Negative Expansion Material-Yttrium Tungstate

At present, zirconium tungstate is the most widely studied negative thermal expansion material. AM₂O₈ series represented by ZrW₂O₈ has better negative thermal expansion performance and wider temperature range. In the existing academic papers, some scholars have introduced a process of preparing zirconium tungstate by multiple sintering solid-state method. Although this method can obtain single-phase zirconium tungstate products, it requires multiple sintering in the preparation process, and each sintering process parameters are changeable, the process is cumbersome and the conditions are not easy to control, and the requirements are too high.

In addition, some special rare earth tungstates, such as yttrium tungstate, have also been found to have negative thermal expansion properties. Yttrium tungstate was prepared from yttrium oxide powder and tungsten trioxide powder by solid state reaction and secondary sintering. The process is as follows:

Step 1: The yttrium oxide powder and tungsten trioxide powder are mixed evenly by wet ball milling method, and the raw material mixture is obtained by grinding after drying. The molar ratio of yttrium oxide powder and tungsten trioxide powder is 1:3.

Step 2: The raw material mixture in step 1 is roasted in a muffle furnace, crushed and grinded with the furnace after cooling, and the roasted product is obtained. The roasting temperature is 1050 ~1200 ℃, and the roasting time is 8h~10h.

Step 3: Place the calcined product in muffle furnace for secondary roasting treatment, crush and grind with the furnace after cooling, and get the secondary roasted product.
Step 4. The second roasting product was sifted through 80-400 meshes and the sifted product was removed to obtain yttrium tungstate powder. The Yttrium tungstate powder is a kind of negative thermal expansion material with excellent properties.

Solid-phase sintering of yttrium tungstate has the advantages of short preparation process, uniform solid-phase reaction, simple equipment requirement, low cost and suitable for large-scale production. In addition, the production process is pollution-free, environmentally friendly and the purity of the product is higher than 90%. Its cost is much lower than that of zirconium tungstate, and its performance parameters are close to each other.

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