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Activity of $TiO_2$ in the system $ZrO_2-TiO_2$ and Gibbs energy of formation of $ZrTiO_4$

Jacob, KT and Saji, VS and Waseda, Y (2006) Activity of $TiO_2$ in the system $ZrO_2-TiO_2$ and Gibbs energy of formation of $ZrTiO_4$. In: High Temperature Materials and Processes, 25 (4). pp. 203-208.

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Abstract

The activity of $TiO_2$ in single and two-phase regions of the system $ZrO_2-TiO_2$ has been measured using solid state cells based on yttria-doped thoria (YDT) as the solid electrolyte at 1373 K. The cells used can be represented as: Pt, $Ti_{0.07}Pt_{0.93} + Zr_{1-x}Ti_xO_2/YDT/TiO_2$ + $Ti_{0.07}Pt_{0.93}, Pt Pt, Ti_{0.07}Pt_{0.93} + Zr_{1-x}Ti_xO_2 + ZrTiO_4/YDT/TiO_2 + Ti_{0.07}Pt_{0.93}$, Pt In each cell the composition of Pt-Ti alloy was identical at both electrodes. The emf of the cell is therefore directly related to the activity of $TiO_2$ in oxide phase or oxide phase mixture: $\alpha_{TiO2}$ = exp (-4FE/RT). The activity coefficient of $TiO_2$ in the zirconia-rich solid solution with monoclinic structure (0.02 greater than or equal $X_{TiO2}$ greater than or equal 0) can be expressed as: In $\gamma_(TiO2)$ = 3.145 $(1-X_{TiO2})^2-0.338$ In the zirconia-rich solid solution with tetragonal structure $(0.085 >= X_{TiO2} >= 0.03)$, the activity coefficient is given by: In $\nu_(TiO2)$ (+/- 0.012) = 2.354 $(1-X_{TiO2})^2+0.064$. The standard Gibbs energy of formation of $ZrTiO_4$ is -5650 (+/- 200) J/mol at 1373 K.

Item Type: Journal Article Copyright of this article belongs to Freund and Pettman Publishers. Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy) 27 Jul 2007 24 Jan 2012 09:11 http://eprints.iisc.ernet.in/id/eprint/11440