Polarization at the compositional interface in Nb-doped metastable TiO₂-SnO₂ solid solutions

Abstract

Polarization architecture was incorporated into metastable Nb-doped TiO2-SnO2 to deliver electron accumulation at the localized TiO2-SnO2 compositionally fluctuating interface. Specimens were quenched from various holding temperatures to ambient temperature in air to avoid bimodal decomposition into TiO2 and SnO2 endmembers. At the lowest sintering temperature of 1,400°C, the mixed phase containing TiO2- and SnO2-rich compositions existed as an intermediate state to the single-phase solid solution. The phase boundary became more ambiguous with increasing sintering temperature, and the compositional fluctuation size reduced to single nanometers at 1,500°C. The permittivity due to the interfacial polarization, ε interface, increased steadily with increasing sintering temperature. The larger ε interface values at higher temperatures are attributed to the greater density of the compositionally fluctuating phase interface, which leads to greater electron accumulation at the energy barrier between the two semiconducting layers.