Local structure studies of SrTi16O3 and SrTi 18O3

Abstract

In this work we report on the local structure of Ti in SrTi 16O3 (STO16) and SrTi18O3 (STO18) investigated in the low temperature range (6-300 K) by extended x-ray absorption fine structure and x-ray absorption near edge structure (XANES) spectroscopy at Ti K-edge and by optical second harmonic generation (SHG). By comparing XANES of STO16 and STO18 we have identified the isotopic effect which produces at T < 100 K a noticeable difference in the measured mean square relative displacements (MSRD) of Ti-O1 bonds: while STO16 follow the expected Einstein-like behavior, for STO18 we have measured an increase of MSRD values with decreasing temperature. This is an indication of an increasing off-center position of the Ti atoms in the TiO6 octahedra. © 2014 The Royal Swedish Academy of Sciences.