Microwave dielectric properties of hexagonal 12R-Ba3LaNb3O12 ceramics

The dielectric properties of dense ceramics of the n = 0 member of a newly identified homologous series Ba3+nLaNb3TinO12+3n, where n = 0, 1, and 2, are reported. Single-phase powders can be obtained from the mixed-oxide route at 1350 degrees C and dense ceramics (> 97% of the theoretical X-ray density) with uniform microstructures; (3-5 mu m) can be obtained by sintering in air at 1500 degrees C. The ceramics are excellent dc insulators with a band gap > 2.6 eV that resonate at microwave frequencies with a relative permittivity, epsilon(r) similar to 44, a quality factor, Q x f(r) of similar to 9000 at f(r) similar to 5.5 GHz and a temperature coefficient of resonant frequency, TCf similar to -100 ppm/K.