German Conference for Research with Synchrotron Radiation, Neutrons and Ion Beams at Large Facilities

Low-temperature phase transitions in PrAlO3–SrTiO3 series

17 Sept 2018, 16:30

1h 30m

Fakultät für Maschinenwesen der Technischen Universität München

Poster P8 Functional materials and materials science Poster session 1

Speaker

Anatoliy Senyshyn

Description

Phase and structural behaviour of the continuous perovskite solid solution Pr_1-xSr_xAl_1-xTi_xO₃ have been studied in the temperature range 20 – 295 K by high-resolution X-ray synchrotron powder diffraction. Superb characteristics of the beamline ID22@ESRF allows to detect either subtle spiting of the main perovskite maxima and/or appearance of weak superstructure reflections, thus proving diverse variants of perovskite structure existing in Pr_1-xSr_xAl_1-xTi_xO₃ series at different compositions and temperatures. It was revealed that the samples with x = 0.1 and 0.2 undergo a sequence of structural phase transitions R-3c – Immb – I2/m, similar to those observed for the parent PrAlO₃ phase. These LT transitions in praseodymium aluminate are unique among all RAlO₃ perovskites and are considered to be caused by the electronic effects involving Pr³⁺ ions, e.g. a coupling between Pr³⁺ electronic states and phonons and/or cooperative Jahn-Teller effects. It was established that temperatures of both R-3c – Immb and Immb – I2/m transitions in Pr_1-xSr_xAl_1-xTi_xO₃ series systematically decrease from 205 K and 151 K for PrAlO₃ to 170 K and 90 K for x = 0.2 sample. Quite different phase behaviour was observed in the SrTiO₃-rich part of the system. Simultaneous aliovalent substitution of Sr²⁺ and Ti⁴⁺ species by 10 % Pr³⁺ and Al³⁺ ions increases the temperature of a Pm3m – I4/mcm transition from 105 K in SrTiO₃ to ~250 K in Pr_0.1Sr_0.9Al_0.1Ti_0.9O₃.