivity. Furthermore, by using the above-mentioned third component, the pale yellow-brown color characteristic of conventional transparent porcelain is significantly reduced, and the light transmittance in the short wavelength region of the visible region is greatly improved.

Furthermore, the present invention does not exhibit the blackening caused by the photochromism effect, which is a drawback of conventional transparent porcelain containing La, and there is no change in color tone or decrease in light transmittance even if left under white light for a long time. .

In addition, ferroelectric transparent porcelain generally has high light transmittance in the paraelectric phase or antiferroelectric phase, but in the ferroelectric phase, which has optical anisotropy due to its crystal structure, the light transmittance decreases due to scattering. This causes a problem when used as an optical element in this phase.

However, the three-component solid solution ceramic of the present invention has excellent light transmittance even in a composition that belongs to the ferroelectric phase, so it is an effective material when used as a primary electro-optical element or when used in a piezoelectrically activated state. be. The present invention will be described in detail below based on Examples.

Lead monoxide (PbO) and strontium carbonate (SrCO3) with a purity of 99.5% are used as starting materials for manufacturing the porcelain of the present invention.
Barium carbonate (BaCO3) Zirconium oxide (ZrO
2) Titanium oxide (TiO2) and lithium carbonate (L
i2CO3) or sodium carbonate (Na2CO3) or potassium carbonate (K2CO3) and purity 99.9
% of niobium pentoxide (Nb2O5) or tantalum pentoxide (Ta2O5) was used. The manufacturing process is as follows. First, these raw materials are weighed so as to have the desired composition, distilled water is added, and wet mixing is performed using a ball mill for about 2 hours. Next, primary calcination is performed at 820° C. for 2 hours to prepare a reaction product. Further, the mixture was dry mixed in a mortar for 2 hours to make the particle size uniform. A very small amount of water is added to this powder, and it is molded into a cylinder with a diameter of 25 wm and a thickness of 10 wm using a hydraulic press using a mold at a pressure of 150 kg/Cd, and left for several days to evaporate the water. This sample was placed in a cylindrical alumina mold with an inner diameter of 40 wm and set in a hot press furnace. The firing conditions by hot press are 1 x 10 up to 900℃.
The temperature is raised in a vacuum of -2T0rr, and oxygen is introduced at 900°C to create an oxygen atmosphere. Apply a pressure of 60 kg/Cd at 900°C and set the final pressure to 120kg/Cd at 1220°C.
Hold for 8 hours and sinter.

The temperature increase rate is 300℃/H9OO℃~1 below 900℃
At 220°C, the rate is 200°C/h. The porcelain thus obtained is cut to a thickness of 0.2 to 0.5 m and finished by optical polishing. Tables 1 and 2 show the porcelain material of the present invention {Sr
M? Mζ03}｛Pb(ZryTil-y)03}1
-o (However, M/=Li, Na, KM″=Nb, Ta
) I6 and materials in which part of Pb (or Sr) in these compositions is replaced with Sr (or Pb) are shown below. The meanings of the symbols in this table are as follows. ε33T/ε0 tanδ Kr Dielectric constant (measured at 1kHz after polarization at room temperature) Dielectric loss (measured at 1kHz after polarization at room temperature) Radial coupling coefficient Tc t Temperature per unit (°C) Thickness of optically polished sample (Tvn) Tr Light transmittance (%, value at wavelengths of 400 nm and 600 nm) As is clear from this table, the composition of the present invention has high transmittance even in compositions belonging to the ferroelectric phase (sample numbers 1 to 12, 15, 16, etc.). Light efficiency is relatively high on the short wavelength side.

