Single-Crystal X-ray Diffraction Structure Analysis of PbNi_1/3Ta_2/3O₃ Relaxor Ferroelectric at Room Temperature

The structure of four single crystals of relaxor ferroelectric of nominal composition PbNi_1/3Ta_2/3O₃ have been studied by single-crystal X-ray diffraction at room temperature (cubic perovskite structure, space group \(Pm\bar {3}m~\left( {221} \right),~\) unit cell parameter a = 4.0287–4.0318 Å for different single crystals, refined to agreement factors R1 = 1.05–1.62%). The structural peculiarities (shift of the Pb atom from the ideal perovskite Wyckoff position 1a (0, 0, 0) by ~0.23 Å due to disordering of the atoms over six close-spaced Wyckoff sites 6e (x, 0, 0) along 〈100〉, deviation of the composition from the nominal one, etc.) are discussed.