Effect of Synthesis Atmosphere on the Microwave Dielectric Properties of ZnO Powders

ZnO powders were prepared via the solid-state reaction at 800 degrees C in air, nitrogen, and hydrogen atmospheres, respectively. Raman spectra show that the concentration of oxygen vacancies greatly increases when the sample is prepared in hydrogen atmosphere. The particle size distributions of the powders prepared in air and nitrogen atmospheres are better than that in hydrogen atmosphere. The dielectric parameters of the samples were determined in the frequency range of 8.2-12.4 GHz. Results show that the real part epsilon' and imaginary part epsilon ' of complex permittivity of the sample prepared in hydrogen atmosphere reveal the greatest values in three samples. The loss mechanism of the samples was discussed.