The influence of Fe, Cu, Al-doping on the crystal structure, thermal and electrical properties of calcium titanate

Abstract

CaTi(1-x)M(x)O(3-delta) (M=Fe, Al, Cu) samples were synthesized by the standard ceramic technology. The stability areas and the crystal structure of the solid solutions were determined by the X-ray Diffraction technique. CaTi(1-x)Fe(x)O(3-delta) system in the interval from 0 up to 0.5 had a perovskite-like homogeneous phase. In CaTi(1-x)Al(x)O(3-delta) system in the range of 0 <= x <= 0.2, a solid solution with orthorhombic structure was found. In CaTi(1-x)Cu(x)O(3-delta) system a solid solution existed in the interval of structures 0 <= x <= 0.1. When the content of copper was more than 0.15 (x>0.15) other phases were observed. Unit cell parameters were defined by Rietveld method. Additionally, the electrical and thermal properties of the single phase compounds were investigated. It was concluded that all of the compounds are semiconductors with different main types of charge carriers, depending on the partial pressure field. Usually they present p-type conductivity in the high oxygen pressure region, ionic conductivity in middle pressures and n-type in the low oxygen pressure field, Finally, the thermal expansion coefficients of the samples in different temperature regions were determined. (C) 2008 Elsevier B.V. All rights reserved.