Thermal Stability of Nanocrystalline Zinc Sulfide ZnS

Nanocrystalline zinc sulfide (ZnS) powders are prepared via hydrothermal deposition from aqueous solutions of zinc nitrate and sodium sulfide in the presence of sodium citrate or Trilon B. The average particle sizes of the product ZnS nanopowders ranging from 2 to 9 nm are tuned via varying the batch concentrations of the reagents. Air-annealing of as-prepared ZnS nanopowders at temperatures of 280 to 530°C oxidizes cubic zinc sulfide to hexagonal zinc oxide. The oxidation of the finest-grained zinc sulfide nanopowders having a particle size of 2 nm starts at 280–330°C, while the coarsest-grained nanopowder having a particle size of 9 nm starts to oxidize at 530°C. In the coarsest-grained ZnS powder, the particle size increases as little as from 9 to 12 nm when temperature rises to 530°C, while the finest-grained nanopowders have their particle sizes increase from 2 to 9 nm in response to the same rise in temperature.