Experimental investigation and calculation of the phase diagram of the binary system (LiNO₃ + TlNO₃)

Solid–solid and solid–liquid equilibria in the (LiNO₃ + TlNO₃) binary system were investigated under atmospheric pressure, using simultaneous direct and differential thermal analysis (STA/DTA), differential scanning calorimetry (DSC) and X-ray diffraction (XRD) techniques. The (LiNO₃ + TlNO₃) phase diagram exhibits one eutectic reaction at (405 ± 1) K and two plateaus, at (349 ± 1) and (417 ± 1) K, corresponding to TlNO₃ polymorphic transitions. The eutectic transformation enthalpy, measured by DSC technique, is (60 ± 3) kJ kg⁻¹. An optimization of the thermodynamic parameters in the binary system (LiNO₃ + TlNO₃) was performed. The calculated phase diagram and the thermodynamic functions agree well with the experimental data.