Effect of selected impurities on the high temperature mechanical properties of hot-pressed silicon nitride

The compression creep behaviour of silicon nitride ceramics

“…Several studies have shown that the creep strength of HPSN can be increased considerably by minimizing the impurity contents, particularly the CaO levels [13,19,20]. Another possible method of improving the creep resistance of silicon nitride involves the incorporation of a dispersion of silicon carbide particles [5,43].…”

“…No specific conclusions can be drawn from the exact differences in the creep resistance of these materials since the high temperature properties of each type of product are known to vary depending on the impurity levels [9,10,13,19,20] and the detailed fabrication procedures used [9,10,21,22], e.g. the decrease in creep strength associated with the presence of a higher MgO content is evident from the results obtained for the two samples of hot-pressed silicon nitride considered (Figs.…”

Transition metals in photovoltaic-grade ingot-cast multicrystalline silicon: Assessing the role of impurities in silicon nitride crucible lining material

“…Recent neutron activation analysis (NAA) studies revealed metal concentrations in ingot-cast multicrystalline silicon (mc-Si) materials as high as 10 13 -10 16 cm À3 (i.e., in the ppb to ppm range) [1][2][3]. Subsequent studies [4,5] indicated that the majority of metals are present either in (a) metal silicide nanoprecipitates typically o100 nm in diameter, composed of medium-or fast-diffusing metal species, and present in high spatial densities (especially along structural defects), or (b) larger particles up to several microns in size, often in an oxidized chemical state and/or containing multiple slowly diffusing impurity species, present in low spatial densities.…”

High Temperature Mechanical Properties of Polyphase Ceramics Based on Silicon Nitride.

“…His--tor ically, the effect of impurities was observed first. ( 4 4, 45) As clearly demonstrated by Iskoe et al ( 46) , of the major cation impurities found in S1 3N4 , Ca produces the most significan t degradation for material densifled with the aid of MgO. The second compositional effect is that due to changes in the major powder cçnstituents as expressed by the MgO/Si0 2 molar -ra tio (15J for compositions in the Si 3N4-Si0 2 -.MyO system ,.…”