A New Solvent Solution Method to Prepare Cadmium Tungstate (CdWO4)

Cadmium tungstate (CdWO4) is a scintillation crystal material. It has a high density (7.9g/cm3), high effective atomic number, high light output value, short afterglow (Afterglow) and energy resolution, and it does no deliquesce in air. It is widely application prospects in industrial CT, medical CT and oil logging.

The preparation of cadmium tungstate powder has both its unique application value and raw materials for the later growth of cadmium tungstate single crystal. It can also efficiently explore the properties of different types and concentrations of ion doping for cadmium tungstate crystals.

The more commonly used cadmium tungstate powder system is a solvent solution method, but in the specific implementation process, since the solvent can be wrapped in the atomic skeleton formed by cadmium tungstate, so as to use in the process of suction filtration to remove impurities,  Pure water as a solvent will increase the volume of the sol obtained by the reaction, which will cause many adverse effects on the subsequent filtration process, which will not only prolong the filtration time, but also occupy a larger volume of the Buchner funnel.

In order to solve the shortcomings of the traditional process, some researchers have improved the solvent solution method. The improvement point is that no more pure water is used as the solvent. The specific experiment is:

1. Dissolving a certain amount of Na2WO4•2H2O in pure water and disposing it into a Na2WO4 aqueous solution having a concentration of 0.5 mol/L;

2. Dissolving a certain amount of Cd(NO3)2 in a sufficient amount of glycerol to prepare a Cd(NO3)2 glycerol solution having a concentration of 1.0 mol/L;

3. Take 10 mL of Na2WO4 aqueous solution and 5 mL of Cd(NO3)2 glycerol solution, mix well with each other, and stir at a temperature of 70 ° C for 1 h using a magnetic thermostat stirrer to obtain the sol volume only for the comparative example.  1 about 1/2 of a cadmium tungstate sol;

4. The sol that is reduced in size is subjected to suction filtration and decontamination operation using a suction filter device consisting of a Buchner funnel and a circulating water vacuum pump, and is filtered by multiple times, and the time of one suction filtration is about 25 minutes, and then placed in a constant temperature oven.  After sufficiently drying at a temperature of 40 °C, a granular solid sample is obtained;

5. The obtained particulate solid sample is placed in a muffle furnace and calcined at a high temperature of 800 °C for 1 h to substantially remove the residual glycerin present in the sample to obtain a cadmium tungstate powder.

Compared with the traditional solvent solution method using pure water as the reaction, the mixture of water-soluble alcohol and pure water is used as a solvent, thereby greatly reducing the volume of the cadmium tungstate sol, shortening the filtration time, and effectively improving the suction filtration. The efficiency, thereby improving the efficiency of preparing the cadmium tungstate powder, and producing a higher purity cadmium tungstate powder.

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