JPS63185856A - Zirconia sintered formed body - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to zirconia sintered bodies, and more particularly to solid electrolytes such as gas sensors, sintered batteries, oxygen pumps, daily necessities such as cutlery, and machines such as engines. The present invention relates to a zirconia sintered body suitable for parts.

(Prior Art) Ceramics containing clay can be easily shaped by plastic deformation. Furthermore, non-plastic ceramics containing zirconia or the like as a main component can also be molded by adding and blending an organic binder. However, since the molded bodies manufactured by these methods deform during firing, it is necessary to carry out post-processing and modification if dimensions and precision are required.

Furthermore, there is a method that uses pressure forming, which is widely used in the production of electronic and mechanical parts, but while this pressure forming method allows mass production and high-speed molding, it is difficult to uniformly fill the raw materials. If high precision is required for the construction, it is necessary to correct it by post-processing as in the existing method.

Furthermore, there is a slurry casting method as a method for easily obtaining a complicated molded body without distortion with a simple operation. but,
This cast molding method has the problem of slow working speed (poor mass productivity) and difficulty in producing high-strength, high-density sintered bodies.

On the other hand, the hot press method and hot isostatic press method, which perform molding and firing at the same time, can adjust the microstructure of the sintered body and promote densification, and in a relatively short time compared to other methods. This is an extremely effective method as it allows sintering to be completed at a lower temperature. However, it is difficult to produce complex shapes and thin products, and it is not suitable for mass production and tends to result in high product costs. As mentioned above, existing methods When trying to manufacture high-strength, dense sintered bodies using sintered bodies as raw materials, it was difficult to produce complex shapes and thin objects. Thus, there was an antinomic relationship between mechanical strength and densification and the production of complex shapes and thin objects.

(Problems to be solved by the invention) In view of the above-mentioned problems of existing methods, the present inventors have
The present invention was completed as a result of extensive research, and
The purpose is to provide a zirconia sintered body with excellent mechanical strength and density.In addition to the above characteristics, the other purpose is to provide a zirconia sintered body with a complex shape or thin shape. It is in. Further objects and effects will become apparent from the description below.

(Means for Solving the Problems) The above-mentioned object is to provide a solution to the problem by combining zirconium oxide (4) and at least one stabilizer selected from the group of ythonium oxide, cerium oxide, calcium oxide and magnesium oxide. Zirconia is produced by plastically working a calcined molded product or powder or powder molded product made of a ceramic raw material mainly composed of The ceramic raw material according to the present invention achieved by the sintered compact is zirconium oxide <zr
o. ) with a stabilizer C selected from the group of yttrium oxide (Y2O3), calcium oxide (Cab), magnesium oxide (MgO) or cerium oxide (CeO2).
The main component is a mixture of B), but additives such as sintering aids such as aluminum oxide, silicon oxide, and bismuth oxide, which are usually added to ceramic raw materials,
Or 8C, La, PI”, Nd, Pffl.

8m, Eu, Gd, Tb, DY, Ho, Er, Tm, Y
It goes without saying that rare earth oxides such as b and Lu may be added and blended in small amounts as appropriate.・Zirconium oxide (4
The amount of stabilizer () to be added to () depends on the properties required of the target zirconia sintered body, and the amount of stabilizer () to be added to ().
It varies depending on the type of B) and cannot be absolutely specified, but it is preferable to limit it to about 15 mol% at most. Preferred ranges of stabilizers () to be added to zirconium oxide are 2.0 to 10.0 mol% for yttrium oxide, 5.0 to 15.0 mol% for calcium oxide, and 5.0 to 5.0 mol% for fl magnesium. 15.0 mol%, cerium oxide 7.0-16
．． It is about 0 mol%. These ceramic raw materials may be prepared by appropriately selecting from known methods, and these methods are broadly classified into dry methods and wet methods. As a dry method, there is a method in which, for example, a predetermined amount of powder of a stabilizer such as zirconium oxide and yttrium oxide is mixed using a ball mill, pulverized, heat treated, and then mechanically pulverized. Furthermore, examples of the wet method include the following methods.

(1): A precipitant such as ammonia is added to a mixed aqueous solution of a water-soluble zirconium salt such as zirconium chloride and a water-soluble salt of a metal as a stabilizer such as yttrium chloride to stabilize the zirconium and yttrium. A method in which a sol of hydroxide is produced with a chemical agent, which is then filtered, washed, dried, and then heat-treated.

(Co-precipitation method) (2) A method in which a mixed aqueous solution similar to the above-mentioned coprecipitation method is heated to generate a sol of hydroxide, etc., followed by filtration, washing, drying, and subsequent heat treatment. (Hydrolysis method) (3) A zirconium alkoxide such as zirconium isopropoxide and a metal element alkoxide constituting a stabilizer such as yttrium isopropoxide,
A method of mixing and dissolving in an organic solvent, adding water to the solution to hydrolyze the alkoxide to produce a sol, followed by filtration, washing, drying, and subsequent heat treatment. (Alkoxide method) The ceramic raw material used in the present invention preferably has a soft particle size of 1 μm or less, and is preferably as fine as possible.

