Metastability of atomic ordering in lead–strontium nitrate solid solutions

A decrease in the anomalous birefringence of ostensibly cubic crystals of (Pb,Sr)(NO3)2 during annealing between 280–450 °C shows first-order reaction kinetics with Arrhenius-like temperature dependence. The activation energies associated with this process were 111(5) and 359(17) kJ/mol below 370 °C and above 400 °C, respectively. Such behavior agrees with theoretical predictions and confirms that the ordering of cations is the primary cause of the anomalous birefringence.