Powder X-ray diffraction, infrared and conductivity studies of AgSbMP3O12 (M = Al, Ga, Fe and Cr)

New Nasicon type of compounds of composition AgSbMP3O12 (M = Al, Ga, Fe and Cr) are synthesized by solid-state method. All the compounds crystallize in the hexagonal lattice with space group R(3) over bar c. The infrared spectra of these compounds show characteristic bands due to PO4 group. The frequency independent conductivity of these compounds shows Arrhenius type behavior and the activation energy for conduction is in the range 0.40-0.55 eV. Frequency independent conductivity (sigma(de)) studies and frequency dependent (sigma(ac)) impedance measurements correlate well. The Cole-Cole plots do not show any spikes on the lower frequency side indicating negligible electrode effects. The activation energies obtained from the plots of log sigma T-dc versus 1/T log sigma(ac)(0) versus 1/T and log tau versus 1/T are approximately the same. The peak width at half height for electric modulus (AV) plot is similar to 1.24 decades for all samples, which is close to 1.14 decades observed for Debye solid. The height of electric modulus (M) obtained from the experimental plots are close to that of M (max) = C-0/2C indicating the Debye nature of the samples. (C) 2007 Elsevier Ltd. All fights reserved.