Low temperature synthesis and dielectric characterisation of La ₂ Mo ₂ O ₉ ceramic at RF and microwave frequencies

Using a simple solid-state mixed oxides method, dense La2Mo2O9 ceramics with a relative density higher than 94% were prepared at relatively low sintering temperatures (<960°C) and the crystal structure, dielectric properties were studied in some details. Splitting peaks in XRD profiles evidenced the presence of monoclinic phase. Optimum dielectric properties at microwave frequency were achieved in the best-sintered sample at 920°C, with a moderate relative permittivity of 20.6, a temperature coefficient of the resonance frequency of −38 ppm/°C, but a relatively low quality factor Q×f ∼ 7,160 GHz (f = 9.7 GHz). Complex impedance analysis revealed a thermally activated process derived from the successive short-distance diffusion of oxygen vacancies in the present La2Mo2O9 ceramics, accounting for the low quality factor.