Crystal structure of A-site deficient La0.2Sr0.2-xCaxTiO3 perovskite at ambient conditions and high temperatures : a neutron powder diffraction study
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The crystal structures of several solid solutions of the perovskite La0.2Sr0.7-xCaxTiO3 were determined using the Rietveld analysis of neutron powder diffraction patterns collected at room temperature and at high temperatures. At room temperature, samples showed a tetragonal I4/mcm symmetry for compositions with 0.1 ≤ x ≤ 0.35 followed by a phase transition to orthorhombic Pbnm symmetry for compositions with 0.4 ≤ x ≤ 0.7. Samples with the orthorhombic symmetry showed two reversible phase transitions in the temperature range 20oC – 900oC. The first transition was a discontinuous Pbnm – I4/mcm around 300oC and the second was a continuous I4/mcm - Pm3 ̅m transition below 900oC. The lower symmetries resulted from very small distortions and changes in tilts of the BO6 octahedra of this perovskite; which was a direct result from the A-site ionic radius mismatch.
Aljaberi , A D & Irvine , J T S 2015 , ' Crystal structure of A-site deficient La 0.2 Sr 0.2-x Ca x TiO 3 perovskite at ambient conditions and high temperatures : a neutron powder diffraction study ' Dalton Transactions , vol 44 , no. 23 , pp. 10828-10833 . DOI: 10.1039/C5DT00238A
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The authors thank the Government of the United Arab Emirates for sponsoring this project, the EPSRC for Platform grant support and the Royal Society for a Wolfson Research Merit Award.
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