The cubic zirconium tungstate is one of the hotspots in the research of negative thermal expansion materials, with its widest range of negative expansion effect, high negative expansion coefficient and isotropy and other advantages, it can be combined with positive expansion into the specific materials with zero or low expansion, and thus to be used in the some devices which is used under extreme temperature conditions field of aerospace. The preparation methods of zirconium tungstate are solid phase sintering, sol-gel, combustion, chemical coprecipitation and microwave method ect., however, the zirconium tungstate particles or whiskers prepared by these methods are irregular, and can not be used in some specific fields, such as aerospace.

 

There is an invention disclosed a method for preparing nanoscale zirconium tungstate hollow sphere by hydrothermal synthesis method from the raw materials of ammonium metatungstate (AMT) and zirconium oxychloride, with the steps as following:

1. Respectively weight the right amount of ammonium metatungstate and zirconium oxychloride according to the stoichiometric ratio of zirconium tungstate (ZrW₂O₈), respectively, and prepare zirconium oxychloride aqueous solution and ammonium metatungstate aqueous solution respectively;

2. Add zirconium oxychloride aqueous solution into ammonium metatungstate aqueous solution under the condition of stirring, then preheat the mixture at  the temperature of 60～70℃ with stirring continuous;

3. Add hydrochloric acid solution with continuously stirring, and then heat the solution to 80~100℃, then we get the zirconium tungstate precursor suspension after keeping the temperature for a proper time;

4. The zirconium tungstate precursor suspension is carried out a hydrothermal reaction at a temperature of 170~190℃, followed by cooling, collecting the precipitate and washing to remove chloride ions (Cl^- ), drying, calcining at 800~1000℃, and finally to obtain nanoscale zirconium tungstate hollow sphere.

 

In this method of preparing zirconium tungstate by using AMT as raw material, due to the hydrothermal synthesis method can truly realize synthesizing zirconium tungstate powder at a low temperature, cut down the synthesis time of the precursor and control the direction of crystal growth; thus, the prepared nanoscale zirconium tungstate hollow sphere has the benefits of uniform particle size, good negative expansion performance and low density ect., and to have great potential for applying in aerospace field.