Unusual phase coexistence regime across the ferroelectric - paraelectric transition

RESUMO

A PbTiO3 epitaxial thin film grown on a DyScO3 substrate was studied by x-ray diffraction in the temperature range of 20-500 degrees Celsius. It is found that the ferroelectric to paraelectric phase transition proceeds through a peculiar transitional coexistence state extending between 402 degrees Celsius and 414 degrees Celsius. Within this temperature interval, at a temperature of 405 degrees Celsius, a domain structure transition occurs, at which the three-domain c/a1/a2 polytwin phase transforms into an ordinary c/a2 twinned phase. It is proposed that the coexistence of two independent twinned phases with the paraelectric phase is enabled by vertical strain gradients in the film.