Microwave dielectric properties of temperature stable MO-ZrO2-Ta2O5 ceramics

Temperature stable MO-ZrO2-Ta2O5 ceramics (M = Co, Ni) were prepared by solid state route. Crystal structure was determined by X-ray diffraction and Raman spectrum. Single-phase MZrTa2O8 was formed through the reaction between intermediate MTa2O6 and residual ZrO2. Quantitative phase analysis verified that changing temperature considerably adjusted the chemical compositions of ceramics. In the case of CoZrTa2O8, the optimum dielectric properties were epsilon(r)similar to 24.3, Q x f similar to 95,300 GHz (Q similar to 11,305 at 8.43 GHz), and tau(f)similar to -30.50 ppm/degrees C. The NiZrTa2O8 ceramic had epsilon(r) = 23.5, Q x f = 86,404 GHz (Q similar to 10,774 at 8.02 GHz), and tau(f)= -20.20 ppm/degrees C. Their large tau(f) values were compensated since MZrTa2O8 and MTa2O6 had opposite tau(f). Particularly, near zero tau(f) of -2.67 and 0.22 ppm/degrees C were obtained for M = Co, Ni at 1150 and 1175 degrees C, respectively. (C) 2019 Elsevier B.V. All rights reserved.