Solidification and thermodynamic parameters of binary faceted organic alloys: Picric acid–Resorcinol system

• Picric acid-Resorcinol gives congruent melting type phase diagram.
• Eutectics are non ideal mixtures.
• Eutectics have faceted morphology.

With increasing interest in low power high speed microelectronic devices, organic based neutron detectors to replace helium and design of low power controlled explosives, thermodynamic and crystal growth parameters of single and binary organic materials have attracted attention significantly. We have studied Solid–liquid phase equilibrium for Picric acid–Resorcinol system, undercooling, crystallization velocity as function of undercooling, and thermodynamic parameters. The phase diagram shows 1:1 congruent melting compound melting at 374.9 K along with two eutectics which melt at 360.4 and 369.3 K. The linear velocity of crystallizations at different undercoolings followed the v=k (ΔT)n equation, where v is the crystallization velocity, ΔT, is the undercooling, k and n are constant. To understand the nature of molten liquid, excess Gibbs free energy, excess entropy, and excess enthalpy have been calculated from the measured values of heat of fusion and specific heat. FT-IR spectral studies indicated the formation of H-bond in the eutectic mixtures. The eutectics and congruent melting compound were investigated by X-ray diffraction technique and scanning electron microscopy. Microstructural studies were made in the presence and absence of impurities.