Temperature-dependent neutron diffraction study at the morphotropic phase boundary of $$(1-x)$$Bi(Fe2/8Ti3/8Mg3/8)O₃–xPbTiO₃†

The ferroelectric ceramic (0.675)Bi(Fe 2/8 Ti 3/8 Mg 3/8 )O ₃ –(0.325)PbTiO ₃ is attractive because it contains low-lead content with a competitive piezoelectric coefficient, d₃₃ of 100 pC/N. It also has a high-Curie temperature, ( TC ) of 650 °C, although d₃₃ reduces above 100 °C, being 0 pC/N at ( Td ) = 525 °C. We clarified its temperature-dependent structure–property relationships on the average scale. Rietveld analysis against neutron powder diffraction, revealed three phase transitions: Cc + P4mm from RT to 600 °C; Cc + Pm 3̄ m from 610 to 680 °C; and Pm 3̄ m above 680 °C, over TC . Dielectric permittivity increases at 610 °C, matching the symmetry change from P4mm to Pm 3̄ m. A broad diffuse phase transition is observed over a Curie range of 70 °C in the region Cc + Pm 3̄ m, potentially due to presence of microregions with local compositions different from the average composition over short length scales.