Crescimento e caracterização de nanocristais de Bi2S3 dopados com cromo em matrizes vítreas

Abstract

This study aims at presenting the results of the synthesis of nanocrystals semiconductors of Bi2S3 and nanocrystals magnetic semiconductors has been diluted in Bi2-xCrxS3 in vitreous matrices. To confirm the formation and growth of these nanocrystals, were performed experimental measurements of x-ray diffraction, transmission electron microscopy (TEM) and Uv-Vis Spectroscopy. The images of transmission electron microscopy obtained for the array of vitreous composition 45SiO2.30Na2CO3.5Al2O3.20B2O3 (mol%) + 2 Bi2O3(%wt) + 2S (%wt) + xCr (%wt (Bi), confirmed the growth of nanocrystals of Bi2-xCrxS3 and the identification of the size of these nanocrystals. There is also an increase in the distance interplanar with increase in the concentration of ions Cr3+ in the sample, modifying the spacing between the crystal planes of the crystal structure for Bi2S3 . The Bi2-xCrxS3 peaks of diffraction grating of nanocrystals of Bi2S3 moves to lower angles with the increase of the concentration of Cr3+ due to the change of the parameter of the crystal structure characteristics of Bi2S3, giving strong evidence of the incorporation of these ions in the crystal structure of nanocrystals of Bi2S3. The spectra of Uv-Vis show two bands of absorption conferred the ion Cr3+ in octahedral sites, according to the crystal field Theory. These bands of absorption are moving to higher wave lengths, lower energies, with the increase in the concentration of ions Cr3+ and with heat treatment, indicating growth of nanocrystals and the incorporation of these ions in the crystal structure. The transitions d-d observed were associated with the lines of correlation of diagram of Tanabe Sugano allowing to calculate the values of Δo and B that make the transitions seen fit to the diagram.