TW201439005A - Zirconium tungstate - Google Patents

Abstract

The invention of the present application provides zirconium tungstate which is characterized in that the intensity of a peak appearing in a range of 2[theta] = 23.5 to 23.9 not ranges from 92 to 115% when the intensity of a diffraction peak appearing in a range from 2[theta] = 21.4 to 21.8 not is 100% in X-ray diffraction. Conventionally, there is a problem that the synthesis of a crystal of zirconium tungstate takes a long time, and therefore the application of zirconium tungstate to products has not been advanced. It is reported that zirconium tungstate can be produced using a platinum crucible in a laboratory. However, this production technique is not suitable for the mass production of zirconium tungstate. There is also a problem that zirconium tungstate volatilizes easily (the weight of zirconium tungstate usually is reduced by 0.3% at 950 not C within 2 hours) and therefore it is difficult to control the chemical composition of zirconium tungstate. The invention of the present application addresses the problem of controlling the chemical composition of zirconium tungstate and improving the quality of zirconium tungstate to improve the yield of zirconium tungstate, and also addresses the problem of performing the synthesis of a crystal of zirconium tungstate within an extremely short time to reduce the cost required for the production of zirconium tungstate.

Description

Zirconium tungstate

The present invention relates to a material having a negative expansion coefficient (the volume becomes smaller as the temperature rises) used when adjusting the expansion coefficient of glass.

In recent years, precision mechanical parts, optical parts, and electronic material packages, which are increasingly required to be highly precise, must be protected against the occurrence of deformation accompanying temperature changes caused by the external environment. Further, depending on the type of sensor, in order to operate reliably in an emergency, it is required to avoid deterioration of the element due to such stress, and it is required to have a long-life material design.

The expansion deformation is caused by the difference in the volume change in the joint interface of different materials, and sometimes becomes an important cause of peeling or cracking.

As the temperature rises, the volume-contracted negative expansion material is combined with a material having a large portion of the material to exhibit positive thermal expansion, whereby the thermal expansion rate of the composite material can be controlled, and thus attention is being paid. In particular, zirconium tungstate (ZrW ₂ O ₈ ) has a large heat shrinkage coefficient and exhibits an isotropic negative thermal expansion in a wide temperature range. Further, the environmental limit has recently become strict, and since it is a non-lead-based material that does not use lead, it is a highly anticipated material.

However, since ZrW ₂ O ₈ reported negative thermal expansion in the 1960s, various studies have been conducted, but a method in which perovskites exhibit a high crystallization ratio and mass production has not been established.

In the prior art, Patent Document 1 listed below proposes a method for stably producing a large-sized and high-purity single-phase zirconium tungstate (ZrW ₂ O ₈ ). In the method of Document 1, first, a liquid phase method (sol-gel method) is used to prepare an amorphous powder in which the element of the target substance becomes a correct stoichiometric ratio, and then, it is energized by means of discharge plasma sintering or the like. Pressure sintering. It is preferable to prepare a seed crystal in advance by baking the amorphous powder at a normal temperature at a temperature of 500 ° C to 700 ° C, and subjecting the amorphous powder to electric current pressure sintering by a method such as discharge plasma sintering.

Further, it is proposed that a single-phase zirconium tungstate (ZrW ₂ O ₈ ) having more excellent crystallinity can be obtained by the above method. However, even in this method, it takes a long time to carry out the liquid phase reaction of the amorphous powder, and it is filled into a graphite mold (mold diameter 20 mm). ) and the batch processing of pressurization is carried out, so it is not suitable in terms of the true mass production (manufacturing line of several tons or more per month).

As another conventional technique, in Patent Document 2, an oxide (WO ₃ and ZrO ₂ ) is used as a starting material, and the raw material is set to a bipolarized particle size distribution, and the raw material powder is placed in the same manner. A manufacturing method for sintering in a mold to be used. However, in the sintering method of the oxide powder disclosed in Patent Document 2, it is necessary to mix for a long period of time and to sinter for a long period of time, and in fact, it is impossible to manufacture in a short time and cost a manufacturing cost.

