JPH0238353A - Calcined heat-resistant phosphate compound compact and production thereof - Google Patents

Abstract

PURPOSE:To suppress a weight loss due to evaporation of phosphorus by blending oxides of Zr, P and Si with a salt of a specific element, calcining the resultant blend and providing a specified crystal phase. CONSTITUTION:A substance selected from ZrP2O7, (ZrO2)2P2O7, ZrO2, ZrSiO4, SiO2 and phosphates and silicates of R (R is element capable of providing di- to trivalent ions) and RO is used as raw materials. The above-mentioned raw materials are blended at a ratio so as to provide RyZr4SixP6-xO24 (R is one or more elements capable of providing di- to trivalent ions; x is a number of <=0 to <6; y is a number of >=2/3 to (4 satisfying electrical neutral conditions expressed by the formula) to afford a batch mixture, which is then formed into a compact. The resultant compact is subsequently calcined at about 1400-1800 deg.C for 2-10hr to provide a calcined compact containing 10wt.% crystal phase expressed by the afore-mentioned formula. The weight loss of the calcined compact is <=10% by heat treatment at 1400 deg.C for 100hr.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a heat-resistant phosphate compound sintered body and a method for producing the same, and more specifically, to a heat-resistant sintered body of a phosphate compound and a method for producing the same. The present invention relates to an excellent sintered phosphate compound and a method for producing the same.

[Prior Art] In recent years, with the progress of industrial technology, there has been an increasing demand for materials with excellent heat resistance and low expansion properties.

In response to these demands, zirconyl phosphate ((ZrO)2
P20? ) has been found to be promising as a material with excellent heat resistance and low expansion properties.

Furthermore, recently, zirconium phosphate of an alkali metal such as sodium has been proposed as a material having heat resistance and a low coefficient of thermal expansion. (Mat, Res.

Bull, Vol. 19. pp, 1451-14
56 (1984), Journal of Materi
als 5science 16, 16:13-1642
(1981), and Ceramics Association Journal 95 [5], No. 53
1-537 (1987)) Furthermore, alkaline earth metal phosphate compounds of a specific composition have also been proposed as having low expansion properties. (Mat, Res,
Bull, Vol, 20°pp, 99-106.
1985, and J. Am. Ceram, Soc., 7
0 [10IC-232~G-2:16 (1987))
Also, in US Pat. No. 4,675,302.

(:ao, A ceramic material having the basic composition of 5TizP+0+z has been proposed as having excellent low expansion properties.

[Problems to be Solved by the Invention] However, although phosphate compounds such as the above-mentioned zirconyl phosphate have the advantage of being excellent in low expansion, there are problems common to these phosphate compounds.
At high temperatures above 00°C, thermal decomposition occurs and phosphorus (
P) evaporation. For example, 14
There is a problem in that when heat treated at 00'C for 100 hours, zirconyl phosphate shows a weight loss of as much as 19%.

Furthermore, the ceramic material proposed in U.S. Pat. No. 4,675,302 is mainly used for the substrate of a low-expansion optical reflector that does not undergo deformation due to temperature changes for artificial satellites. As shown in FIG. 2, the temperature change is intended to be at most about 500°C, and no consideration is given to stability, heat resistance, etc. at high temperatures of, for example, 1200°C or higher.

On the other hand, methods for producing phosphate compounds include Na2Co,
, ZrO□, Zr0C1248zO, 5in2, (
NI+, )2HP04, H:+PO< , Nb1Os
, YzOi, SrCO3, K2CO2, CaC0,
.

A method using a combination of the following is known. (T.

0ota and 1. Yamai, Journal
of the Atner'rcan Ceramic
5ociety, 69. (1986)) However, in the above production method, p2o is produced during the decomposition of ammonium phosphate or 83PO.

The components are produced independently, forming areas with a locally high phosphorus concentration, resulting in the production of low-melting compounds during sintering.

For this reason, large bores (voids) are formed in the sintered body mainly in the low melting point compound, resulting in serious defects.

[Means for Solving the Problem] Therefore, in order to solve the problems of the above-mentioned conventional technology, the present inventor conducted various studies, and found that a certain kind of additive was found to suppress weight loss due to evaporation of phosphorus. It is effective to add an agent and sinter it, in which case the sintered body will have the following properties:
It was discovered that a predetermined crystalline phase was formed, leading to the present invention.

