Defects, Structure Changes, and the Effect of Random Fields on the Displacement of Off‐Center Ions in Sr_0.5Ba_0.5Nb₂O₆ Doped with Combinations of Ce and Cr

Abstract

Synchrotron X‐ray powder diffraction data are analyzed in detail by the Rietveld structure refinement program to obtain microscopic structure changes of Sr0.5Ba0.5Nb2O6 (SBN50) doped with combinations of Ce and Cr. The defects of Ce and (Ce,Cr)‐doped SBN50 are determined by the densification behavior, and it is found that creation of Nb vacancies and self‐compensation are the defect reactions for Ce and (Ce, Cr) dopants, respectively. The variations of the lattice parameters of a and c axes with doping content are determined by the changes of the distance between A1 and A2 sites via Coulomb interactions and the mean bond length of Nb(1)–O(4), respectively. It is confirmed that the polarization of SBN50 is mainly determined by the displacement of Nb ions. The effect of random fields induced by the impurities of the combinations of Ce and Cr on the displacement of off‐center Nb ions has been reasonably explained.

Local environments and transport properties of heavily doped strontium barium niobates Sr0.5Ba0.5Nb2O6

“…Doping is expected [55] , [56] to further decrease thermal conductivity, but is mainly investigated in hopes of achieving good values of electrical conductivity (σ) and Seebeck coefficient (S), which are generally too low. However, only doping of SBN materials at low levels (few %) has been investigated largely [8,15,22,23,28,35,36,38,39,53,[57][58][59][60][61][62][63][64], while it would be highly desirable to explore the feasibility and effectiveness of doping at high levels, when doping is expected to affect the whole band structure in addition to a simple injection of electrons or holes.…”