Viscosities of Oxynitride Glass and the Effects on High Temperature Behaviour of Silicon Nitride-Based Ceramics

2005 ◽  
Vol 287 ◽  
pp. 259-264 ◽  
Author(s):  
Stuart Hampshire ◽  
Michael J. Pomeroy
Keyword(s):  
Glass Transition ◽  
Rare Earth ◽  
High Temperature ◽  
Silicon Nitride ◽  
Volume Fraction ◽  
Temperature Behaviour ◽  
Rare Earth Cation ◽  
Intergranular Films ◽  
Oxynitride Glass ◽  
Earth Cation

M-Si-Al-O-N glasses (where M = Y or rare earth cation) are intergranular phases in silicon nitride based ceramics in which the composition and volume fraction of these oxynitride glass phases determine the properties of the material, in particular, high temperature mechanical behaviour. Investigations on oxynitride glass formation and properties have shown that nitrogen increases the glass transition and softening temperatures, viscosity, elastic modulus and hardness. By changing the cation ratios or the type of rare earth cation incorporated, properties such as viscosity can be increased further. This paper provides an overview of oxynitride glasses and outlines the effect of composition on properties such as glass transition temperature and viscosity. These effects have important implications for silicon nitride based ceramics where amorphous intergranular films control high temperature properties such as creep resistance.

Oxynitride Glasses and Their Properties - Implications for High Temperature Performance of Silicon Nitride-Based Ceramics

2006 ◽  
Vol 317-318 ◽  
pp. 419-424 ◽  
Author(s):  
Stuart Hampshire ◽  
Michael J. Pomeroy
Keyword(s):  
Glass Transition ◽  
Rare Earth ◽  
High Temperature ◽  
Silicon Nitride ◽  
Elastic Moduli ◽  
Aluminosilicate Glass ◽  
Temperature Behaviour ◽  
Intergranular Films ◽  
Nitride Ceramics ◽  
Earth Cation

Oxynitirde glasses are found at triple point junctions and as intergranular films in silicon nitride based ceramics. The glass chemistry, particularly the content of modifyer,usually Y or a rare earth (RE) ion, and the volume fractions of these oxynitride glass phases within the ceramic control the properties of silicon nitride, in particular, creep at high temperature. It is known that, as nitrogen substitutes for oxygen in silicate and aluminosilicate glass networks, increases are observed in glass transition and softening temperatures, viscosities (by two to three orders of magnitude), elastic moduli and microhardness. If changes are made to the RE:Si:Al ratios or different rare earth cation are substituted, properties such as viscosity can be increased by a further two to three orders of magnitude. These effects have implications for the high temperature properties of silicon nitride based ceramics, especially creep resistance. This paper provides an overview of oxynitride glasses and outlines the effect of composition on properties such as glass transition temperature and viscosity and discusses the effects on high temperature behaviour of silicon nitride ceramics.

Oxynitride Glasses: Preparation, Properties and Implications for Mechanical Behaviour of Silicon Nitride

2007 ◽  
Vol 554 ◽  
pp. 11-16
Author(s):  
Stuart Hampshire ◽  
Michael J. Pomeroy
Keyword(s):  
Rare Earth ◽  
High Temperature ◽  
Silicon Nitride ◽  
Strong Impact ◽  
Temperature Behaviour ◽  
Intergranular Films ◽  
Liquid Phases ◽  
Earth Cation ◽  
Alumino Silicate ◽  
Si3n4 Ceramics

Oxynitride glasses are found at grain boundaries, i.e. triple point junctions and intergranular films, in silicon nitride based materials as a result of cooling of liquid phases formed by reaction of sintering additives with silicon nitride and silica present on the nitride surface during the densification of the ceramics. The glass chemistry, particularly the content of modifying cation, usually Y or a rare earth (RE) ion, and the volume fractions of these oxynitride glass phases within the ceramic affect the properties of silicon nitride such as fracture toughness and creep at high temperature. As nitrogen substitutes for oxygen in silicate and alumino-silicate glasses, increases are observed in glass transition and softening temperatures, viscosities (by two to three orders of magnitude), elastic moduli and microhardness. If changes are made to the RE:Si:Al ratios or as the size of the rare earth cation decreases, properties such as viscosity can be increased by a further two to three orders of magnitude. These effects have a strong impact on the mechanical properties of silicon nitride based ceramics, especially creep resistance. This paper provides an overview of previous work on oxynitride glasses and outlines the effect of glass composition on their properties and discusses the implications for high temperature behaviour of Si3N4 ceramics.

Oxynitride Glasses and Glass Ceramics

1992 ◽  
Vol 287 ◽  
Author(s):  
Stuart Hampshire
Keyword(s):  
Glass Transition ◽  
High Temperature ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Silicon Nitride ◽  
Grain Boundaries ◽  
Glass Ceramic ◽  
Glass Ceramics ◽  
Heat Treatments ◽  
Oxynitride Glass

Silicon nitride based ceramics contain oxynitride glass phases at the grain boundaries which can impair subsequent high temperature properties. Investigations of bulk glasses in various M-Si-Al-O-N systems have been carried out and it has been shown that up to 15 atomic % N can be incorporated into these oxynitride glasses. Studies have revealed that nitrogen increases the viscosity, hardness and glass transition temperature of the glasses. Heat treatments of the glasses to form crystalline phases have been reported but further improvements are possible if glass-ceramic processes using two-stage heat treatments are introduced. The development of oxynitride glasses and the effects of nitrogen on properties are reviewed and the optimisation of glass-ceramic heat-treatments are reported.

P-type conductive CuYO2phosphor Co-doped with Eu, Tb or Tm rare-earth cation and Ca acceptor cation

2006 ◽  
Vol 203 (11) ◽  
pp. 2723-2728 ◽  
Author(s):  
Nozomu Tsuboi ◽  
Takanobu Hoshino ◽  
Satoshi Kobayashi ◽  
Keizo Kato ◽  
Futao Kaneko
Keyword(s):  
Rare Earth ◽  
Rare Earth Cation ◽  
Earth Cation ◽  
P Type ◽  
Co Doped
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