Local A-Site Layering in Rare-Earth Orthochromite Perovskites by Solution Synthesis

Luke M Daniels; Reza J Kashtiban; Demie Kepaptsoglou; Quentin M Ramasse; Jeremy Sloan; Richard I Walton

doi:10.1002/chem.201604766

Local A-Site Layering in Rare-Earth Orthochromite Perovskites by Solution Synthesis

Chemistry. 2016 Dec 19;22(51):18362-18367. doi: 10.1002/chem.201604766. Epub 2016 Nov 3.

Authors

Luke M Daniels¹, Reza J Kashtiban², Demie Kepaptsoglou³, Quentin M Ramasse³, Jeremy Sloan², Richard I Walton¹

Affiliations

¹ Department of Chemistry, University of Warwick, Coventry, CV4 7AL, UK.
² Department of Physics, University of Warwick, Coventry, CV4 7AL, UK.
³ SuperSTEM Laboratory, SciTech Daresbury Campus, Daresbury, WA4 4AD, UK.

Abstract

Cation size effects were examined in the mixed A-site perovskites La_0.5 Sm_0.5 CrO₃ and La_0.5 Tb_0.5 CrO₃ prepared through both hydrothermal and solid-state methods. Atomically resolved electron energy loss spectroscopy (EELS) in the transmission electron microscope shows that while the La and Sm cations are randomly distributed, increased cation-radius variance in La_0.5 Tb_0.5 CrO₃ results in regions of localised La and Tb layers, an atomic arrangement exclusive to the hydrothermally prepared material. Solid-state preparation gives lower homogeneity resulting in separate nanoscale regions rich in La³⁺ and Tb³⁺ . The A-site layering in hydrothermal La_0.5 Tb_0.5 CrO₃ is randomised upon annealing at high temperature, resulting in magnetic behaviour that is dependent on synthesis route.

Keywords: chromites; electron energy loss spectroscopy (EELS); hydrothermal synthesis; magnetism; perovskites.