Vaporization thermodynamics and heat capacities of Ti5Ge3 and Ti6Ge5

Abstract Thermodynamic stabilities of titanium germanides Ti 5 Ge 3 and Ti 6 Ge 5 have been studied by means of high-temperature Knudsen effusion mass spectrometry (KEMS) and differential scanning calorimetry (DSC). Thermodynamic activities of Ti and Ge have been measured over the two-phase mixtures of Ti 5 Ge 3 +Ti 6 Ge 5 in a temperature range of ca. 1680–1880 K by direct comparison with solid Ti and liquid Ge metals. The standard free energies of formation of Ti 5 Ge 3 and Ti 6 Ge 5 at high temperature were determined from the activity data. Heat capacities of Ti 5 Ge 3 and Ti 6 Ge 5 were measured by DSC in the temperature region 300–700 K. Standard enthalpies of formation of Ti 5 Ge 3 and Ti 6 Ge 5 at 298 K were calculated by the third-law method with the use of estimated absolute entropy and high-temperature heat capacity data. The results obtained are: 1 8 Ti 5 Ge 3 , −69.8±5 kJ; 1 11 Ti 6 Ge 5 , −70.1±5 kJ. The results obtained in this work are compared with previous estimates and measurements.