A DIFFERENTIAL THERMAL-ANALYSIS CELL SUITABLE FOR SYSTEMS WITH VAPOR-PRESSURES EXCEEDING AMBIENT

In this paper we present a simple differential thermal analysis cell d esigned for measurements in corrosive and volatile salt systems with v apour pressures exceeding ambient pressure. The DTA assembly consists of a sealed platinum capsule, made from a cylindrical Pt tube, welded to a Pt/Pt10%Rh thermocouple for measuring the temperature of the samp le. The differential temperature is obtained by using a reference Pt/P t10%Rh thermocouple for recording the furnace temperature. A reference cell used in conventional DTA assemblies is not necessary in the pres ent set-up due to the small total heat capacity of the DTA assembly re lative to the heat capacity of the furnace environments. Our simple DT A cell has been applied successfully to determine the phase diagrams o f several binary and ternary ZrF4-based systems in the temperature reg ion 200-1200 degrees C. The triple point of pure ZrF4, a compound whic h sublimes at ambient pressure, has also been obtained by the present method.