Microwave dielectric properties of the (1-x)La(Nb0.9V0.1)O4-xCaMoO4 (0.05 ≤ x ≤ 0.50) scheelite solid solution ceramics

The CaMoO4 was added into La(Nb0.9V0.1)O-4 ceramics by solid state reaction method to adjust the temperature coefficient of frequency (TCF) values. The series of (1-x)La(Nb0.9V0.1)O-4-xCaMoO(4) (0.05 <= x <= 0.5) ceramics were sintered at 1060-1180 degrees C and found to possess permittivity (epsilon(r)) = 10.38-17.73, Q x f = 31,820-76,570 GHz (Q = 1/dielectric loss, f = resonant frequency lying between 8.5 and 9 GHz), and TCF = -26.3 similar to +160.7 ppm/degrees C. The structures of ceramic samples changed from monoclinic fergusonite to tetragonal scheelite continuously at x = 0.20 along with the shift of TCF values from positive to negative. The best microwave dielectric properties with epsilon(r) = 15.71, Q x f = 76,310 GHz (at 8.825 GHz), and TCF = - 26.3 ppm/degrees C were obtained in 0.8La(Nb0.9V0.1)O4-0.2CaMoO(4) ceramics sintered at 1160 degrees C and these ceramics might be good candidates for microwave devices. (C) 2019 Elsevier B.V. All rights reserved..