Composition-dependent metal-insulator transition in perovskite Ca _XPb _((1-X)) TiO _3 (CPT) ceramic

摘要

Ceramic compositions of a complex perovskite Ca _XPb_((1-X))TiO _3 (CPT) systems with x=0.6, 0.7 and 0.8 were prepared by mechanical mixing of their oxides (CaTiO _3 and PbTiO _3). The structure of the (CPT) ceramics was characterized by X-ray diffraction (XRD) The ceramics transform gradually from orthorhombic phase (pseudo cubic phase) to cubic phase by increasing pb content percent. The dc resistivity ρ(t) versus temperature (range 300-525 K) for x=0.6, 0.7 and 0.8. The ρ.T/curves reveal that samples exhibit a metallic behaviour at low temperature and undergo a metal-semiconductor transition with increasing temperature at T _p=373 K, 343 K and 333 K, for x=0.6, 0.7 and 0.8, respectively. The nature of conduction mechanism is studied in semiconductor region by studying the current-voltage temperature characteristics. The current-voltage characteristics were interpreted in terms of Poole-Frenkel type of conduction mechanism.