JP2002104877A - Method of synthesizing heat-shrinkable oxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To synthesize a lot of heat-shrinkable oxide such as Zr(1-x)HfxW2O8, Zr(1-x)YxW2O8 having a negative coefficient of thermal expansion with a low price. SOLUTION: The heat-shrinkable oxide is synthesized as follows: in a 1st process, a mixture of either one between zirconium oxide ZrO2 and hafnium oxide HfO2 or both of them is mixed with tungsten trioxide WO3 with mole ratio 1:2 of stoichiometric ratio, then refine them to obtain raw material powder; in a 2nd process, the powder is formed by pressing into a pellet; in a 3rd process the pellet is covered with platinum foil, or put into a quartz container, and sealed with platinum foil; in a 4th process, it is subjected to heat treatment in the atmosphere at the temperature of >=1160 deg.C to <=1250 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to the, _Zr has a negative thermal expansion coefficient _{(1-x) Hf x W} 2 O 8, Zr (1 -x)
The present invention relates to a method for synthesizing a heat-shrinkable oxide for synthesizing Y _x W ₂ O ₈ .

[0002]

_2. Description of the Related Art A heat-shrinkable oxide such as ZrW ₂ O ₈ having a negative coefficient of thermal expansion cancels out the influence of a shape change due to a temperature change of an element or the like for which thermal expansion control is a problem. Recently, applications are expected.

As this synthesis method, a solution method and a solid phase reaction method are known. Solution method may be by the following procedures [1] to [7], to synthesize a single phase polycrystalline body of the heat-shrinkable oxide ZrW ₂ O _8. [1]: including Zr of 0.5 mol ZrOCl ₂ · 8H
Aqueous solution A of ₂ O and (NH ₄ ) ₆ H containing 1 mol of W
Aqueous solution B of ₂ W ₁₂ O ₄₀ is prepared [2]: Aqueous solutions A and B are added dropwise to 25 ml of water while stirring, and 50 ml is added [3]: White precipitate formed is continuously stirred for 10 hours [ 4]: After adding 125 ml of 6 mol of HCl, 4
Reflux for 8 hours [5]: Cool to room temperature, decant and filter [6]: Leave the obtained solid for 7 days [7]: Heat treat in air at 600 ° C

[0004] The solid-state reaction method includes the following [1] to
According to the procedure [5], a single-phase polycrystal of the heat-shrinkable oxide ZrW ₂ O ₈ can be synthesized. [1]: ZrO ₂ and WO ₃ powders are mixed at a stoichiometric composition [2]: Vacuum sealing in a silica tube [3]: Heat treatment at 1150 ° C. for 12 hours [4]: Pulverization of the obtained white powder [5] : Heat treatment in a platinum crucible at 1200 ° C for 12 hours

[0005]

By the way, in order to apply the heat-shrinkable oxide as a thermal expansion control material, it is necessary to synthesize a large amount and at a low cost. However, the solution method described above, the raw material ZrOCl ₂ · 8H ₂ O and the (N
There is a problem that the stability of H ₄ ) ₆ H ₂ W ₁₂ O ₄₀ in air is poor, so that it is difficult to use. In addition, the solid-phase reaction method requires a large-scale facility for vacuum sealing in a silica tube, and there is a problem that the sealing operation is troublesome. Furthermore, in the above-mentioned synthesis methods, all can synthesize only a small amount of the heat-shrinkable oxide ZrW ₂ O _{8 of} less than 1 g at a time, and cannot meet a demand for mass synthesis.

Accordingly, an object of the present invention is to make it possible to synthesize a heat-shrinkable oxide in a large amount at low cost.

[0007]

[MEANS FOR SOLVING THE PROBLEMS]
In addition, the invention of claim 1 provides a Zr having a negative coefficient of thermal expansion.
_(1-x)Hf_xW₂O₈Heat for synthesizing (0 ≦ x ≦ 1)
A method for synthesizing a shrinkable oxide, comprising: a zirconium oxide Z
rO₂And hafnium oxide HfO₂Either one or
Both mixtures and tungsten trioxide WO₃And the molar ratio
Raw material powder mixed at a stoichiometric ratio of 1: 2 into pellets
Press molding, wrap this pellet in platinum foil, or stone
After putting in a British container and sealing with platinum foil,
The heat treatment is performed at a temperature lower than 250 ° C.

According to the present invention, for example, when synthesizing ZrW ₂ O ₈ , a mixture of zirconium oxide ZrO ₂ and tungsten trioxide WO ₃ at a stoichiometric ratio of 1: 2 by mole is used as a raw material powder. Therefore, zirconium oxide ZrO ₂ and tungsten trioxide WO ₃ do not remain as impurities when all of the raw materials react.

Further, since the raw material powder is formed into pellets, it is hardly deteriorated even if it is stored as it is, the handling is extremely simple, and if a certain number of pellets are heat-treated, the weight is weighed. And synthesis can be performed under the same conditions.

