Richard Jarman - Synthesis and characterization of mixed phases in the Ca–Co–O system using the Pechini method

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  Synthesis   and characterization of mixed phases in the Ca–Co–O system using   the Pechini method, H. Tran, T. Mehta, M. Zeller and R.H. Jarman,   Mater. Res. Bull, 48, 2450 (2013).


  The synthesis of mixed phases in the Ca–Co–O system using the   Pechini method was investigated. The

  phases CaCo2O4, Ca3Co4O9 and Ca3Co2O6, which can be expressed in   terms of the molar ratios of the

  binary oxides (CaO:Co2O3) as (1:1), (3:2) and (3:1) respectively,   were obtained in pure form. Powder Xray

  diffraction data showed they are comparable with materials   obtained by conventional solid-state

  synthesis. The mild synthesis conditions of the Pechini method   allowed the evolution of the Ca–Co–O

  phases to be studied as a function of temperature and heating   time. Both variables have a strong

  influence on the composition of the products, indicating that   both kinetic and thermodynamic factors

  play a role, with the former being of more importance at lower   temperatures. The (1:1) phase, previously

  not identified in the phase diagram of the Ca–Co–O system, was   obtained preferentially across the

  composition range below ca. 650 8C. The (3:2) phase was preferred   until ca. 800 8C. At even higher

  temperatures, the (3:1) phase is obtained. The upper thermal   stability limit of mixed phases in the Ca–

  Co–O system increases with the Ca:Co ratio. An updated phase   diagram for the Ca–Co–O system is


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