Phase transformation and microwave dielectric properties of Ba4LiTa3-x SbxO12

A series of Ba4LiTa3-xSbxO12 ceramics were prepared by the conventional solid-state ceramic route. A phase transformation from hexagonal to cubic was detected with increasing Sb content. Ba4LiTa3O12-type hexagonal structure formed when x <= 1.5, whereas Ba4LiSb3O12-type cubic structure appeared at x >= 2. The microwave dielectric properties of the ceramics exhibited a significant dependence on the composition. The relative permittivity (epsilon(r)) decreased from 28 at x=0 to 20.2 at x=3, the quality factor (Q x f) values ranged from 103,617 to 26,100 GHz and the temperature coefficient of resonant frequency (tau(f)) changed from positive +24.1 ppm/degrees C to negative 30 ppm/degrees C. A temperature-stable ceramic with x=1.0 was achieved with epsilon(r)similar to 25.1, Q x f similar to 77,700 GHz and tau(f) similar to-3.6 ppm/degrees C. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.