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  Sluchinskaya, I.A.; Lebedev, A.I.; Erko, A.: XAFS studies of the local structure and charge state of the Pr impurity in SrTiO₃. Physics of the Solid State 54 (2012), p. 975-979

10.1134/S1063783412050381

Abstract:
Solid solutions of (Sr1 – xPrx)TiO3 have been studied using Xray methods. It has been shown that, with an increase in the praseodymium concentration, the temperature of the structural phase transition to the phase with space group I4/mcm increases and, at x ≥ 0.15, the structure at 300 K is tetragonal. Xray absorption fine structure (XAFS) spectroscopy studies have revealed that Pr ions are predominantly in the charge state 3+ and occupy the Sr sites. No indications of the offcentering of Pr atoms at the Sr sites have been revealed. The local environment of Pr atoms is characterized by a strong relaxation of the oxygen atoms, the value of which corresponds to the difference between the ionic radii of Pr3+ and Sr2+. It has been found that, in the second shell, there occurs a significant repulsion of the Pr3+ and Ti4+ ions, which is responsible for the weak dependence of the lattice parameter in the solid solution on the praseodymium concentration.