Structural investigations of the bismuth scandate-lead titanate xBiScO_3-(1-x)PbTiO_3 solid solution for 0.10 ≤x≤ 0.40

摘要

A full structural study of the solid solution xBiScO_3-(1-x)PbTiO_3 (BS-PT) has been carried out by neutron powder diffraction using the General Materials Difrractometer (GEM) at ISIS facility in Oxford and complemented by in-house x-ray diffraction studies and high-temperature dielectric measurements. Atomic positions and thermal-displacement parameters have been determined by Rietveld refinement of neutron powder-diffraction data for a total of 14 different compositions of BS-PT, where 0.10≤x:≤0.40. A gradual structural phase transition from a tetragonal (space group: PAmm) phase to a rhombohedral (space group: R3m) phase as a function of composition has been observed and the phase boundary is identified as a mixture of a tetragonal and a monoclinic phase with space group Cm. However, the refined anisotropic thermal parameters in the region x≥0.39 are found to be unrealistic for the average crystal structure and instead of a rhombohedral phase, a monoclinic phase (Cm) is suggested for the compositions x ≥ 0.39. In addition, temperature-dependent dielectric measurements have been carried out to demonstrate the physical properties of the ceramics including ferroelectric transition temperatures as a function of composition.