Thermodynamic properties and phase diagram for the system MoO2-TiO2

Thomas Jacob, K. ; Shekhar, Chander ; Waseda, Yoshio (2008) Thermodynamic properties and phase diagram for the system MoO2-TiO2 Journal of the American Ceramic Society, 91 (2). pp. 563-568. ISSN 0002-7820

Full text not available from this repository.

Official URL:

Related URL:


The activity of molybdenum dioxide (MoO2) in the MoO2-TiO2 solid solutions was measured at 1600 K using a solid-state cell incorporating yttria-doped thoria as the electrolyte. For two compositions, the emf was also measured as a function of temperature. The cell was designed such that the emf is directly related to the activity of MoO2 in the solid solution. The results show monotonic variation of activity with composition, suggesting a complete range of solid solutions between the end members and the occurrence of MoO2 with a tetragonal structure at 1600 K. A large positive deviation from Raoult's law was found. Excess Gibbs energy of mixing is an asymmetric function of composition and can be represented by the subregular solution model of Hardy as follows ΔGE(J/mol) = XTiO2X MoO2(19 450XTiO2 + 28 840XMoO2) The temperature dependence of the emf for two compositions is reasonably consistent with ideal entropy of mixing. A miscibility gap is indicated at a lower temperature with the critical point characterized by Tc (K)=1560 and XcTiO2. Recent studies indicate that MoO2 undergoes a transition from a monoclinic to tetragonal structure at 1533 K with a transition entropy of 9.91 J·(mol·K)-1. The solid solubility of TiO2 with rutile structure in MoO2 with a monoclinic structure is negligible. These features give rise to a eutectoid reaction at 1412 K. The topology of the computed phase diagram differs significantly from that suggested by Pejryd.

Item Type:Article
Source:Copyright of this article belongs to American Ceramic Society.
ID Code:13070
Deposited On:11 Nov 2010 06:56
Last Modified:03 Jun 2011 09:08

Repository Staff Only: item control page