Microwave dielectric properties of hexagonal, perovskites

The dielectric properties of the hexagonal perovskite oxides, La4BaTi4O15, La4Ba2Ti5O18 and Ba5Nb4O15 have been characterized at microwave frequencies. These systems combine a relatively high permittivity (39 < epsilon(T) < 46) with a low dielectric loss (11,583 < Q.f < 31,839) and small temperature coefficient of resonant frequency (-36 < tau(f) < 79) and may be suitable for application as dielectric resonators. The dielectric polarizability of each compound was compared to values predicted from the sum of tabulated empirical ion dielectric polarizabilities. From these analyses it was concluded that published values for the ion polarizability of La are high; self consistent results for these and other La-containing oxides can be obtained with alpha(La) = 4.82(Angstrom(3)).