# Thermodynamic evidence for order-disorder transition in $NiTiO_3$

Jacob, KT and Saji, VS and Reddy, SNS (2007) Thermodynamic evidence for order-disorder transition in $NiTiO_3$. In: Journal of Chemical Thermodynamics, 39 (2). pp. 230-235.

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## Abstract

The standard Gibbs free energy of formation of $NiTiO_3$ from its component oxides NiO with rock salt structure and $TiO_2$ with rutile structure $\Delta_f G^o_{(ox)} (NiTiO_3)$ has been measured over a wide temperature range (900 to 1700) K employing the solid-state electrochemical cell: $Pt|Ni+NiTiO_3+TiO_2||(Y_2O_3)ZrO_2||Ni+NiO|Pt$ The measured EMF, which is directly related to the Gibbs free energy of formation of $NiTiO_3$ from component oxides, can be represented by two linear segments; E\pm 0.38/(mV)=63.48-0.01264 (T/K), in the range T = (900 to 1565) K, and E\pm 0.35/(mV)=-16.21-0.03831 (T/K) in the range T = (1565 to 1700) K. The change in slope at T = 1565 K is related to the transition from ordered ilmenite structure of $NiTiO_3$ with space group $R\bar{3}$ to a kind of disordered corundum structure with space group, $R\bar{3}c$ involving essentially an order–disorder transition on the cationic sublattice. The new measurements help to resolve discrepancies in thermodynamic data on $NiTiO_3$ reported in the literature.

Item Type: Journal Article Copyright of this article belongs to Elsevier. Phase transition;EMF technique;Gibbs free energy;Enthalpy; Entropy Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy) Satish MV 03 Apr 2007 19 Sep 2010 04:37 http://eprints.iisc.ac.in/id/eprint/10614