Low-temperature heat capacity and thermal expansion of synthetic caracolite Na3Pb2(SO4)3Cl

• Тemperature dependence of heat capacity of Na3Pb2(SO4)3Cl has been measured by adiabatic vacuum calorimetry.
• The thermodynamic functions of the Na3Pb2(SO4)3Cl have been determined for the range from T → 0–336 K.
• The character of heterodynamics of structure was detected.
• The high-temperature X-ray diffraction method was used for the determination of thermal expansion coefficients.

In the present work the temperature dependences of trisodium dilead tris(sulfate(VI)) chloride heat capacity have been measured for the first time in the range from 6 to 336 K. The experimental data were used to calculate standard thermodynamic functions, namely the heat capacity Cp°(T), enthalpy H°(T) − H°(0), entropy S°(T) − S°(0) and Gibbs function G°(T) − H°(0), for the range from T → 0–336 K. The differential thermal analysis was applied to measure temperature of incongruent melting of compound under study. The high-temperature X-ray diffraction was used for the determining thermal expansion coefficients.

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