According to the present invention, RyZr4SIxP6-xO
24 (R is selected from one or more elements that can be di- or trivalent ions, X is a value of 0 or more and less than 6, and y is a value of 2/3 or more and less than 4 that satisfies the electrical neutrality condition of the chemical formula)
A heat-resistant phosphate compound sintered body containing 10% by weight or more of a crystalline phase as a composition and having a weight loss rate of 10% or less when heat-treated at 1400°C for 100 hours, and ZrP2
O7, (lrO)zPzOt, ZrO2, Zr5iO
<, 5if2. Heat-resistant phosphate compound sintering, which consists of molding and firing a batch mixture consisting of a substance selected from H phosphate, H silicate, and RO (R is an element that can be a divalent or trivalent ion) A method of manufacturing a body is provided.

In the sintered body of the phosphate compound of the present invention, the general formula is Zr45ixp6-Xo as a crystal phase in the sintered body.
It is necessary to include those represented by □. Depending on the presence or absence of this crystal phase, the thermal stability at high temperatures differs greatly, as shown in the following explanation.

In addition, R is one or more elements that can become di- or trivalent ions, and generally represents an element belonging to the Ua group of the periodic table,
Preferably, it is composed of one or more of barium (Ba), strontium (Sr), and calcium (Ca).

Furthermore, according to the sintered body of the present invention, the weight loss rate due to phosphorus evaporation after heat treatment at 1400°C for 100 hours is as low as 10% or less when the open porosity is in the range of 50% or less. Moreover, the bending strength can be increased to 100
kg/cm2 or more. In other words, when the open porosity exceeds 50%, the bending strength decreases to 100 kg/c.
m", which means that the required strength when using ceramics as a practical material is not satisfied. Also, this sintered body has a strength of 140
The self-weight softening rate after heat treatment at 0°C for 5 hours is 0.3% or less, which satisfies the requirements as a heat-resistant material.

In addition, this sintered body has a small dimensional change rate and a temperature of 1400°
When heat treated at C for 100 hours, the dimensional change rate is 1
% or less, which also satisfies the requirements for a heat-resistant material. Furthermore, the coefficient of thermal expansion of this sintered body from room temperature to 1400°C is as low as 25X 10-'/"C or less, and it has excellent thermal shock resistance. Therefore, this sintered body has excellent thermal shock resistance. The sintered body of the invention is suitable for use in heat-resistant materials such as ceramic honeycomb structures such as automobile exhaust gas purification catalyst carriers, rotary heat storage type ceramic heat exchangers, heat transfer type heat exchangers, housings for turbocharger rotors, and engine manifold insulation materials. It is suitably applied to materials that require high properties and thermal stability at high temperatures.

Next, in the method for producing a heat-resistant phosphate compound sintered body according to the present invention, the raw materials are ZrP 207 , (Z
rO)2P207. ZrO2, ZrSiO4,5io
2. R phosphate, H silicate, and RO (R is 2-
It is characterized in that it is a batch mixture of powders made of substances selected from elements (elements that can form trivalent ions). That is, Zr
P2O7, (ZrO)2P207. ZrO2, ZrSi
O4, Sin, R phosphate, R silicate, and R
Each O is a stable compound, hardly causing non-uniformity during the forming and firing process, and can be fired at high temperatures, making it possible to obtain ceramics with excellent heat resistance.

On the other hand, when phosphoric acid, which is conventionally used, is used as a P2O5 source, since phosphoric acid is a liquid, it becomes non-uniform during the mixing process, and as mentioned above, locally high phosphorus concentration areas are formed, resulting in low yields a compound with a melting point. For this reason, a serious defect occurs in that a huge bore is formed in the sintered body mainly in the low melting point compound. In addition, when obtaining a honeycomb structure by extrusion molding clay containing phosphoric acid, the corrosive nature of phosphoric acid can cause the extrusion die and cylinder of the extrusion molding machine to rust or corrode, resulting in significant molding failure. It becomes difficult. Furthermore, when applied to press molding, there is a drawback that molding as a powder is impossible due to the phosphoric acid content due to the wood quality.

Also ZrP2O7, (ZrO)2P207. ZrO,
, ZrSiO4, sio, R phosphate, R silicate and RO usually contain 0-84.2% by weight of ZrP2O7, 0-82.3% by weight of (ZrO)zP207,
2 is 0 to 51.7% by weight, ZrSiO4 is 0 to 77.2% by weight.
Weight%, SiO□ is 0-37.8% by weight, R phosphate is 0-44.6% by weight, R silicate is 0-53.0% by weight, Ro is 0-42.1% by weight. %, but among these, ZrP2O7, (ZrO)2P207, R phosphate Noy, and RO, H silicate or R phosphate must be included in the batch mixture. It is necessary.

Further, as the raw material component RO, it is also possible to select and use Ro1, that is, stable compounds such as hydroxides, carbonates, and sulfates that convert into oxides during firing.

Note that the average particle diameter of the raw material used is usually 50 JLm or less, preferably 10 JLm or less.

