JPH04265277A - Device for calcination with atmosphere - Google Patents

Abstract

PURPOSE:To cause no high temp. reaction even in longtime calcination and to make the warpage generated during calcination small. CONSTITUTION:Bottom powder 34 formed by a composition which is about the same as a PLZT plate 20 as object to be calcined is formed on the upper surface of a setter 18. On the upper surface of the bottom powder 34, mounted is the PLZT 20 plate as object to be calcined. During calcination, the bottom powder 34 prevents the PLZT plate 20 from coming into direct contact with the setter 18 to check the high temp. interaction of the PLZT plate 20 with the setter 18. The bottom powder 34 prevents heat from being transferred from the setter 18 side to the PLZT plate 10 to decrease friction between the PLZT plate 20 and the setter 18 as well as to make the temp. difference small between the upper and lower surfaces of the PLZT plate 20. Thereby the warpage of the PLZT plate 20 during calcination can be made small.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention involves firing an object to be fired, such as a PLZT plate, in a predetermined atmosphere in order to create a translucent ceramic wafer (for example, a PLZT wafer) having an electro-optical effect. This invention relates to an improvement of an atmosphere firing device.

0002

[Prior Art] PLZT (for example, (Pb0.91La0.09)) (Z
r0.65Ti0.35)O3) has a region exhibiting electro-optic effects such as a memory effect, a first-order electro-optic effect, and a second-order electro-optic effect. Utilizing this electro-optic effect characteristic, it is expected to be applied to various devices such as display devices, optical modulators, and optical shutters. With the development of these various devices, a PLZT wafer with a large area and a thickness of several hundred μm to several mm has become necessary. In order to create such large-area PLZT wafers, conventional equipment has been used as a device suitable for firing objects to be fired such as PLZT plates.
An atmosphere firing apparatus as shown in FIG. 4 has been known.

That is, double heat-resistant containers (for example, alumina crucibles (also called saggers)) 12 and 14 are installed in the firing furnace 10.
into the inner heat-resistant container 12 with atmospheric powder (for example, Pb
Add O+ZrO2)16,16. And the setter
A plurality of sets 18, 20, . . . are placed in the heat-resistant container 12, with the PLZT plate 20 as the object to be fired placed on the underlay 18. At this time, vertically adjacent setters 18, . . . are spaced at a predetermined interval by support stands 22 and 22, . Hold. Then, oxygen (O2) as an atmospheric gas is introduced between the double heat-resistant containers 12 and 14 from the outside through the atmospheric gas introduction pipe 24, and baking is performed in an oxygen atmosphere. Setter 18 is made of magnesia (MgO) or zirconia (Zr).
It is formed from a substrate whose main component is O2).

0004

[Problems to be Solved by the Invention] However, the conventional atmosphere firing apparatus shown in FIG.
℃ for a short time of up to about 50 hours, this was not a problem, but when firing for a longer time than that, a high temperature reaction occurred between the contact surfaces of the setter 18 and the PLZT plate 20 during firing, and the firing There is a problem in that electro-optic effect defects are formed on the PLZT wafer, and these defects cause crossed Nicol light leakage (for example, star light leakage). Further, the upper surfaces of the PLZT plates 20, .
, the temperature difference between the upper and lower surfaces of the PLZT plate 20 during firing increases, and the fired product (for example, PLZT sintered body) 30 of a predetermined thickness (for example, 1 mm) obtained by firing, The depth of the warp F as shown in Figure 5 on the top surface of...
There was a problem in that large warpage (for example, F=300 μm) occurred, making it difficult to flatten it by polishing after firing. The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide an atmosphere firing apparatus that does not cause high-temperature reactions even during long-time firing and can reduce warping that occurs during firing. .

[0005]

[Means for Solving the Problems] The present invention provides a heat-resistant container in a firing furnace, a setter and an object to be fired to be placed on the setter, and an atmospheric gas inside the heat-resistant container. In an atmosphere firing apparatus which performs firing by introducing The method is characterized in that the object to be fired is placed on the top surface of this bed powder.

