Temperature dependent XAFS studies of local atomic structure of the perovskite-type zirconates

Abstract

Temperature dependent preedge and extended x-ray absorption fine structure measurements at the Zr $K$ edge for the perovskite-type zirconates $\mathrm{Pb}{\mathrm{Zr}}_{0.515}{\mathrm{Ti}}_{0.485}{\mathrm{O}}_{3}$ (PZT), $\mathrm{Pb}\mathrm{Zr}{\mathrm{O}}_{3}$ (PZ), and $\mathrm{Ba}\mathrm{Zr}{\mathrm{O}}_{3}$ are performed. To carry out a more accurate study of the weak reconstruction of the local atomic structure we employed a combination of two techniques: (i) analysis of the preedge fine structure, and (ii) analysis of the Fourier transform of the difference between $\ensuremath{\chi}(k)$ functions obtained at different temperatures. A detailed investigation of local atomic structure in the cubic phase for all the crystals is also performed. It is shown that neither the displacive nor the order-disorder model can describe correctly the changes of local atomic structure during phase transitions in PZ and PZT. A spherical model describing the local atomic structure of perovskite-type crystals suffering structural phase transitions is proposed.