Since the pellets are wrapped in platinum foil or placed in a quartz container and sealed with platinum foil and heat-treated, even if heat-treated in air, tungsten W
Does not evaporate. Also, wrap the raw materials with platinum foil,
Alternatively, if it is put in a quartz container and sealed with platinum foil, it has been confirmed that even if heat treatment is performed in the air, impurities are not purified, and thus heat treatment is extremely simple.
Then, it succeeded in the synthesis of the heat-shrinkable oxide of at least about 4~25g by the process _ZrW 2 _{O 8.}

The raw material zirconium oxide ZrO ₂
In the case where hafnium oxide HfO ₂ or a mixture of zirconium oxide ZrO ₂ and hafnium oxide HfO ₂ is used instead of these, if these are mixed with tungsten trioxide WO ₃ in a stoichiometric ratio of 1: 2, Heat shrinkable oxide Z
rW ₂ part or all of the zirconium Zr in O ₈ was replaced with hafnium _{Hf Zr (1-x) Hf} x W 2 O 8 is synthesized.

The invention according to claim 2 is characterized in that zirconium oxide Zr
A raw material powder obtained by mixing a mixture of O ₂ and a trace amount of yttrium oxide Y ₂ O ₃ with tungsten trioxide WO ₃ at a stoichiometric ratio of 1: 2 is press-formed into pellets,
After being put in a quartz container and sealed with platinum foil, heat treatment is performed at 1160 ° C. or more and less than 1250 ° C.

In the present invention, zirconium oxide Z as a raw material is used.
Instead of rO ₂ , a mixture of zirconium oxide ZrO ₂ and a trace amount of yttrium oxide Y ₂ O ₃ is used, and this mixture and tungsten trioxide WO ₃ are mixed at a stoichiometric ratio of 1: 2 molar ratio. The heat-shrinkable oxide ZrW
_{2 Zr (1-x) Y} x W 2 O 8 in which a part of the zirconium Zr is replaced with yttrium Y of O ₈ is synthesized.

[0014]

Embodiments of the present invention will be specifically described below with reference to the drawings. 1 is an explanatory view showing a procedure of the method of the present invention, FIG 2 is heat-shrinkable oxide _{Zr (1-x)} synthesized by the method of the present invention _Hf x _{W 2} O 8, Zr
Is a graph showing a _(1-x) X-ray diffraction pattern of _{Y x} W 2 _{O 8.}

FIG. 1 shows a heat-shrinkable oxide Zr _(1-x) Hf
while indicating step of synthesizing _{x W 2 O 8, Zr (} 1- x) Y x W 2 O 8, the kind of raw materials to be mixed in the first step differs depending on the type of heat-shrinkable oxide ( First step (a)
To (d)), but the subsequent second to fourth steps are common regardless of the type of the heat-shrinkable oxide.

In the first step (a), a heat-shrinkable oxide ZrW is used.
₂ O ₈ is synthesized, and zirconium oxide ZrO is shown.
₂ and tungsten trioxide WO ₃ are mixed at a stoichiometric ratio of 1: 2 to obtain a raw material powder.

In the first step (b), the heat-shrinkable oxide HfW
₂ O ₈ is synthesized, and hafnium oxide HfO ₂
And tungsten trioxide WO ₃ are mixed at a stoichiometric ratio of 1: 2 to obtain a raw material powder.

In the first step (c), a heat-shrinkable oxide Zr _(1-x) Hf containing zirconium Zr and hafnium Hf is used.
_{xW 2} O ₈ (0 <x <1) is synthesized, and a mixture of zirconium oxide ZrO ₂ and hafnium oxide HfO ₂ and tungsten trioxide WO ₃ are mixed at a stoichiometric ratio of 1: 2 by mole. Mix to obtain raw material powder.

In the first step (d), a small amount of yttrium Y
Heat-shrinkable oxide containing _{Zr (1-x) Y x} W 2 O 8 (0
<X << 1) is synthesized, and a mixture of zirconium oxide ZrO ₂ and a trace amount (about 0 to 3%) of yttrium oxide Y ₂ O ₃ and tungsten trioxide WO ₃ in a stoichiometric ratio of 1: 2 Mix at stoichiometric ratio to obtain raw material powder.

In the second step, the raw material powder mixed in the first step is compressed by a tableting machine (not shown) or a press to a diameter of 10 m.
m, thickness 5 mm, and weigh about 1.5 g.

Next, in a third step, the pellets P are wrapped in a required number of pieces with platinum foil 1 or put in a quartz container 2 and the opening thereof is closed with platinum foil 3 and tied up with platinum wire 4 and sealed.