This is believed to be because the yellow-brown coloring and blackening due to photochromism, which are characteristic of conventional ferroelectric transparent porcelain, are drastically reduced in the present invention. Figure 1 shows Sr(Li-N)
b3A) Phase diagram of 03-PbZrO3PbTiO3 ternary solid-solution. This figure shows {Sr(Li-Nb%)03
}x{Pb(ZryTil-y)03}1-x, the vertical axis is Sr(Li)(Nb-i)0 for the whole
3, that is, x, and the horizontal axis is PbzrO3
and PbTiO3, that is, y. The region I in this phase diagram is rhombohedral (ferroelectric), and the region I is tetragonal (
Ferroelectric (ferroelectric) has a cubic (paraelectric) structure; the shaded area is the antiferroelectric phase, and depending on the composition ratio, it consists of rhombohedral, tetragonal, or a mixed crystal of these and cubic crystals. ing. Figure 2 is 300-1000n measured by spectrophotometer.
This is an example of light transmittance measured in a wavelength range of m.

This sample had x=0.130, y=0.700 (sample number 7 in Table 1), and was optically polished on both sides to a thickness of 0.25 m. The light transmittance is close to 100%, excluding reflection loss at the front and rear two surfaces of the thin plate. Furthermore, since there is little yellowish-brown coloration, the light transmittance shows a sharp rise in the vicinity of 400 nm. In Figure 3, A=SrB'=Li, B'=Nb, x=
The electric field dependence of the birefringence of a sample having a composition of 0.150y=0.550 (sample number 4 in Table 2) is shown.

The measurement was performed at 633 nm using a Babinet Soleil corrector, and the electrodes were 1T! on both sides of the optically polished sample. r!
Gold was deposited at intervals of n. The linear change of the effective birefringence Δn with respect to the applied voltage is called the first-order aperture optical effect (Pockels effect). The effective birefringence Σ due to the first-order electro-optic effect is expressed as Δn=-(IA)NtrcE3.

Here, E3 is the applied electric field, n1 is the (effective) refractive index in the direction perpendicular to E3, and RO is the first-order (effective) electro-optic coefficient of the transverse effect. This figure shows the change in bi with respect to the electric field after the polarization is once saturated. From this, the electro-optical constant is R. =5.05×10-1 m/V. This constant is large enough to be put to practical use compared to other optical crystals. Figure 4 shows A=SrB'=Na, B'2=N
The electric field dependence of the effective birefringence of bx=0.135, y=0.600 (sample number 15) is shown.

In this case, μ changes in proportion to the square of the electric field (E). That is, this shows a second-order electro-optic effect (force-effect). Effective birefringence due to secondary electro-optic effect
It is given by (X)n↑RE\.

Here R is the second-order (effective) electro-optic coefficient. In the case of this sample, R=4.54×10 −16 d/V2 is given. This value is comparable to that of conventional optical materials, and is promising as a secondary electro-optic material. Finally, in the present invention, the composition ratio is set to x=0.05~0.30y=0.1~0.
The reason why the range of 9 was selected is that a composition outside this range would have a low light transmittance and a small electro-optical effect, making it unsuitable for practical use.

As mentioned above, the ferroelectric transparent porcelain of the present invention has excellent translucency and color tone, has a large electro-optic effect, can be applied to a wide range of electro-optical devices, and has other advantages such as low lead evaporation and easy manufacture. This has a remarkable industrial effect.

[Brief explanation of drawings]

The drawings are diagrams showing physical characteristics of embodiments of the present invention.
The diagram shows lithium strontium niobate-lead zirconate-
A phase diagram of a lead titanate ternary solid solution, FIG. 2 is a diagram showing wavelength transmittance characteristics, and FIGS. 3 and 4 are diagrams showing changes in effective birefringence with respect to electric field.

Claims (1)

[Claims] 1 A(B'_1_/_4B″_3_/_4)O_3-
A three-component solid solution composed of PbZrO_3-PbTiO_3 is made into a solid solution of [A(B′_1_/_4B″_3
＿／＿４）O_３〕＿x〔Pb(Zr_yTi_1_-
_y)O_3]_1_-_x, the strength is characterized by having a blending ratio in which the values of x and y are in the range of x = 0.05 to 0.30 and y = 0.1 to 0.9. Dielectric transparent porcelain composition, where A is selected from the group of Ba, Sr, and Ca, B' is selected from the group of Li, Na, and K, and B'' is selected from the group of Nb and Ta. He is the chosen one.