Synthesis of Sc 2 O 3 nanopowders and fabrication of transparent,two-step sintered Sc 2 O 3 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.