Dielectric relaxation studies on the submicron crystalline La2Mo2O9 oxide-ion conductors
Abstract Submicron crystalline La 2 Mo 2 O 9 bulk samples with grain size of about 0.3 μm were successfully synthesized by sol–gel method and sintering process assisted by phase transformation. In the dielectric measurement, two prominent relaxation peaks with almost the same height (P d1 at lower-temperature and P d2 at higher-temperature) are observed in temperature spectrum as well as in frequency spectrum, which are associated with the short-distance diffusion of oxygen vacancies. The activation energies and relaxation times at infinite temperature of these two peaks are deduced as (1.22 eV, 3.3×10 −16 s) and (1.35 eV, 5.9×10 −16 s), respectively. The DC conductivity of the submicron crystalline samples, which is about 0.02 S/cm when extrapolated to 800 °C, is much smaller than that of the macrocrystalline samples. The reciprocal of the peak height for P d1 peak is linearly proportional to temperature, while that for P d2 peak is temperature independent. The reason for the co-appearance and the possible relaxation dynamics of the two peaks are discussed.