Preparation, characterization and impedance study of AgTaMP3O12 (M=Al, Ga, In, Cr, Fe and Y)

Preparation, characterization and electrical properties of new silver nasicons of composition AgTaMP3O12 (M=Al, Ga, In, Cr, Fe and Y) have been investigated. All compositions crystallize in the rhombohedral nasicon structure and are found to be isomorphous with NbTiP3O12. The space group of all compositions is R3¯c except AgTaYP3O12, which crystallizes in R3¯ space group. All the compounds show characteristic PO4 vibrational bands. DC conductivity studies (by two-probe method) and AC impedance measurements correlate well. The Cole–Cole plots do not show any spikes on the lower frequency side indicating negligible electrode effects. The isothermal conductivity obtained from DC (σdc) and AC (σ(0)) agrees well. The activation energies obtained from the plots of log σdc versus 1 / T, log σ(0) versus 1 / T and log τ versus 1 / T are approximately the same suggesting conducting species to be mobile silver ions. The peak width at half height for Mʺ modulus plot is ∼1.34 decades for all samples, which is close to 1.14 decades observed for Debye solid. The height of Mʺ obtained from the experimental plots are close to that of Mʺ (max) = C0 / 2C indicating the Debye nature of the samples. The room temperature Mössbauer spectrum of AgTaFeP3O12 suggests paramagnetic nature of this sample.