From this point of view, the method for preparing the above ceramic raw material is one in which the particles are fine and the particle size distribution is narrow.
A wet method is preferred since it provides a product with a uniform composition. Next, the ceramic raw material prepared in this way is used to produce a precursor for plastic working.

When a powder is used as a precursor, the ceramic raw material may be used as it is, but it is preferably used in the form of granules with a diameter of 100 to 200 μm, which have excellent fluidity.

The granules can be prepared by using a spray dryer or the like from a slurry of ceramic raw materials containing a water-soluble resin such as polyvinyl alcohol and hydroxyethyl cellulose.

When a powder compact is used as a precursor, a pressure molding method in which the above-mentioned granules are pressed, a casting molding method in which a slurry of ceramic raw material is poured into a mold made of gypsum, etc., and a plastic molding method consisting of an organic binder, aged ramic raw material, and water. An extrusion molding method in which the mixture is extruded through a die; a hydrostatic press molding method in which the ceramic raw material is filled as it is or granules are filled into a rubber mold and pressure is applied isotropically; Prepare a powder compact by selecting an appropriate method from known methods, such as injection molding by extruding into a mold, or sheet molding by forming a mixture of a resin binder and ceramic raw material into a thin film using a doctor blade, etc. ・Prepare a calcined compact When used as a precursor, the powder compact is heated to 600 ml at normal pressure.
A calcined molded product is prepared by heat treatment at a temperature of ~1200°C.

Heat treatment is usually carried out in an oxidizing atmosphere such as the air, an inert atmosphere such as a nitrogen atmosphere, or a vacuum atmosphere, but an oxidizing atmosphere in which the organic substances contained are removed by incineration is advantageous. The heat treatment is carried out using a commonly used high-temperature furnace such as an electric furnace, gas furnace, or heavy oil furnace. A normal sintered body is
After molding using an organic binder such as paraffin,
Because it is fired at a high temperature of about 1,500°C, it has a large plastic resistance, making cutting with a lathe extremely difficult. but,
In the case of the above-mentioned calcined product, it is easy to cut it with a lathe, so it is easy to cut the calcined product, shape it into an approximate shape, and then expand the necessary parts in the subsequent plastic processing. It has the advantage of being able to efficiently manufacture products with complex shapes. Furthermore, if a sintered compact is used as a precursor, the particles will grow in the subsequent plastic working step, making it easier to transition from tetragonal to monoclinic crystals and increasing the content of monoclinic crystals. If a calcined molded product or powder or powder molded product made of the ceramic raw material is used as a precursor, the grain growth will be small and the monoclinic crystal will increase due to the transition from tetragonal crystal to monoclinic crystal. is very small. It is thought that this phenomenon promotes the increase in strength due to plastic working.

The plastic working is preferably carried out under the conditions of temperature t (° C.) and pressure P (kg f /w”) expressed by the following formula.

P≧3X10-Tom'X(1600-t)I'+0.1P
≦5. t≦1600 Then, illustrating the range represented by this formula, the first
It will look like the figure.

If the thickness exceeds the above range (deviating from the range), the plastic working resistance will be extremely high, making it difficult to industrially obtain a dense sintered body, and requiring complicated operations and expensive and complicated equipment.Plasticity Processing is performed using jigs made of alumina, silicon carbide, carbon, etc. that utilize plastic deformation such as rolling, extrusion, drawing, and forging. For example, electrical heating, gas combustion heating, dielectric heating, etc. The test is carried out in the high temperature furnace used in various atmospheres such as an oxidizing atmosphere such as atmospheric air, an inert atmosphere such as nitrogen atmosphere, and a vacuum atmosphere by applying tensile force or compressive force using a hydraulic mechanism or the like.

The heating method, atmosphere, etc. may be appropriately selected from known methods.

(Effects of the Invention) The zirconia sintered compact of the present invention has a small porosity, is dense, and has high strength, and can be made of zirconia that is dense and has excellent dimensional accuracy in complex shapes or ultra-thin shapes without any post-processing. Sintered bodies can be easily obtained. Therefore, it is used for mechanical parts such as automobile engines that require complex shapes, gas sensors, fuel cells, oxygen pumps, etc. that require a reduction in electrical resistance by thinning the film. This solid electrolyte is suitable for use in cutlery such as scissors and knives, which are extremely thin and require dimensional accuracy.

The present invention will be specifically described below with reference to Examples.

In addition, in the examples, the average particle diameter, bending strength, and monoclinic crystal content were measured by the following methods.

(1) Break the average particle size sample, observe the broken surface with an electron microscope,
This is a value calculated from the average value of the measured particle diameters.

