Morphology and kinetics of polymorphic transformations in K0.965Rb0.035NO3 single crystals

Polymorphic transformations in K 0.965 Rb 0.035 NO 3 single crystals have been investigated by optical microscopy and X-ray diffraction. The equilibrium temperature between modifications II and III of the crystal studied is determined to be T = 452 ± 0.5 K. It is found that polymorphic transformations are of the single crystal ↔ single crystal type and occur with the formation and growth of nuclei of new crystals in matrix ones at II ↔ III transformations. An empirical dependence of the growth rate of modification III on temperature is established in the form ϑ = ϑ = (–0.478Δ T + 0.712Δ T 2 –0.00041Δ T 3 ) × 10 –2 cm/s (Δ T = T tr – T 0 , where T tr is the transformation temperature and T 0 is the equilibrium temperature).