Further, in Patent Document 3, a compound in which two metal elements are chemically bonded via oxygen (A ⁴⁺ M ₂ ⁶⁺ O _{8 ) is} proposed using zirconium oxychloride and a tungstate containing no Na ion as a starting material. The mixture was hydrolyzed in H ₂ O for 10 hours, refluxed with HCl for 48 hours, and the solid matter was filtered, and after aging for 7 days, it was baked at 600 ° C for 10 hours under normal pressure to prepare zirconium tungstate (ZrW ₂ O ₈ ). .

However, in the method of performing normal pressure sintering of the powder raw material prepared by the liquid phase method, the tungsten component is unstable, stable production cannot be performed, and the firing takes a long time, so that the mass productivity is poor.

Patent Document 1: Japanese Laid-Open Patent Publication No. 2006-44953

Patent Document 2: Japanese Laid-Open Patent Publication No. 2003-342075

Patent Document 3: U.S. Patent No. 6183713

As described above, there is a problem that the synthesis of crystallization takes a long time, and the application of the product has not progressed so far. Although there are reports of production using platinum rhodium at the laboratory level, it is not suitable for mass production. Further, the tungsten oxide has a problem that it is easily volatilized (the weight is reduced by 0.3% at 950 ° C to 2 h), and it is difficult to control the composition. The object of the present invention is to reduce the composition variation, improve the quality and productivity, and synthesize the crystallization into a very short time, thereby reducing the manufacturing cost.

In order to solve the above problems, the following inventions are provided.

1) A zirconium tungstate having a diffraction peak intensity at 2 θ = 23.5 to 23.9° when the intensity of a diffraction peak at 2 θ = 21.4 to 21.8° in the X-ray diffraction is set to 100% 92~115%.

2) The zirconium tungstate according to the above 1), wherein the half-peak width of the diffraction peak at 2 θ = 21.4 to 21.8° is 0.05° or more and 0.2° or less.

3) The zirconium tungstate according to the above 1) or 2), wherein the diffraction angle is 2 θ = 15 to 60°, and is located at the 2 θ position of the card number 00-050-1868 not registered in the JCPDS. The intensity of the diffraction peak is 2% or less when the peak intensity at 2 θ = 21.4 to 21.8° is 100%.

4) A method for producing zirconium tungstate using the following WO ₃ powder as a raw material, wherein the WO ₃ powder has a half-peak width of 0.25° or more, or 2 θ, of three diffraction peaks of 2 θ=22 to 24°, respectively. The peak of =33~37° is a single peak, or the peak of 2θ=49°~51° or 53°~57° is a single peak.

(5) The method for producing zirconium tungstate according to the above 4), wherein the WO ₃ powder and the ZrO ₂ powder are sufficiently mixed, and then held at 1190 ° C or higher for 30 seconds or more, and rapidly cooled to 200 ° C in 3 minutes. It is produced below.

Previously, the synthesis of crystallization took a long time, and so far, no application has been made to the product. Although there are reports of production using platinum rhodium at the laboratory level, it is not suitable for mass production. Further, the tungsten oxide is easily volatilized (the weight is reduced by 0.3% at 950 ° C to 2 h), and it is difficult to control the composition.

The invention of the present invention can solve such problems, can reduce variation in composition, improve quality and productivity, and can perform synthesis into crystallization in a relatively short period of time to achieve a significant effect of reducing manufacturing cost.

Figure 1 is a graph showing the results of XRD of WO ₃ powder.

Fig. 2 is a graph showing the results of XRD of a standard ZrO ₂ powder.

Fig. 3 is a view showing the results of XRD of Examples 1 to 3.

Fig. 4 is a graph showing the results of XRD of Examples 4 to 6.

Fig. 5 is a graph showing the results of XRD of Comparative Examples 1 and 2.

Fig. 6 is a graph showing the results of XRD of Comparative Examples 3 to 5.

