EXAFS studies of the local atomic structure of the lead free piezoelectric ceramics Kx Na1-x Nb O3 over the temperature range 10-1023 K

We use the x-ray absorption fine structure spectroscopy at Nb K edge to reveal the local atomic structure of Kx Na1-x Nb O3 (PSN) solid solutions. The study is performed over the temperature range 10-1023 K for six different x values. We show that only the combined analysis of extended x-ray absorption fine structure and preedge fine structure provides complete and reliable information about the local structure of Nb O6 octahedra. Such extensive treatment of the experimental data shows that the local structure of PSN could be described within the spherical model proposed earlier as a hypothesis for perovskite-type ferroelectric zirconates. We reveal that the Nb atoms are localized near their average positions on the sphere surfaces for all temperatures and x values. With regard to previous results we point out the features of microscopic structure common for PSN and perovskite-type zirconates.