[0006]

[Operation] The object to be fired is placed on a setter through a bed of flour and placed in a heat-resistant container, and atmospheric gas is introduced into the heat-resistant container to perform atmospheric firing. During this firing, the bedding powder formed between the object to be fired and the setter is made of almost the same composition as the object to be fired, and blocks direct contact between the object to be fired and the setter. This prevents high-temperature reactions between the fired product and the setter. In addition, since the powder is compacted and has a flat upper surface, high-temperature reactions between the material to be fired and the powder are also prevented. In addition, the bed powder formed between the object to be fired and the setter blocks the heat transmitted from the setter side to the object to be fired, reducing the temperature difference between the top and bottom surfaces of the object to be fired, and also reduces the temperature difference between the top and bottom surfaces of the object. Since the friction between the setter and the setter is reduced, warpage of the object to be fired during firing can be reduced.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of the present invention, and in this figure, the same parts as those in FIG. 4 are given the same reference numerals. In FIG. 1, 10 is a firing furnace, and inside this firing furnace 10, there is a double heat-resistant container (for example, an alumina crucible (also called a sagger)) 1
2 and 14 are provided. the double heat-resistant container 12;
Inside the heat-resistant container 12 of the containers 14, atmospheric powder (for example, PbO + ZrO2) 16, 16 is placed, and setters ( Underlay) 18,... are included. The setter 18 is made of magnesia (MgO) with a purity of 99.9%. Reference numeral 24 denotes an atmospheric gas introduction pipe, and this atmospheric gas introduction pipe 24 introduces oxygen (O2) as an atmospheric gas between the double heat-resistant containers 12 and 14 from the outside, and can perform firing in an oxygen atmosphere. That's what I do.

[0008] On the upper surface of the setter 18, (Pb
0.91La0.09) (Zr0.65Ti0.35)
A PLZT powder 32 having a composition of O3 is compacted by the method shown in FIG. 2 to form a bed powder 34 having a flat upper surface. That is, first, (a) in Figure 2
A sieve 36 of a predetermined mesh (e.g. #60) as shown in
PLZT powder 32 with a predetermined particle size or less is transferred to setter 1 using
Then, as shown in FIG. 2(b), a predetermined load (for example, a load of pushing by hand) is applied to the PLZT powder 32 using a flat plate 40 with paraffin paper 38 interposed therebetween.
is compacted to form a bed powder 34 with a flat upper surface. PLZT plates 20, . . . as objects to be fired are placed on the upper surface of the bed powder 34, . The PLZT board 20 is formed, for example, as follows. That is,
Using a ball mill, (Pb0.91La0.09)(
PLZT with the composition Zr0.65Ti0.35)O3
Powder, binder 5-10% by weight, plasticizer 2-5% by weight
, 0.2% by weight of a dispersant, and 60 to 90% by weight of a solvent to form a slurry for a predetermined period of time, and this slurry is filtered, defoamed, and made into a grease using a doctor blade sheet molding machine. Prepare a green sheet, cut this green sheet to an appropriate size, and remove the binder (for example, at 500°C for 1 hour).
0 hours of debinding).

Next, the operation of the above embodiment will be explained. The PLZT board 20 is placed on the setter 18 via the bedding powder 34 and placed in the inner heat-resistant container 12, and between the inner and outer heat-resistant containers 12 and 14, atmospheric gas is supplied from the outside through the atmospheric gas introduction pipe 24. The firing furnace 10 is operated for a predetermined period of time (for example, 50 to 10 hours).
0 hours) at a predetermined temperature (e.g. 1200°C to 1300°C).
) to perform firing in an oxygen atmosphere. During this firing, the bedding powder 34 formed between the PLZT board 20 and the setter 18 is made of the same composition as the PLZT board 20, and the PLZT board 20 and the setter 18 are
Since direct contact between the PLZT plate 20 and the setter 18 is blocked, a high temperature reaction between the PLZT plate 20 and the setter 18 is prevented. Moreover, bed powder 34
Since the PLZT powder 32 is compacted and the upper surface side is flat, high-temperature reaction between the PLZT board 20 and the bedding powder 34 is also prevented. In other words, if the powder remains, a high-temperature reaction may occur between the PLZT plate 20 and the PLZT powder 32 during firing, but if the PLZT powder 32 is compacted and the upper surface side is flat, Since it is 34,
This is because it is difficult to react. Therefore, a translucent PLZT sintered body (
A baked product) was obtained.

