Effect of synthesis temperature on the crystal structure of nano-sized CdS spheres synthesized by Ultrasonic assisted Hydrothermal method

Among the II-VI semiconductors, CdS is one of the most important wide gapsemiconductors with a ΔEg∼2.5 eV for the bulk hexagonal wurtzite phase. Many researchers have carried out studies on CdS because it has numerous applications; for example, as a photocatalyst, solar cells and light-emitting diodes [1], piezoelectric[2], optoelectronic [3]. In the present study, nano-sized CdS spheres were synthesized by hydrothermal reactions between Cd(NO3)2.4H2O and CH4N2S at a constant stoichiometric 1:2 Cd:S molar ratio. Influence of synthesis temperature (120,150,180˚C) was examined for the synthesis of the target. The synthesized nanomaterials were characterized by PXRD and FESEM techniques. Fig.1 shows the PXRD patterns of the obtained samples when the solvent was water and the reaction time was 48h. The PXRD data indicated that the nanomaterials were crystallized well in a hexagonal crystal system with the space group P63mc. The figure shows that when the reaction temperature was 120˚C, there was an obvious impurity cubic CdS peak position in the mixture. However, with increase the reaction time to 150 and then 180˚C, the impurity peak was disappeared. Fig.2 shows the FESEM images of samples. The images show that when the reaction time was 48h, increasing the reaction temperature has no significant effect on the morphology of the targets. The data show that the material is composed of particle and also sphere structures. It is obvious from the images that the reaction temperature 150 ˚C, produces material with almost particle morphology. However, when the reaction temperature was 120 and 180 ˚C, the morphology of the targets is large size sphere.