Calcining temperature dependence of microwave dielectric properties of (1-x)ZnAl2O4 xTiO2 (x=0.21) ceramics

(1 - x)ZnAl2O4-xTiO(2) (x = 0.21) ceramics were synthesized at 1500 degrees C using the solid-state reaction after the starting powders were calcined at 1050-1250 degrees C. The effects of calcining temperature on the microstructures, phase compositions, and microwave dielectric properties of the ceramics had been investigated. In the calcined (1 - x)ZnAl2O4-xTiO(2) (x = 0.21) powders, the amount of the secondary phase Zn2Ti3O8 decreases gradually with increasing calcining temperature and it disappears at more than 1150 degrees C. The epsilon(r) and Q . f values increase slowly with increasing calcining temperature and then decrease after reaching the maximum value at 1150 degrees C, whereas the tau(f) values are nearly independent of the calcining temperature and approach zero. When the calcining temperature reaches 1150 C, the optimal microwave dielectric properties of the (1 - x)ZnAl2O4-xTiO(2) (x = 0.21) ceramics can be exhibited with a epsilon(r) of 11.6, a Q . f of 74,000 GHz (at about 6.5 GHz), and a tau(f) of -0.4ppm/degrees C.