In situ optical absorption and reflection spectroscopy of doping CsCl crystal with Pb2+ ions

Behaviours of Pb2+ ions during thermal treatments of PbCl2-deposited CsCl crystals have been observed in situ by optical absorption and reflection spectroscopy. In the early stages of the treatments, the Pb2+ ions take part in the formation of Cs4PbCl6 crystallites near the surface of the CsCl crystals. The crystallites exhibit a novel absorption spectrum suggesting that the 6s and 6p states of the Pb2+ ions are strongly localized. On heavy annealing at a high temperature (673 K) followed by a rapid cooling to room temperature, the Pb2+ ions are uniformly dispersed throughout the CsCl crystals, exhibiting the absorption spectrum attributable to isolated Pb2+-ion centres