(2) Bending strength This is a value obtained by cutting the sample into 8 x 4 x 40 mm sample pieces, polishing the sample surface, and using a 4-point bending test method in accordance with JI8R1601.

(3) Specify the monoclinic content of the sample as X! Analysis was performed by a single diffraction method, and the content of monoclinic zirconium oxide was calculated based on the following formula from the integrated intensity obtained from the peak area of the diffraction pattern.

Here, M is monoclinic zirconium oxide (7) (111)
The sum of the integrated intensities of the (I IT) plane T is the integrated intensity of the (111) plane of tetragonal zirconium oxide C is the integrated intensity of the (111) plane of cubic zirconium oxide Put about 40f into a mold and heat it to 2.5 (kgf/mm2) at 20°C.
) and then calcined in an electric furnace. For calcining, the temperature was raised to 1100°C at a rate of 15°C/nl 1 n, held at 1100°C for 80 minutes, and then heated to 15°C.
Cooling was performed at a cooling rate of °C/m 1 H. The bending strength, grain size, monoclinic content, and porosity of the calcined molded product were each 4.
(kgf/mm”), 0.15”;;7t
9 mol% and 4196. Next, the calcined product was placed in a silicon carbide mold and heated at 20°C/min in an electric furnace up to 1200°C, and at 15° from 1200°C to the specified temperature listed in Table 1. After increasing the temperature at a rate of C/rn t n, the stress described in the same table was applied and pressure was applied from both sides. After 060 minutes of pressurization, rapid contraction occurred at the beginning of pressurization, densification progressed, and then plastic deformation gradually occurred.
The pressure was removed and the mixture was cooled at a cooling rate of 15°C/min. The results are shown in Table 1.

As is clear from Table 1 below, plastic working improved the strength of all materials, especially Bun No.
, 18, an improvement in strength was observed.

In Bun No. 18, a high strength change of about 80 times was observed. - Plastic deformation was noticeable at temperatures above 1800°C, causing lateral spread of the pressurized surface, resulting in the desired shape and Example 2 In Example 1, Same as Example 1 except that prescribed amounts of magnesium oxide, calcium oxide and cerium oxide listed in Table 2 below were used instead of yttrium oxide, and plastic working was performed under the plastic working temperature and pressure conditions listed in Table 2. A zirconia sintered body was produced. The results are shown in Table 2.

From Table 2, it was found that even when magnesium oxide, calcium oxide, and cerium oxide were used as stabilizers in place of yttrium oxide, they showed the same tendency as yttrium oxide.

Comparative Example 1 In Example I Run No. 18, the precursor was fired under normal pressure under the conditions shown in Table 8 below instead of under the pre-calcination conditions to form a so-called sintered product, and the other conditions were as in Example 1. A zirconia sintered body was produced in the same manner. The results are shown in Table 8. -5 Table 8 From the above table, when a sintered shaped product is used as a precursor, the particles grow in the subsequent plastic working process, and the transition from a tetragonal product to a monoclinic product is likely to occur, and the monoclinic content increases. However, when a calcined product is used as a precursor as in the present invention, grain growth is small and the monoclinic content decreases, contrary to the comparative example.

Example 8 Run No. of Example I except that a ceramic raw material having an average particle size of 1.8 μm was used in Example 1.

A zirconia sintered body was manufactured in the same manner as in 18.
In addition, in the above comparative example, an attempt was made to produce a zirconia sintered body in the same manner as in the above comparative example except that a ceramic raw material having an average particle size of 1.8 μm was used. The results are also shown in Table 4 below.

As shown in the upper table of Table 4, in the comparative example in which pressureless sintered material was used as a precursor, the plastic working resistance was extremely large and plastic working was impossible, but it was not possible to plastically work the pre-sintered material with the precursor. It is clear that the result is a significant improvement in strength.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the range of preferable conditions during plastic working in the present invention, where the horizontal axis represents temperature t (°C) and the vertical axis represents applied stress P (kg f/mm"). t('C)

Claims (4)

[Claims] (1) Zirconium oxide (A) and yttrium oxide,
A monoclinic calcined molded product, powder, or powder molded product made of a ceramic raw material containing at least one stabilizer (B) selected from the group of cerium oxide, calcium oxide, and magnesium oxide as a main component. A zirconia sintered body that is plastically processed by applying stress at high temperatures without increasing crystallization. (2) Zirconia according to claim (1), wherein the plastic working is performed under the conditions of temperature t (°C) and applied stress P (kgf/mm^2) shown by the following formula: Sintered shaped body. P≧3×10^-^3^7×(1600-t)^1^4
+0.1P≦5, t≦1600 (3) The zirconia sintered body according to claim (1) or (2), which contains at most 15 mol% of the stabilizer (B). (4) The zirconia sintered body according to any one of claims (1) to (3), wherein the ceramic raw material has an average particle diameter of 1 μm or less.