Crystal structure and texture of H2S-precipitated cadmium sulfide

Polycrystalline and predominately mixed-phase CdS particles are obtained by H2S precipitation from acidic cadmium solutions with various concentrations of SO42-, ClO4-, NO3-, and/or Cl-. None of the precipitates is free of interstitial (void) space. The roughness of the particle surface increases with the number of crystallites in one particle. Chloride is shown to play an exceptional role in the precipitation: (i) Chloride promotes the formation of hexagonal CdS, while in the presence of the other anions the cubic phase predominates at low supersaturation or anion concentration. The fraction of hexagonal CdS increases with the concentration of anions present in the precipitation media. The higher the complex formation constant between the anion and Cd2+, the stronger this effect proves to be. (ii) Chloride promotes the formation of more particles and inhibits the aggregation of crystallites into one single particle. (iii) Chloride is present in considerable amounts, mainly at grain boundaries inside the particles, while sulfate and perchlorate are adsorbed mainly at the particle surface.