High-Temperature Properties of Silicon Nitride with Lu-Si-O-N Grain Boundary Phases

High-temperature properties of silicon nitride ceramics with Lu-silicon-oxynitride grain boundary phases were investigated. Si3N4 powder with 1.2 mol% (SN12) and 4.8 mol% (SN48) of Lu2O3 were gas-pressure hot-pressed at 1950°C for 2 h under 20 MPa in 1 MPa N2. SN12 consisted of elongated β-Si3N4 and a secondary phase, Lu4Si2O7N2, whilst SN48 consisted of elongated β-Si3N4 and Lu4Si2O7N2 + Lu2SiO5. At 1500°C and 1600°C, the stress-strain curve of SN48 was nonlinear, whilst that of SN12 was linear, indicating that SN12 broke as a brittle fracture at these temperatures. SN12 had excellent oxidation resistance and weight gain during the oxidation at 1500°C for 1000 h was 4 g/m2. Creep lifetime of SN12 at 1500°C under tensile stress of 137 MPa exceeded 1678.5 h.

[1]  T. Nishimura,et al.  Phase Relationships in the Si3N4–SiO2–Lu2O3 System , 2004 .

[2]  S. Guo,et al.  Hot‐Pressed Silicon Nitride with Lu2O3 Additives: Oxidation and Its Effect on Strength , 2003 .

[3]  S. Guo,et al.  Microstructural characterization and high-temperature strength of hot-pressed silicon nitride ceramics with Lu2O3 additives , 2003 .

[4]  S. Guo,et al.  Hot-pressed silicon nitride ceramics with Lu2O3 additives: elastic moduli and fracture toughness , 2003 .

[5]  S. Guo,et al.  Oxidation behaviour and strength degradation of a Yb2O3−SiO2−doped hot-pressed silicon nitride between 1200 and 1500°C , 2002 .

[6]  N. Hirosaki,et al.  Tensile creep behavior of a ytterbium silicon oxynitride–silicon nitride ceramic , 2002 .

[7]  N. Hirosaki,et al.  Creep and stress-rupture behavior of Y2O3–Nd2O3-doped silicon nitrides with different additive contents , 2002 .

[8]  S. Guo,et al.  Improvement of high-temperature strength of hot-pressed sintering silicon nitride with Lu2O3 addition , 2001 .

[9]  Heon-Jin Choi,et al.  High temperature strength and oxidation behaviour of hot-pressed silicon nitride-disilicate ceramics , 1997 .

[10]  T. Nishimura,et al.  High temperature strength of silicon nitride ceramics with ytterbium silicon oxynitride , 1997 .

[11]  David R. Clarke,et al.  High-alumina tailored nuclear waste ceramics , 1981 .

[12]  R. D. Shannon.  Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides , 1976 .

[13]  G. Gazza.  Hot-Pressed Si3N4 , 1973 .