Microwave sintering of nanopowder ZnNb_2O_6: Densification, microstructure and microwave dielectric properties

摘要

High density ZnNb_2O_6 ceramics were successfully fabricated by microwave sintering of ZnO-Nb_2O_5 and ZnNb_2O_6 nanopowders. Phase formation, microstructure and microwave electrical properties of the microwave sintered (MS) and microwave reaction sintered (MRS) specimens were examined using X-ray diffraction, field emission scanning electron microscopy and microwave dielectric properties measurement. Specimens were sintered in a temperature range from 950 to 1075 °C for 30 min at an interval of 25 °C using a microwave furnace operated at 2.45 GHz frequency, 3 kW power. XRD pattern revealed the formation of pure columbite phase of ZnNb_2O_6. The SEM micrographs show grain growth and reduction in porosity of specimens with the increase in sintering temperature. Good combination of microwave dielectric properties （ε_r~23.6， Qf~ 64，300 GHz and τ_f～-66 ppm/°C and ε_r~24， Qf~ 75，800 GHz and τ_f～-64 ppm/°C） was obtained for MS- and MRS-prepared samples at 1000 °C and 1050 °C for 30 min， respectively.