Phase diagram and point defect parameters of the system CsBr-TLBr

The phase diagram of the system CsBr-TlBr has been defined through AC conductance determinations at various T and compositions. The experimental data have been worked out through the model of the regular mixtures which seems quite suitable to this system. The same conductivity data allow to evaluate the energy of formation, Ef, and the molar ratio, XO, of the free Schottky defects which have been assumed to be predominant throughout the composition range of the solid solution. A semiempirical method for the a priori evaluation of migration energies and transport numbers of Br -, Tl + and Cs + has been employed to attain this aim. The Efvs. composition plot shows a not expected peculiar trend. The obtained order of magnitude of XO, viz. 10 -4-10 -5, is in agreement with that reported for salts having CsCl type structure.