Successive phase transitions in the highly ordered complex perovskite PbLu1/2Nb1/2O3

The structural phase transitions and the electrical behaviour of the complex perovskite PbLu1/2Nb1/2O3 have been investigated using X-ray powder diffraction, dielectric constant measurements, differential scanning calorimetry and measurement of the polarisation as a function of applied electric field. The high-temperature paraelectric phase is highly ordered. A first-order paraelectric-antiferroelectric phase transition occurs at 270 degrees C and an antiferroelectric-ferroelectric phase transition, characterised by dispersion in the curves of dielectric constant as a function of temperature, occurs at approximate to 30 degrees C. The antiferroelectric phase is isostructural with the orthorhombic form of PbYb1/2Nb1/2O3.. The low-temperature ferroelectric phase also has an orthorhombic crystal structure.