Synthesis of Sc2O3 nanopowders and fabrication of transparent, two-step sintered Sc2O3 ceramics

Abstract

Synthesis of Sc2O3 nanopowders using a wet chemical approach and fabrication of transparent polycrystalline Sc2O3 ceramics via a two-step sintering procedure (vacuum sintering plus hot isostatic pressing) have been investigated. A hydrated basic sulphate precursor powder [Sc(OH)(3−2x)(SO4)x.nH2O] is synthesised from the scandium sulphate, hexamethylenetetramine and ammonia water solution at room temperature. Phase transformation processes of the precursor upon calcination are studied via differential scanning calorimetry/thermogravimetry, Fourier transform infrared spectroscopy and X-ray diffractometry. Nanocrystalline Sc2O3 powder is obtained by calcining the precursor at 1100°C for 4 h. The resultant Sc2O3 powder is highly pure, ultrafine (12 nm in average size), of narrow particle size distribution and spherical. Hexamethylenetetramine plays an important role in Sc2O3 particle properties. The transparent Sc2O3 ceramics fabricated by two-step sintering have a highly inline transmittance. The two-step sintering mechanism is discussed.