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Rare earth indates (RE: La-Yb): Influence of synthesis route and heat treatment on crystal structure

Abstract

Rare earth indates are an interesting class of compounds with rich crystallography. The present study explores the crystallographic phases observed in REInO3 (RE: La-Yb) systems and their dependence on synthesis routes and annealing temperature. All REInO3 compositions were synthesized by solid state route as well as gel-combustion synthesis (GC) followed by annealing at different temperatures. The systems were well characterized by powder XRD studies and were analysed by Rietveld refinement for the structural parameters. The cell parameters were observed to decrease in accordance with the trend in ionic radii on proceeding from lighter to heavier rare earth ions. Interestingly, the synthesis route and the annealing temperature had profound bearing on the phase relations observed in REInO3 series. The solid state synthesized samples depicted an orthorhombic phase (Pbnm) field for LaInO3 to SmInO3, followed by a hexagonal-type phase (P63cm) for GdInO3 to DyInO3. However, the phase field distribution was greatly influenced upon employing gel-combustion (GC) wherein both single-phasic hexagonal as well as orthorhombic phase fields were found to shrink. Annealing the GC-synthesized compositions to still higher temperatures (1250oC) further evolved the phase boundaries. An important outcome of the study is observance of polymorphism in SmInO3 which crystallized in hexagonal phase when synthesized by GC and orthorhombic phase by solid state synthesis. This reveals the all-important role played by synthesis conditions. The existence and energetics of the two polymorphs have been elucidated and discussed with the aid of theoretical studies.

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Publication details

The article was received on 22 Dec 2017, accepted on 01 Apr 2018 and first published on 02 Apr 2018


Article type: Paper
DOI: 10.1039/C7DT04849A
Citation: Dalton Trans., 2018, Accepted Manuscript
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    Rare earth indates (RE: La-Yb): Influence of synthesis route and heat treatment on crystal structure

    R. R. Shukla, V. Grover, S. K, B. Paul, A. Roy, R. Gupta and A. K. Tyagi, Dalton Trans., 2018, Accepted Manuscript , DOI: 10.1039/C7DT04849A

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