On the physical and semiconducting properties of the crednerite AgMnO2 prepared by sol-gel auto-ignition

AgMnO2 prepared by sol-gel auto-ignition, crystallizes in the crednerite type structure with a monoclinic symmetry (Space Group: C2/m), supported by the Raman spectroscopy. The structure, deriving from the delafossite, is elongated along the c-axis (c/a = 1.12), due to the Jahn-Teller (J-T) Mn3+ ion. The thermal analysis (TGA) shows a stability up to 630 degrees C before its reduction into Ag and Mn2O3, which is confirmed by the DTA plot. The optical transition (1.82 eV) between the bands edges is directly allowed. The magnetization at saturation (M-S), the coercitive field (H-C) and remanent field (M-R) obtained from the vibration sample magnetometry are 0.16 emu/g, 205 Oe and 6.75 x 10(-3) emu/g respectively. The electrical conductivity is frequency dependent and follows an exponential law. Moreover, the metal-metal interaction is weakened by the longer Ag-Ag length (2.89 nm). The thermoelectric power confirms the p-type character of AgMnO2 (hole-doped crednerite). The conduction mechanism is thermally activated and occurs through nearest neighboring hopping among Ag2+/+. The activation energy decreases with increasing the frequency, indicating that the mobility is thermally activated rather than the holes density.