As the firing conditions for the sintered body of the present invention, the firing temperature is 1400°C.
The firing time is 1 to 24 hours, preferably 2 to 10 hours.

By setting the firing temperature to 1400°C or higher, it is possible to obtain the phosphate compound sintered body of the present invention containing 10% by weight or more of RyZr4SixPg-U0□4 as a crystal phase.

Furthermore, if the firing time is less than 1 hour, the sintering is insufficient, and if it exceeds 24 hours, the strength will be lowered due to abnormal grain growth, and a different phase will be precipitated due to evaporation of phosphorus.

The preferred embodiments of the present invention explained above are summarized as follows.

(a) A sintered phosphate compound composed of one or more of R, Ba, Sr, and Ca.

(b) Open porosity is 50% or less, bending strength is 100 kg/
A sintered body of a phosphate compound of C112 or higher.

(c) A sintered body of a phosphate compound having a softening rate under its own weight of 0.3z or less after heat treatment at 1400°C for 5 hours.

(d) A sintered body of a phosphate compound having a dimensional change rate of 1% or less when heat treated at 1400°C for 100 hours.

(e) Thermal expansion coefficient from room temperature to 1400℃ is 25×1
A phosphate compound sintered body having a temperature of 0-7/'C or less.

(f) A sintered phosphate compound used as a ceramic honeycomb structure.

(g) A method for producing a sintered phosphate compound composed of one or more of R, Ba, Sr, (:a).

(h) A method for producing a sintered body of a phosphate compound selected from hydroxides, carbonates, and sulfates, in which RO is converted to RO during firing.

(i) Firing temperature is 1400°C or higher, firing time is 1 to 2
A method for producing a phosphate compound sintered body, which takes 4 hours.

[Examples] The present invention will be explained below based on Examples, but it will be clear that the present invention is not limited to these Examples.

(Example, Comparative Example) Zirconyl phosphate ((ZrO)2hOy), ZrP whose particle size was adjusted in advance according to the formulation ratio listed in Table 1
2O7, calcium carbonate, strontium carbonate, barium carbonate, yttoria, zircon, sodium carbonate, ceria, titania, silica, calcium phosphate, and zirconia were mixed. To adjust the particle size of zirconyl phosphate, a vibrating mill filled with Zr0z sintered cobblestones having a diameter of 5 mm was used, or a bot mill or an attritor can also be used. The ZrO□ sintered cobblestones used were those stabilized with MgO and those stabilized with Y2O3. The chemical composition of the boulders used is shown in Table 2. Further, chemical analysis values of the raw materials used are shown in Table 3.

10% PV in 100 parts by weight of the mixture of formulations shown in Table 1.
Add 5 parts by weight of aqueous solution A and mix thoroughly.

100 kg/ in 25X aox 6 mm mold
After press molding at a pressure of c+s'', rubber pressing was performed at a pressure of 2 tons/cs'' and dried. After drying, this molded body was fired in an electric furnace in the atmosphere under the conditions shown in Table 1.

The temperature increase rate was 5~b. The compact was processed into a 3 x 4 x 40 nm bending test piece as shown in JIS R1601 (1981), and
Weight loss and dimensional change rate during heat treatment for 1100 hours, thermal expansion coefficient from 40 to 1400°C, 4-point bending strength, self-weight softening, open porosity, and melting point were measured. used a push rod differential thermal dilatometer using a high-purity alumina sintered body.The measurement temperature range was 40 to 1400℃.
It is ℃. Four-point bending strength was measured according to the method shown in JIS R1601. The self-weight softening rate is 3x4x40mm between the supports with a width of 30mm shown in Figure 6.
A bending test piece was placed and heat treated in the atmosphere at 1400°C for 5 hours, and the deformation amount ΔX due to its own weight was measured using the following formula.

Self-weight softening rate=△X/textX100 (%) The open porosity was measured by the Archimedes method. The melting point is 3
A sintered body cut into a shape of x 4 x 5 mm was heat-treated in an electric furnace at 1650°C for 10 minutes, and whether or not it melted was visually judged. In addition, the amount of crystal phase of the sintered body is zirconyl phosphate (β-(ZrO)zhot) (C
communications of the Americas
(200) surface reflection peak value, R of ican Ceramic 5ociety, (Nie 80 (1984)).

(113) plane reflection peak value of Zr4P6-+cSjx02 [The index of the above composition crystal phase is J CP D S 33
-321. CaZr, (PO.

)6, J CP D S 33-1360.5rZr,
(PO4) s, JCPDS 34-95, Ba2r,
Indexed according to (PO,)6.

], Zircon JCP D S 6-266 (:1
12) Surface reflection peak value and JCPD of m-ZrO2
Quantification was performed using the (011) surface reflection peak value of S:14-95. However, since the relative intensity of the (011) plane reflection of m-ZrO2 is as low as 18/100, a value multiplied by 5.6 was used as the peak value. Regarding other different crystal phases, only their presence or absence was identified by X-ray diffraction patterns.

