Structural, morphological and microwave dielectric studies on microwave sintered ZnWO4 ceramic compounds

The conventional solid-state reaction technique was employed to synthesis ZnWO4 ceramic compounds. The phase purity of as-synthesized compounds was investigated by powder X-ray diffraction technique and further confirmed by performing Rietveld refinement studies. The ZnWO4 compound observed to adopt monoclinic Wolframite crystal structure with P2/c space group. The sintering temperature of ZnWO4 was optimized through conventional resistive sintering process and found to be about 1100 oC for 3 h. To understand the role of microwave sintering on the microwave dielectric properties of ZnWO4, the compound was sintered in multi-mode microwave furnace at 1100 oC for 1 h, 2 h, and 3 h. Morphological studies on these compounds reveal that the microwave sintered compounds observed to possess higher density and lower grain size in comparison with conventional sintered compounds. The microwave dielectric properties such as dielectric constant (εr) and quality factor (Q × f) of both conventional and microwave sintered compounds were measured in frequency range of 8 – 12 GHz. The microwave sintered ZnWO4 at 1 h duration possess lower quality factor in comparison with the conventional sintered compounds. However, the quality factor observed to increases with increasing the sintering duration (2 h, and 3 h). The microwave sintered compound possesses slightly higher dielectric constant than the conventional sintered compounds and was attributed to higher densification. Raman spectra of the all the microwave sintered samples were collected and the variation in quality factor was explained with FWHM of A1g mode of ZnWO4 compound.