EXAFS study of lead-free relaxor ferroelectricBaTi1−xZrxO3at the ZrKedge

Abstract

Extended x-ray absorption fine structure experiments at the Zr $K$ edge were carried out on perovskite relaxor ferroelectrics $\mathrm{Ba}{\mathrm{Ti}}_{1\ensuremath{-}x}{\mathrm{Zr}}_{x}{\mathrm{O}}_{3}$ (BTZ) $(x=0.25,0.30,0.35)$, and on $\mathrm{Ba}\mathrm{Zr}{\mathrm{O}}_{3}$ for comparison. Structural information up to $4.5\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}}$ around the Zr atoms is obtained, revealing that the local structure differs notably from the average $Pm\overline{3}m$ cubic structure deduced from the x-ray diffraction. In particular, our results show that the distance between Zr atoms and their first oxygen neighbors is independent of the Zr substitution rate $x$ and equal to that measured in $\mathrm{Ba}\mathrm{Zr}{\mathrm{O}}_{3}$, while the x-ray cubic cell parameter increases linearly with $x$. Furthermore, we show that the Zr atoms tend to segregate in Zr-rich regions. We propose that the relaxor behavior in BTZ could be influenced by the random elastic fields generated by this particular chemical arrangement.