A sinple method for synthesis of acicular B-Si3N4 seed crystals

GOULD; D. A; QUINLAN, M; ALBANO, M. P; GARRIDO, L. B.; GENOVA, L; PLUCKNETT,K

CERAMICS INTERNATIONAL

Elsevier

Lugar: Irlanda; Año: 2008

0272-8842

Acicular silicon nitride (b-Si3N4) seed crystals have been synthesized using a moderately low temperature heat-treatment process, with the aid of a low volume fraction of multiple sintering aids (i.e. MgO and CaO, in combination with either Y2O3 or Nd2O3). The effects of the heat-treatment cycle and the additive composition on the a- to b-Si3N4 phase transformation were examined, for both cold-isostatically pressed pellets and simple packed powder. For the case of the packed powder, full transformation was achievable following heat-treatment at 1625ºC for four hours, in ~0.1 MPa nitrogen. The use of multiple oxide additives allows seed liberation from the heat-treated materials using a simple dilute HF soak at room temperature. The resulting b-Si3N4 seed crystals exhibit a narrow size distribution, with mean aspect ratios of ~4:1.