Then, in the fourth step, wrapping with platinum foil 1
Alternatively, the pellet P sealed with the platinum foil 3 was placed in the furnace 5 and heated to 1200 ° C. in the air. After heating the pellets P wrapped with the platinum foil 1 for 17 hours, the quartz container 2 containing the pellets P was heated for 140 hours and then rapidly cooled at room temperature. Then, in the process of wrapping with the platinum foil 1, about 4 g of the heat-shrinkable oxide could be synthesized. Further, in the process in which the heat-shrinkable oxide was placed in the quartz container 2, about 25 g of the heat-shrinkable oxide could be synthesized. Note that it was confirmed that the heat-shrinkable oxide according to the present invention was not synthesized when heated at 1150 ° C. or lower, and that the heat-shrinkable oxide according to the present invention was dissolved when heated at 1250 ° C. or higher. ,
1160 ° C or higher and lower than 1250 ° C.

FIG. 2 shows the heat-shrinkable acid thus synthesized.
Compound Zr_(1-x)Hf _xW₂O₈(X = 0,0.6,
It is a graph which shows the X-ray diffraction pattern of 1). This
Then, the heat-shrinkable oxide Zr_(1-x)Hf_xW₂O
₈ZrW from x = 0 to x = 1₂O₈(A = 9.15
Only peaks belonging to (5Å cubic)
It can be seen from this that the impurities have not been purified
You.

FIG. 3 shows a heat-shrinkable oxide Zr.
_(1-x)Y_xW₂O₈(X = 0,0.01,0.03,0.05)
3 shows an X-ray diffraction pattern of the sample. According to this, 1% substitution
Heat shrinkable oxide Zr_0.99Y_0.01W₂O₈Diffraction
The peak of the pattern is ZrW₂O₈Impure because it matches
It can be seen that the product was not purified, but 3% substitution and 5
% Substituted heat shrinkable oxide Zr_0.97Y_{0. 03}W₂O
₈And Zr_0.95Y_0.05W₂O₈Diffraction pattern
Then, ZrW ₂O₈Observed different peaks (arrows shown)
It can be seen that the impurities have been purified. I
Accordingly, zirconium Zr is replaced with yttrium Y.
In this case, it is desirable that the ratio be 1% or less.

The heat shrinkability of these samples was measured by high temperature X-ray diffraction.
evaluated. FIG. 4 shows ZrW using high-temperature X-ray diffraction peaks.₂
O₈5 shows the result of measuring the temperature change of the lattice constant of the sample. room temperature
Α region at ~ 123 ° C, γ region at 123-164 ° C, 16
Thermal contraction was observed in the β region above 4 ° C.
Has a coefficient of thermal expansion of α region: −10.2 × 10^-6K^-1  γ region: −16.6 × 10^-6K^-1  β region: −10.7 × 10^-6K^-1  It was measured.

[0026]

As described above, according to the present invention, heat-shrinkable oxides of extremely high purity can be synthesized in a large amount of 4.5 to 25 g at a time with simple equipment.
Since the equipment is simple and the work in each process is also easy,
This has an excellent effect that the production cost can be greatly reduced and the synthesis can be performed at low cost.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing the procedure of the method of the present invention.

Graph showing an X-ray diffraction pattern of Figure 2 _{Zr (1-x) Hf x} W 2 O 8.

3 is a graph showing an X-ray diffraction pattern of _{Zr (1-x) Y x} W 2 O 8.

FIG. 4 is a graph showing a change in lattice constant of ZrW ₂ O ₈ with temperature.

[Explanation of symbols]

 P ... Pellet 1 ... Platinum foil 2 ... Quartz container 3 ... Platinum foil 4 ... Platinum wire

 ──────────────────────────────────────────────────続 き Continued on front page (72) Inventor Tomoyuki Katsube 3-34 Funakoshi-cho, Yokosuka-shi, Kanagawa F-term (reference) 4G030 AA17 AA18 AA24 BA21 GA19 GA27 GA31 4G031 AA12 AA15 BA21 GA06 GA11 GA14

Claims (2)

[Claims] _1. Zr _(1-x) H having a negative coefficient of thermal expansion
_{f x W 2 O 8 (0} ≦ x ≦ 1) A process for the synthesis of heat-shrinkable oxide to synthesize, zirconium oxide ZrO ₂ and hafnium oxide HfO ₂
The raw material powder obtained by mixing any one or both of the above and tungsten trioxide WO ₃ at a stoichiometric ratio of 1: 2 is press-formed into pellets, and the pellets are wrapped with platinum foil, or A method for synthesizing a heat-shrinkable oxide, comprising: placing in a quartz container, sealing with platinum foil, and performing heat treatment at 1160 ° C. or more and less than 1250 ° C. 2. Zr _(1-x) Y having a negative coefficient of thermal expansion
_A method of synthesizing a heat-shrinkable oxide for synthesizing xW ₂ O ₈ (0 <x << 1), comprising: mixing a mixture of zirconium oxide ZrO ₂ and a trace amount of yttrium oxide Y ₂ O ₃ with tungsten trioxide WO ₃ The raw material powder mixed at a stoichiometric ratio of 1: 2 was press-molded into pellets, and the pellets were wrapped in platinum foil, or placed in a quartz container and sealed with platinum foil, and then heated to 1160 ° C. or higher.
A method for synthesizing a heat-shrinkable oxide, comprising performing heat treatment at a temperature of less than 250 ° C.