Defect structure of acceptor-doped calcium titanate at elevated temperatures

Abstract

The defect structure of acceptor (Al or Cr)-doped polycrystalline calcium titanate was investigated by measuring the oxygen partial pressure dependence (at 10° to 10−18 atm) of the electrical conductivity at 1000 and 1050° C. The observed electrical conductivity data were proportional to $P_{{\text{O}}_{\text{2}} }^{ - {1 \mathord{\left/ {\vphantom {1 4}} \right. \kern-\nulldelimiterspace} 4}}$ for the oxygen pressure range < 10⁻¹⁰ atm and proportional to $P_{{\text{O}}_{\text{2}} }^{ + {1 \mathord{\left/ {\vphantom {1 4}} \right. \kern-\nulldelimiterspace} 4}}$ for the oxygen pressure range ( 10⁻⁷ atm. The conductivity values were observed to increase with the acceptor concentration in the p-type region with the shift in the conductivity minima towards lower oxygen partial pressure. The absolute value of the electrical conductivity in the acceptor-doped samples were lower in the n-type region compared to the values in the undoped CaTiO₃. Aluminium and chromium were found to be equally effective in acting as acceptor impurities in CaTiO₃. The defect chemistry of CaTiO₃ is dominated by the added acceptor impurities for the entire oxygen partial pressure range used in this investigation.