Impedance spectroscopic investigation on electrical conduction and relaxation in manganese substituted pyrochlore type semiconducting oxides

The effect of simultaneous substitutions of Mn in both A and B sites of the pyrochlore type semiconducting oxides: (CaCe1−2xMn2x)(Sn1−xMnxINb)O7−δ (x=0, 0.1, 0.2, 0.3 and 0.4) on the electrical conduction and relaxation was studied in detail using impedance analysis as a function of frequency over a wide range of temperature. Impedance and modulus analysis clearly explain the relaxation in these materials and its dependence on Mn concentration. Grain boundary dominant electrical characteristics have been observed with progressive Mn substitution. Correlated barrier hopping model was successfully applied for explaining the conduction mechanism in these compounds. Variation of hopping parameters with Mn substitution in these materials indicates strong dependence on the grain and grain boundary contributions. This insight to the conduction mechanism of the system offers in tuning the electrical properties for desired applications such as NTC thermistors.