The zirconium tungstate according to the present invention is characterized in that, when the diffraction peak intensity at 2 θ = 21.4 to 21.8° in the X-ray diffraction is set to 100%, the peak at 2 θ = 23.5 to 23.9 ° is 92~. 115%.

Four types of the following Table 1 are registered in the X-ray diffraction (JCPDS: Joint Committee for Powder Diffraction Standards). That is, there are four types of card numbers 00-013-0557, 00-050-1868, 01-083-1005, and 01-087-1528.

The diffraction peak intensity of either θ=21.552~21.690° is greater than 2 θ=23.643~ The diffraction peak intensity of 23.789°.

On the other hand, in the invention of the present invention, the diffraction peak of the latter is larger than the conventional relative intensity ratio, and there is no prior "zirconium tungstate" which exhibits the feature.

By utilizing this feature, zirconium tungstate can be effectively utilized as shown below. The thermal expansion coefficient of the zirconium tungstate of the present invention was measured by TMA (thermomechanical analysis) to be -9.6 × 10 ^-6 /K, showing a large negative thermal expansion property equivalent to or higher than the conventional one. Since the zirconium tungstate has a very large negative expansion coefficient, it can be more effectively produced into a zero-expansion material having an expansion ratio infinitely close to zero by being added to the positive expansion material which becomes the main body.

Further, in the element which is joined by different materials, it is possible to suppress the occurrence of the expansion deformation by adding a negative expansion material to increase the expansion coefficients of the two materials, and in this case, it is also possible to It is very effective because it achieves the same effect as the addition amount of the same amount or less.

Further, in the production of the zirconium tungstate of the present invention, unlike the standard crystal structure of WO ₃ (card number 01-083-0950), the half width of three diffraction peaks of 2 θ = 22 to 24 ° is obtained. The diffraction peaks of 0.25° or more or 2 θ=33 to 37° are substantially integrated and single, or the peaks of 2θ=49° to 51° or 53° to 57° become flat crystallization. The WO ₃ powder (Fig. 1.a) in an insufficient state is mixed and pulverized with a standard ZrO ₂ powder (Fig. 2), and a raw material before heating synthesis having an average particle diameter of 2 μm or less is prepared.

The WO ₃ powder in a state in which the above crystallization is insufficient can be determined (evaluated) by the diffraction peak. That is, the half-peak width of the diffraction peak is 0.25° or more, or the diffraction peak of 2θ=33-37° is substantially integrated and single, or a peak of 2θ=49°~51° or 53°~57°. The flat form is a WO ₃ powder in a state in which crystallization is insufficient.

Further, after being crystallized to zirconium tungstate (ZrW ₂ O ₈ ) at a high temperature of 1190 ° C or higher for 30 seconds or more, it can be achieved by instantaneous cooling in order to avoid decomposition into WO ₃ or ZrO ₂ again at the time of cooling. The cooling rate at this time is preferably within 3 minutes, more preferably within 200 minutes or less within 1 minute.

The "zirconium tungstate" of the present invention described above can be converted into a material having a crystal structure of zirconium tungstate in a very short time when heated, so that the volatilization of WO ₃ having a high vapor pressure can be suppressed and reduced. Changes in composition can improve quality and productivity. Moreover, the short-time synthesis can also achieve mass production or reduction.

Further, the zirconium tungstate according to the present invention has the following characteristics: the half-peak width of the X-ray diffraction peak at 2 θ = 21.4 to 21.8° is 0.05° or more and 0.2° or less, and is located in the card 00-050 not registered in JCPDS. The intensity of the diffraction peak at the θ position of -1868 is 2% or less when the peak intensity at 2 θ = 21.4 to 21.8° is 100%.

Example

The invention of the present invention will be described based on examples and comparative examples. Furthermore, this embodiment is merely an example and is not limited to this example. That is, other aspects or modifications included in the present invention are included.

