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Journal of Materials Science

, Volume 14, Issue 2, pp 450–454 | Cite as

Order-disorder phenomena in oxides with rock salt structures: the system Li2TiO3-Mg0

  • M. Castellanos
  • A. R. West
Papers

Abstract

Li2TiO3, which belongs to the family of rock salt superstructure phases, undergoes an order-disorder phase transition at 1213° C. It forms solid solutions with MgO and the temperature of the order-disorder change falls increasingly rapidly with increasing MgO content; the ordered solid solutions could not be prepared beyond ∼40 mol % MgO. Up to ∼20% MgO, the transition may be observed as a DTA heat effect and is probably first order. At ≳25% MgO the transition is second order; no DTA heat effect occurs and, by X-ray diffraction, the order-disorder change occurs, reversibly and continuously, over a range of several hundred ° C. For 25% MgO, the disorder, δ, is given by δ=exp[−m(TcT)] whereTc is the critical temperature, above which only short range order exists, andm is a constant. The order, δ, is determined from the relative intensity of the (0 0 2) superstructure reflection. The mechanisms of the order-disorder processes are discussed and a method of studying the kinetics is indicated. It is likely that many other oxide phases which have rock salt superstructures will exhibit order-disorder phenomena at high temperatures.

Keywords

Oxide Phase Transition Solid Solution Relative Intensity Critical Temperature 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Chapman and Hall Ltd. 1979

Authors and Affiliations

  • M. Castellanos
    • 1
  • A. R. West
    • 1
  1. 1.División de Estudios Superiores, Facultad de QuímicaUniversidad Nacional Autónoma de MéxicoMéxico 20, D.F.

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