Sn-doping effect on dielectric properties of Ba(Ti1–<i>x</i>Sn<i>x</i>)O3 studied by x-ray absorption and emission spectroscopies

Significant enhancements of the dielectric and piezoelectric constants of Ba(Ti1−xSnx)O3 ceramics are of considerable interest in the quest for lead-free alternatives. The Sn-doping effect for x≤0.3 was investigated using x-ray absorption (XAS) and emission (XES) spectroscopy from a microscopic viewpoint. The Ti-K pre-edge XAS peak characteristic of Ti off-center displacement retains its intensity up to x=0.075, indicating the stability of the electric dipole moment at the Ti site, which was also confirmed by the locally sensitive charge-transfer peaks observed in Ti Kβ XES. In contrast, Sn L3-edge XAS shows a monotonic decrease in the characteristic peak intensity in the same x range, which is interpreted as the association of oxygen vacancies with Sn-doping at the Ti site based on the spectral simulation. The response to the electric field of the dipole moment at the Ti site becomes significant with the help of reduced dipole–dipole interaction by inevitably introduced oxygen vacancies, which leads to an enhancement of dielectric properties in the Sn low concentration range.