Purification and Crystal Growth of the Bismuth (III) Iodide-influence of Trace Impurities on the Crystal Quality

Abstract

This work describes the experimental procedure of purification and preparation of BiI 3 crystals by Repeated Vertical Bridgman technique, aiming a future application of this semiconductor crystal as a room temperature radiation detector. The BiI 3 powder used as raw material was purified three times and, at each purification, the crystal was evaluated by systematic measurements of the reduction of the impurities, crystalline structure, stoichiometry and surface morphology. The reduction of the trace metal impurities in the BiI 3 , at each purification, was analyzed by Instrumental Neutron Activation Analysis (INAA), in order to evaluate the efficiency of the purification technique established in this work. It was demonstrated that the Repeated Bridgman technique is effective to reduce the concentration of many impurities in BiI 3 , such as Ag, As, Br, Cr, K, Mo, Na and Sb. The crystalline structure of the BiI 3 crystal purified twice and three times was similar to BiI 3 pattern. However, for BiI 3 powder and purified once, an intensity contribution of the BiOI was observed in the diffractograms. Improvement in the stoichiometric ratio was observed at each purification step, as well as the crystal surface morphology.

Aplicações da Análise por Ativação Neutrônica para Determinações Multielementares em Diferentes Materiais

“…O Laboratório de crescimento e purificação de cristais -IPEN desenvolveu uma metodologia para a preparação dos sais de: PbI 2 , TlBr e BiI 3 para o crescimento dos cristais, visando sua aplicação como detector de radiação. Esta metodologia consistiu de: 1) purificação dos sais comerciais (PbI 2 , TlBr e BiI 3 ) com graus de pureza de 99 a 99,999% de pureza por meio da técnica de "purificação por refinamento zonal"; 2) avaliação da eficiência de purificação por meio da determinação de impurezas presentes nos materiais por INAA [9][10][11][12][13][14]. Verificou-se que INAA permitiu verificar significante redução de impurezas, de acordo com os números de passos de purificação.…”