Anomalous temperature-dependent electrical properties of Na2MnP2O7

Na2MnP2O7 is a promising sodium-ion battery cathode material. In our work we analyse electrical properties of Na2MnP2O7 ceramics by impedance spectroscopy in the broad frequency range from 10 Hz to 10 GHz. Temperature dependencies of conductivity indicated a phase transition taking place in the grains of ceramics at 663 K, which was also evidenced by differential thermal analysis and thermal X-ray diffraction. In addition, close to the room temperature protonic conductivity strongly influences the total conductivity of the ceramics. Both newly observed phenomena may be important for overall sodium battery performance.