Furthermore, the bedding powder 34 between the PLZT board 20 and the setter 18 is transferred from the setter 18 side to the PLZT board 20.
This reduces the temperature difference between the top and bottom surfaces of the PLZT board 20 by blocking the heat transmitted to the setter.
Since the friction with 18 is reduced, P during firing is reduced.
Warpage of the LZT board 20 can be reduced. That is, when the conditions are the same as those of the conventional example shown in FIG. 4 except for providing the bed powder 34, the predetermined thickness (
As shown in FIG. 3, the depth F of the warp on the top surface of the PLZT sintered body (for example, 1 mm) is less than half (F=130 μm) of the conventional example (F=300 μm shown in FIG. 5). there were. Therefore, it becomes easy to flatten the surface by polishing after firing. Generally, it is said that if the depth F of the warp is 150 μm or less, it is easy to flatten it by polishing after firing. In the above embodiment, the padding powder formed on the top surface of the setter was made of the same composition as the object to be fired, but the present invention is not limited to this, and it may be made of almost the same composition as the object to be fired. Any material may be used as long as the formed powder is compacted and the upper surface side is made flat.

[0011]

[Effects of the Invention] Since the atmosphere firing apparatus according to the present invention is constructed as described above, it has the following effects. (b) Form a padding made of almost the same composition as the material to be fired on the top surface of the setter, and place the material to be fired on top of this foundation powder to ensure direct contact between the material to be fired and the setter. Since it is shut off, a high temperature reaction between the object to be fired and the setter can be prevented even if the firing time becomes long. Furthermore, since the powder is compacted to form a flat upper surface, high-temperature reactions between the object to be fired and the powder can be prevented even if the baking time is long. Therefore, it is possible to prevent defects in electro-optic properties from occurring in the fired product. (b) The bed powder formed between the object to be fired and the setter blocks the heat transmitted from the setter side to the object to be fired during firing, reducing the temperature difference between the top and bottom surfaces of the object to be fired. Since the friction between the object to be fired and the setter is reduced, it is possible to reduce the warpage of the object to be fired during firing. Therefore, polishing of the fired product can be facilitated.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an embodiment of an atmosphere firing apparatus according to the present invention.

FIG. 2 is an explanatory diagram showing a method of forming the bedding powder of FIG. 1;

3 is an explanatory diagram illustrating the depth of warpage of a fired product fired with the apparatus of FIG. 1. FIG.

FIG. 4 is a configuration diagram of a conventional device.

5 is an explanatory diagram illustrating the depth of warpage of a fired product fired with the apparatus of FIG. 4. FIG.

[Explanation of symbols]

10... Firing furnace 12, 14... Heat resistant container (alumina crucible) 16... Atmosphere powder (PbO+ZrO2) 18... Setter 20... PLZT plate (object to be fired) 24... Atmosphere gas introduction pipe 30, 50... PLZT sintered body (sintered) Item) 32...PLZT
Powder 34...Bed powder O2...Oxygen (atmosphere gas)

Claims (1)

[Claims] Claim 1: A heat-resistant container is provided in a firing furnace, a setter and an object to be fired to be placed on the setter are placed in the heat-resistant container, and atmospheric gas is introduced into the heat-resistant container to perform firing. In the atmosphere firing apparatus, the setter
Pressing powder made of substantially the same composition as the object to be fired on the upper surface to form a flattened powder with a flat upper surface side;
An atmosphere firing apparatus characterized in that the object to be fired is placed on the upper surface of the bed powder.