A phase transition with an abrupt electrical resistivity change around 800 K in BaBi 0.5Pb 0.5O 3

Abstract

Seebeck coefficient and electrical resistivity were measured in a temperature range of 300–1100 K in air for BaBi 1− x Pb x O 3 ( x=0, 0.25, 0.5, 0.75 and 1.0). The increase in Pb content led to the change in electrical conduction behavior from p-type semiconducting to n-type metallic and to n-type semimetallic, consistent with that in electronic structure previously reported on this alloy system. Two phase transitions were found at ∼650 K and ∼800 K for BaBi 0.5Pb 0.5O 3 from the temperature dependence of the electrical resistivity. With increasing temperature, the temperature dependence of the electrical resistivity for BaBi 0.5Pb 0.5O 3 showed a semiconductor-to-metal transition at ∼650 K with the continuous change in the resistivity and a metal-to-metal transition with an abrupt resistivity drop over ∼1.5 digits in a temperature range of 750–850 K (∼800 K). Combined with the powder X-ray diffraction (XRD) and Seebeck coefficient data, it is discussed that the semiconductor-to-metal transition at ∼650 K is due to the continuous proportionation of Bi cations into the chemical states closer to Bi 4+, and the metal-to-metal transition at ∼800 K may be due to the formation of a single chemical state with Bi 4+ which leads to the disappearance of the pseudogap at E F and the formation of a normal metal.