As is clear from the results of Examples 1 to 18 and Comparative Examples 19 to 27 shown in Table 1, RyZr<Pa-X
When containing 10% by weight or more of 5i, o□4 (R is one or more elements that can be divalent or trivalent ions), the weight when heat treated in the air at 1400°C for 100 hours, which is the objective of the present invention. A phosphate compound sintered body with a reduction rate of 10% or less was obtained. Moreover, such a sintered body is ZrP2O,
(ZrO) 2P20. y, zrO□, ZrSiO4,
It was obtained when a mixture consisting of a substance selected from 5iOz, R phosphate, H silicate and RO was sintered under the firing conditions shown in Table 1. Figure 1 shows the relationship between the weight loss rate when various oxides are added to the phosphate compound, and Figure 2 shows the relationship between the weight loss rate when various oxides are added to the phosphate compound.
a-11Si, 02. The relationship between the weight percent of the phase and the weight loss rate of the sintered body is shown. Figure 3 shows RyZr4Pa-+cSjxO! contained in the phosphate compound sintered body. 4 shows the relationship between the weight percent of the crystalline phase and the dimensional change rate of the sintered body.

From the above, RyZr4 in the phosphate compound sintered body
P6-xsi, 02< By containing 10% by weight or more of a crystal phase, a phosphate with excellent heat resistance and low weight loss rate and dimensional change rate when heat treated in the air at 1400°C for 100 hours. It can be seen that a compound sintered body can be obtained.

Incidentally, FIG. 4 is a graph showing the relationship between open porosity and bending strength of a sintered body of a phosphate compound.

Further, FIG. 5 shows an X-ray diffraction pattern of the phosphoric acid compound sintered body of Example 3. From this figure, as the crystalline phase (ZrO)
It can be seen that it contains 2P 207 and CaZr4(PO<)a.

[Effects of the Invention] As explained above, according to the heat-resistant phosphate compound sintered body of the present invention and its manufacturing method, RyZr, P6□Si,
By including 10% by weight or more of the crystal phase of 0□, (R is one or more elements that can become di- or trivalent ions),
The weight loss rate when heat treated at 400℃ for 100 hours is 1
It is possible to obtain a heat-resistant phosphate compound sintered body having a heat resistance of 0% or less.

Therefore, this phosphate compound sintered body is required to have heat resistance, low expansion property, and high temperature stability.For example, when formed into a honeycomb structure by extrusion molding, etc. It can be widely applied to ceramic turbocharger rotor housings or heat insulating materials in engine manifolds molded by slurry casting, press molding, injection molding, etc.

[Brief explanation of the drawing]

Figure 1 is a graph showing the weight loss rate during heat treatment at 1400°C for 100 hours when various oxides are added to the phosphate compound sintered body, and Figure 2 is a graph showing the weight loss rate of RyZ in the phosphate compound sintered body.
r4Pa-wsi, 1ot4 crystal phase amount and 1400℃, 1
A graph showing the weight loss rate during heat treatment for 00 hours, Figure 3 shows R, Zr, Pa-, Si,...
0□4 A graph showing the amount of crystalline phase and the dimensional change rate during heat treatment at 1400°C for 1100 hours. Figure 4 is a graph showing the relationship between open porosity and bending strength of sintered phosphate compounds. Figure 5 is a graph showing the relationship between the open porosity and bending strength of sintered phosphate compounds. A graph showing the X-ray diffraction pattern of the phosphoric acid compound of Example 3,
FIG. 6 is a diagram showing a method for measuring the softening rate under self-weight. Ozu R, Mi S! zP6-2024 m! ! ('10)R,
Zr45ixP6-x02. t t('10) Figure 4 V Rishi Prayer ("10)

Claims (2)

[Claims] (1) R_yZr_4Si_xP_6_-_xO_2_
4 (R is selected from one or more elements that can be di- or trivalent ions, x is a value of 0 or more and less than 6, and y is a value of 2/3 or more and less than 4 that satisfies the electrical neutrality condition of the chemical formula) Contains 10% by weight or more of crystalline phase, which is the composition, and has a temperature of 1 at 1400℃
A heat-resistant sintered phosphate compound having a weight loss rate of 10% or less when heat treated for 00 hours. (2) ZrP_2O_7, (ZrO)_2P_2O_7
, ZrO_2, ZrSiO_4, SiO_2, R phosphate, R silicate, and RO (R is an element that can be a divalent or trivalent ion). A method for producing a heat-resistant sintered phosphate compound, the method comprising obtaining an acid salt compound.