(Example 1-3)

WO ₃ powder (Fig. 1.a) which does not have a complete WO ₃ crystal structure as an intermediate product when reduced from APT (ammonium paratungstate) to metal tungsten, and which is not stabilized by addition of Ca or Y or the like The pure ZrO ₂ powder was weighed in such a manner that the molar ratio was 2:1, and mixed by a pulverizer and finely pulverized to an average particle diameter of 0.3 μm.

The raw material was placed in a container with a platinum foil attached to the inside of the quartz crucible, and kept at 1200 ° C for 10 hours in the atmosphere (Example 1), 1 hour (Example 2), and 10 minutes (implementation) After the example 3), the crucible was taken out while maintaining the furnace temperature at 1200 ° C, and the crucible was quickly turned over to introduce the raw material into water having a sufficient water content of 20 ° C. The results of the X-ray diffraction obtained under this condition are shown in Fig. 3.

Further, the value of 2 θ and its half-peak width which are located at 2 θ=21.4 to 21.8° and the peak of the diffraction peak intensity ratio is set to 100, and the other main peak of zirconium tungstate is located at 2 θ=23.5. The specific 2 θ of the diffraction peak of ~23.9° and its intensity ratio, and further in the range of 2 θ=15~60°, are located at the diffraction peaks of the 2 θ position not registered in the JCPDS card 00-050-1868. The values of the peak comparisons at 2 θ = 21.4 to 21.8 are shown in Table 2.

Examples 1 to 3 are zirconium tungstate having high purity, and the strength ratio is 102%, 106%, and 115% which are not present in the conventional JCPDS card. There is a possibility that since WO ₃ as a raw material is an unstable crystal structure, it is rapidly progressed before crystallization of zirconium tungstate as compared with a material having a complete crystal structure of WO ₃ . Further, it is considered that the rapid cooling from 1200 ° C is sufficient, and the temperature can be lowered without significantly changing the crystal structure formed at a high temperature. Further, since the half-peak width of the diffraction peak at 2 θ = 21.4 to 21.8° is narrower than 0.05° and not more than 0.2°, it is also known that the crystallinity is high.

(Examples 4-6)

The mixed raw materials of WO ₃ and ZrO ₂ prepared in the same manner as in Example 1-3 were placed in a crucible, heated in a continuous furnace (rotary oven) at 1200 ° C for 1 hour in the atmosphere, and then introduced into a cooling zone. The bath of liquid nitrogen is rapidly cooled.

Example 4-6 is a material located above the crucible (Example 4), a material on the side of the crucible (Example 5), and a material located inside (Example 6). The X-ray diffraction results are shown in Fig. 4, and the peak analysis results are shown in Table 2.

Examples 4 to 6 are zirconium tungstate having high purity, and the X-ray diffraction intensity ratio is 94%, 95%, and 92% which are not present in the conventional JCPDS card.

The reason why the strength ratio is lowered as compared with Examples 1 to 3 may be affected by a slightly slower cooling rate due to the heat capacity than when it is introduced into water, but zirconium tungstate having an unprecedented crystallinity can be obtained. .

(Comparative Example 1)

Having sufficient of WO WO ₃ powder (FIG. 1.B) was mixed with ZrO ₂ powder used in Examples 1 to 6 of the embodiment pulverized, to put the inside of the quartz crucible ₃ crystal structure is affixed to the container of the platinum foil, The mixture was heat-treated at 1200 ° C for 10 hours in the air, and was introduced into water in the same manner as in Examples 1 to 3. The X-ray diffraction results are shown in Fig. 5. The crystal structure of zirconium tungstate cannot be obtained.

(Comparative Example 2)

The raw material production and heating were carried out under the same conditions as in Example 1. The cooling only method was carried out by taking 8 hours to return to room temperature. The X-ray diffraction results of the obtained material are shown in Fig. 5. The crystal structure of zirconium tungstate cannot be obtained.

