Reaction enthalpies of Cu2ZnSnSe4 synthesis in KI

The phase transitions and chemical reactions in the formation process of Cu2ZnSnSe4 (CZTSe) from CuSe, SnSe, and ZnSe in the presence of KI were studied using the DTA method for the determination of thermal effects. XRD and Raman spectroscopy were performed for the phase analysis in samples after heating them for prolonged time to several degrees of temperatures higher than peak-top temperatures of DTA effects in heating and cooling curves. The chemical pathways of the CZTSe formation before and during the melting of KI were clarified. The reaction enthalpies were determined using pure KI as a substance for the calibration of enthalpy values. In the mixtures, the melting of KI is always accompanied by some dissolution of the precursor compounds and lowering of the melting temperature in comparison with pure KI. The initiator of the process of the partial CZTSe formation at around 400 °C is elemental Se. The CZTSe formation of binary precursors in liquid phase of KI takes place with the experimentally determined enthalpy of −36 ± 2 kJ mol−1. The heat of fusion of formed CZTSe is 4 kJ mol−1 at 788 °C.