JPS6055470B2 - Method for manufacturing oxide ceramics - Google Patents

Description

Detailed Description of the Invention The present invention relates to a manufacturing method using hot isostatic pressing of oxide ceramics such as soft ferrite and piezoelectric ceramics, and relates to a manufacturing method that prevents cracks that occur during hot isostatic pressing. .

In the production of such oxide ceramics, a hot isostatic pressing method is adopted in order to remove internal pores, prevent excessive crystal grain coarsening due to crystal growth, and achieve high density.

This hot isostatic pressing method includes the capsule method, glass mold method, and pre-sintering method, but the first two methods have problems in terms of cost and productivity, so the density of the material to be processed is adjusted to the theoretical density. 94% or more, so that the pores of the treated material become closed,
A common pre-sintering method is to pre-sinter the molded material to be treated and then hot isostatically press it.

When the compact is pre-sintered in this pre-sintering method, a surface strain layer is formed on the surface of the sintered body, and internal strain accumulates due to the difference in composition between the inside of the sintered body and the surface layer. When a compact is subjected to hot isostatic pressing, the large stress accumulated on the main surface causes cracks to occur in the processed material.

The above cracking is particularly noticeable in the case of a large sintered body having dimensions of 10TfUft or more on each side and a volume of 15d or more. The object of the present invention is to provide a manufacturing method that does not cause cracks in the treated material when subjecting oxide ceramics to hot isostatic pressing using a pre-sintering method.

That is, this invention is made of oxide ceramics such as soft ferrite and piezoelectric ceramics, each side having a dimension of 10W7l.
As described above, a molded body having a volume of 15c7ll or more is pre-sintered, the surface layers of at least two opposing main surfaces of this sintered body are polished away by at least O, Iwun per surface, and then subjected to hot isostatic pressing. This is a method for producing oxide ceramics. In hot isostatic pressing, the dimensions of the molded material to be processed are plate-shaped materials with each side of 1- or more and a volume of 15 d or more because the molded material under the above conditions has no internal strain during pre-sintering. This is because cracks occur in the sintered body during the hot isostatic pressing process due to accumulation of particles, and the larger the size and volume of the compact, the deeper the surface strain layer that needs to be removed by grinding after sintering.

Next, the compact with the above dimensions is pre-sintered, but the sintering conditions vary depending on the material of the compact; in the case of soft ferrite,
When the material to be treated is Mn-Zn ferrite, oxygen 0.5
~1150 elemental C~13 in an inert gas atmosphere containing ~10%
A temperature condition of 500C is preferred, and in the case of Ni-Zn ferrite, a temperature of 1150C to 1250'C in an oxygen atmosphere is preferred.

In addition, in the case of piezoelectric ceramics, the heating temperature is 1100°C in an oxygen atmosphere.
Temperature conditions of ~1250'C are preferred. In this invention, at least two opposing main surfaces of a pre-sintered sintered body are ground. Although the depth of the surface strain layer varies depending on the material, at least the surface layer of the two opposing main surfaces is ground by 0.1
It is necessary to remove more than Tm. That is, 0.1Tn!
If less than n is removed by polishing, a surface strain layer will remain and cracks will occur during hot isostatic pressing. In the case of soft ferrite, since the surface strain layer to be removed by polishing is deep, it is preferable to remove the surface layer with a thickness of 0.2 Tnm or more by polishing. Furthermore, polishing the surface layer over the entire surface of the sintered body is extremely effective in preventing cracking during hot isostatic pressing. Removing this will prevent cracking during hot isostatic pressing. The sintered body from which the surface layer has been ground is then subjected to hot isostatic pressing, preferably at a temperature of 1000° C. to 1300° C. and a pressure of 400 kg/C7lf to 2000 kg/d.

Examples according to the present invention will be shown below to clarify its effects.

Example 13 The raw materials for Mn-Zn ferrite were MnCO326.8 mol%, ZnO2l. 2 mol%, F
Weighed and blended 52 mol% of e2O3, mixed, calcined and pulverized, 60 ro x ω Junkari 2 mfn 1 volume 43.2 cf! l
Breath molded into a block.

3 This molded body 1
After the binder was removed from the sample, it was sintered for 2 hours at 130 liters in nitrogen gas containing 1% oxygen.
The obtained sintered body is 60T10n×607127! The two main surfaces of the specimen were ground down by 0.5 m per side.

4.Then, the ground sintered body was subjected to hot isostatic pressing at a temperature of 1100° C. and a pressure of 1200 k9/d. Next, soft ferrite obtained by the conventional manufacturing method in which a sintered body whose surface was not polished after sintering was subjected to hot isostatic pressing under the same conditions, and soft ferrite obtained by the above-mentioned method of the present invention were generated. An evaluation test was conducted based on the number of cracks. The results are shown in Table 1. ) [Example 2] NiOl3.
Weighed and blended 5 mol% of ZnO, 2 mol% of ZnO, and 49.5 mol% of Fe2O3, mixed and pulverized after calcining, 48Tnf
nX6-x12 pieces, volume? ．． Breath molded into a 56d block.

After the molded body 10- was subjected to a binder removal treatment, it was sintered for 2 hours at 1200'Cl in an oxygen atmosphere.

The obtained sintered body is 48wt x 60T! The two main surfaces of St were polished by 0.4Tt01t per side.

Next, the sintered body after grinding was heated at a temperature of 1200°C and a pressure of 100°C.
Hot isostatic pressing was performed under the conditions of 0k9/c#f.

Next, soft ferrite obtained by the conventional manufacturing method in which a sintered body whose surface was not polished after sintering was subjected to hot isostatic pressing under the same conditions, and soft ferrite obtained by the above-mentioned method of the present invention were examined for cracks that occurred. An evaluation test was conducted based on the number of pieces. The results are shown in Table 2. [Example 3] PbTiO, 53 mol%, as a raw material for piezoelectric ceramics,
Weighed and blended 47 mol% of PbZrO3, mixed and molded it, calcined it, then finely pulverized it to a powder of 60% by weight. ×6h×12? , volume 43.2
Breath molding was done on block a1.

After the binder was removed from this molded body, 1230'Cl was sintered for 2 hours in an oxygen atmosphere. Two main surfaces of 6 Cym x 6 h of the obtained sintered body were
．． 2wrm group was deleted.

Next, the sintered body after grinding was heated at a temperature of 1200°C and a pressure of 100°C.
Hot isostatic pressing was performed under the condition of 0k9/cl.

Next, a piezoelectric ceramic obtained by the conventional manufacturing method in which a sintered body whose surface was not polished after sintering was subjected to hot isostatic pressing under the same conditions, and a piezoelectric ceramic obtained by the above-mentioned method of the present invention were produced. An evaluation test was conducted based on the number of cracks. The results are shown in Table 3. As is clear from Tables 1 to 3, the present invention can prevent the occurrence of cracks during hot isostatic pressing and improve yield, which is extremely effective.

Claims (1)

[Claims] 1. A molded body made of oxide ceramics with each side dimension of 10 mm or more and a volume of 15 cm^3 or more is pre-sintered, and the surface layers of at least two opposing main surfaces of this sintered body are coated per surface. A method for producing oxide ceramics, which comprises performing a hot isostatic press treatment after grinding away 0.1 mm or more. 2. The method for producing oxide ceramics according to claim 1, wherein the surface layer is removed by polishing to a depth of 0.2 mm or more per surface after preliminary sintering of the molded body made of soft ferrite.