Lead iodide crystals prepared under stoichiometric and nonstoichiometric conditions

We report on the influence of stoichiometric and nonstoichiometric conditions on the electrical and optical properties. The samples with the excess of iodine, under stoichiometric conditions and with the lead excess were prepared. Direct synthesis of the elements lead and iodine was used for preparing lead iodide and purified by zone melting. Further, we report the influence of the admixture of rare earth elements, rare earth iodides and other elements on the properties of synthesised PbI2 material. Prepared materials were characterized by measurement of electrical resistivity and low-temperature photoluminescence (PL) spectra and in this way the influence of nonstoichiometric variancy and doping was compared. High resistivity materials were attained and the best results of resistivity were obtained for stoichiometric material and the admixture of Gd, Tm, HoI3 and Ge. The PL spectra of samples are fairly similar and no systematic dependence was found. For Ho and Tm doping a considerable narrowing of donor related PL band was observed in good correlation with highest resistivities of these samples.