Local structure inBaTiO3−BiScO3dipole glasses

Abstract

Local structures in cubic perovskite-type (Ba 0.6 Bi 0.4)(Ti 0.6 Sc 0.4)O 3 solid solutions which exhibit reentrant dipole glass behavior have been studied with variable-temperature X-ray/neutron total scattering, extended X-ray absorption fine structure, and electron diffraction methods. Simultaneous fitting of these data using a Reverse Monte Carlo algorithm provided instantaneous atomic configurations which have been used to extract local displacements of the constituent species. The smaller Bi and Ti atoms exhibit probability density distributions which consist of 14 and 8 split sites, respectively. In contrast, Ba and Sc feature single-site distributions. The multi-site distributions arise from large and strongly anisotropic offcenter displacements of Bi and Ti. The cation displacements are correlated over a short range, with a correlation length limited by chemical disorder. The magnitudes of these displacements and their anisotropy, which are largely determined by local chemistry, change relatively insignificantly on cooling from room temperature. The structure features a non-random distribution of local polarization with lowdimensional polar clusters that are several unit cells in size. In situ measurements of atomic pairdistribution function under applied electric field were used to study field-induced changes in the local structure; however, no significant effects besides noticeable lattice expansion in the direction of the field could be observed up to electric-field values of 4 kV/mm.

Field-induced polarization rotation and phase transitions in 0.70Pb(Mg1/3Nb2/Hou1, Usher2, Fulanović3 et al. 2018Phys. Rev. B30190View full textAdd to dashboardCite

“…The in situ PDF technique, first reported by Usher et al, 36 has been applied to various compositions of piezoceramics. 36,56,57 Figure 6 shows the in situ PDF patterns of PMN- The behavior of the PDF peak at r≈3.5 Å can be interpreted in terms of the Pb 2+ displacements, which are commonly observed in Pb-based perovskites and are expected to be significantly larger than those of B-sites ions. Even though the changes of polarization cannot be fully described since X-ray PDF is not sensitive to the oxygen positions, the Pb 2+ displacement can still be used to interpret the local structural changes under fields.…”

Designing pseudocubic perovskites with enhanced nanoscale polarization

“…For example, a combination of large Ba (A-site) and Sc (B-site) ions in the BaTiO3-BiScO3 solid solutions [26] limit the correlations among the Bi and Ti displacements to only 1-2 perovskite unit cells. In contrast to Sc, the non-ferroelectric Zn cations can form covalent bonds with oxygen and are known to support a large tetragonal distortion in BiZn½Ti½O3 [27,28]. Therefore, the BaTiO3-BiZn½Ti½O3 solid solutions, while also pseudocubic, feature more extended distorted regions [29] than BaTiO3-BiScO3 [26] because Zn ions are less effective disruptors of correlations than Sc.…”

Effect of A‐site substitutions on energy storage properties of BaTiO3‐BiScO3 weakly coupled relaxor ferroelectrics

“…The peak at r ~ 2.3 Å is due to shorter Bi-O bond lengths caused by off-centered displacement of Bi along the <111> and <100> directions. 47 In addition, shoulders appear on both side of the main A-O peak at r ~ 2.8 Å. Such splitting of the A-O peak was also observed for Pb-based relaxors such as Pb(Mg 1/3 Nb 2/3 )O 3 and could be attributed to off-centering of the A-site cation.…”

“…In addition, we observe a four‐way splitting of the A‐O bond distances. The peak at r ~ 2.3 Å is due to shorter Bi‐O bond lengths caused by off‐centered displacement of Bi along the <111> and <100> directions . In addition, shoulders appear on both side of the main A‐O peak at r ~ 2.8 Å.…”