Thermodynamic properties of synthetic turkestanite KNaCaTh(Si8O20)

• Тemperature dependence of heat capacity of KNaCaTh(Si8O20) has been measured by precision adiabatic vacuum calorimetry.
• The thermodynamic functions of the KNaCaTh(Si8O20) have been determined for the range from T → 0 to 347 K.
• The character of heterodynamics of structure was detected.
• The incongruent melting point of KNaCaTh(Si8O20) was determined by differential scanning calorimetry.

In the present work, the temperature dependence of heat capacity of KNaCaTh(Si8O20) has been measured for the first time within the range from T = 6 K to T = 347 K by precision adiabatic vacuum calorimetry. The experimental values 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 K to 347 K. The value of the fractal dimension D in the function of multifractal generalization of Debye’s theory of the heat capacity of solids was estimated and the character of heterodynamics of structure was detected. The incongruent melting point of KNaCaTh(Si8O20) was determined by differential scanning calorimetry.

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