Densification Behavior, Phase Transition, and Preferred Orientation of Hot-Pressed ZnS Ceramics from Precipitated Nanopowders

In this study, transparent ZnS ceramics were hot pressed from precipitated wurtzite nanopowders. Influences of sintering temperature on wurtzite-to-sphalerite phase transition and densification behavior have been investigated. Maximum sphalerite phase content and highest densification were simultaneously obtained in the sample hot pressed at 900°C with uniaxial pressure of 250 MPa for 2 h, which accounts for the highest transmittance above 55% and 70% in the range 2–5 μm and 5–13 μm, respectively. Preferred orientation of wurtzite grains in [002] direction paralleled to the press direction was also observed, which is supposed to be benefit to transmittance by reducing birefraction and second-phase scattering. Furthermore, second-phase scattering caused by wurtzite grains has been investigated. It is found that fine grains are conducive to hot-pressed ZnS ceramics with high transmittance, especially in the short-wavelength range.