BRAGG-WILLIAMS ANALYSIS APPLIED TO SOME PHASE-DIAGRAMS INVOLVING MNIII2VI4 COMPOUNDS

The T(z) diagrams were determined by differential thermal analysis (DT A) for a number of alloy systems of the forms II1-zMnzIII2VI4 and I2(1 -x)MnzIII2VI4, each of which showed two or more ordering transitions i nvolving the Mn atoms. Each type of ordering transition has been theor etically investigated in terms of a Bragg-Williams type of analysis (B WA). It was found that the BWA predictions showed good agreement with the DTA data, in particular the variation of the critical temperature T-c with composition z and the ratio of continuous to discontinuous co mponents of each of the ordering transitions. (C) 1997 Elsevier Scienc e S.A.