Synthesis and rapid sintering of dense SrA(O,N)3 (A = Mo, W) oxynitride ceramics.

SrMo(O,N) 3 and SrW(O,N) 3 oxynitride powders were synthesized via a solvothermal route followed by ammonolysis. Their rapid densification by spark plasma sintering with a heating rate of 300–400 °C/min under a uniaxial pressure of 100 MPa yielded dense monoliths. The lowest open porosity achieved was 0 vol% for SrMo(O,N) 3 and 7.6 vol% for SrW(O,N) 3 . The compacted monoliths were characterized by elemental analysis, electron microscopy (SEM, TEM) coupled with energy dispersive X-ray spectroscopy (EDX), as well as X-ray diffraction (XRD). Rietveld refinement of the XRD patterns revealed in the case of the compacted SrMo(O,N) 3 the formation of small amount of ternary oxides (Sr 3 Mo 2 O 7 /SrMoO 4 /Sr 3 MoO 6 ), molybdenum nitride (Mo 2 N), as well as metallic Mo. On the contrary, SrW(O,N) 3 exhibited significant decomposition after consolidation, with SrWO 4 /Sr 3 WO 6 being main components beside SrMo(O,N) 3 , accompanied by tungsten nitride (WN) and metallic W. Thus, rapid SPS enables the densification of oxynitrides with high density and acceptable purity that were hardly achieved earlier. [ABSTRACT FROM AUTHOR]