Insulator–metal transition in Mn-doped NaNbO₃ induced by chemical and thermal treatment

Abstract

The transition between insulator and metal conductor states, induced by oxygen non-stoichiometry, was studied for NaNbO₃ : Mn crystals. Conditions for an optimal reduction were determined on the basis of TGA tests. The temperature dependencies of the resistance measured on the macroscale showed that the transition from thermally activated to metallic features depends on the level of oxygen deficiency. The LC-AFM measurement exhibited non-homogeneous electric resistance on the nanoscale. We ascribed the local insulator–metal transition to changeover in the electronic state of the Nb ions occurring in filaments. The Mn dopant stabilised the induced oxygen non-stoichiometry and the metallic conduction down to room temperature.

Keywords:

• extended defects
• insulator–metal transition
• LC-AFM
• NaNbO₃
• TEM

Acknowledgements

The authors thank Dr A. Besmehn and to Ms V. Lenzen from Forschungszentrum Jüelich GmbH, 52425 Jüelich, Germany, for carrying out the XRD test.