(Comparative Example 3)

The raw materials were prepared in the same manner as in the examples 1 to 3, and the heat treatment was carried out under the conditions of a temperature increase rate of 1200 ° C for 8 hours and a holding time of 1200 ° C of 60 hours, and the same as in the first to third embodiments. Cool down to the water. The X-ray diffraction results of the obtained material are shown in Fig. 6. Further, the analysis results of the peaks are shown in Table 2.

Although the crystal structure was mainly shown to be zirconium tungstate, a peak different from ZrW ₂ O ₈ appeared in the vicinity of 2 θ = 21.3 °, and the intensity ratio was 29%. It is considered to be a phase rich in ZrO ₂ due to evaporation of WO ₃ in the heat treatment.

(Comparative Example 4-5)

Considering the volatilization of WO ₃ in the heat treatment, the WO ₃ and ZrO ₂ powders were mixed and pulverized in a molar ratio of 2.1:1, and placed in a container with a platinum foil attached to the inside of the quartz crucible in the atmosphere. The mixture was heat-treated at 1200 ° C for 1 hour (Comparative Example 4) and 30 hours (Comparative Example 5), and was placed in water in the same manner as in Examples 1 to 3. The X-ray diffraction results of the obtained materials are shown in Fig. 6, and the results of analysis of the peaks thereof are shown in Table 2.

Although the crystal structure was mainly shown to be zirconium tungstate, a peak different from ZrW ₂ O ₈ appeared before 2 θ = 23.7 °, and the intensity ratio was 37% and 7%. It is a peak associated with WO ₃ and is believed to be excessively more than evaporation due to WO ₃ .

In the case of heat treatment for a long period of time, evaporation of WO ₃ must be considered, and it is difficult to obtain stable quality. On the other hand, when crystallization is performed in a very short time as in the embodiment, there is a feature that the target composition can be stably produced.

[Industry use possibility]

As is conventionally known, there is a problem that the synthesis of crystallization takes a long time, and the application of the product has not progressed so far. Although there are reports of production using platinum rhodium at the laboratory level, it is not suitable for mass production. Further, the tungsten oxide is easily volatilized (the weight is reduced by 0.3% at 950 ° C to 2 h), and it is difficult to control the composition. The present invention provides a zirconium tungstate which is a diffraction peak intensity at 2 θ=23.5 to 23.9° when the intensity of a diffraction peak at 2 θ=21.4 to 21.8° in the X-ray diffraction is set to 100%. It is 92~115%.

Thereby, the yield can be improved by reducing the composition variation and improving the quality, and the synthesis into crystallization can be performed in a relatively short time, thereby reducing the manufacturing cost. In this way, it is possible to provide a material having a negative expansion coefficient (the volume becomes smaller as the temperature rises), and thus it is possible to contribute greatly to an industry used for adjusting the expansion coefficient such as glass.

Claims (5)

A zirconium tungstate having a diffraction peak intensity of 2 θ=23.5 to 23.9° when the intensity of the diffraction peak at 2 θ=21.4 to 21.8° is set to 100% in the X-ray diffraction. 115%. The zirconium tungstate according to the first aspect of the patent application, wherein the half-peak width of the diffraction peak at 2 θ = 21.4 to 21.8° is 0.05° or more and 0.2° or less. Zirconium tungstate according to claim 1 or 2, wherein the diffraction angle is 2 θ=15 to 60°, and is located at the 2 θ position of the card number 00-050-1868 not registered in JCPDS. The intensity of the peak is 2% or less when the peak intensity at 2 θ = 21.4 to 21.8° is 100%. A method for producing zirconium tungstate using the following WO ₃ powder as a raw material, wherein the half-peak widths of the three diffraction peaks of the WO ₃ powder at 2 θ=22 to 24° are respectively 0.25° or more, or 2θ=33 The peak of ~37° is a single peak, or the peak of 2θ=49°~51° or 53°~57° is a single peak. The method for producing zirconium tungstate according to the fourth aspect of the invention, wherein the WO ₃ powder and the ZrO ₂ powder are mixed, and maintained at 1190 ° C or higher for 30 seconds or more, and rapidly cooled to 200 ° C or less in 3 minutes. And making it.