ChemInform Abstract: Solubility of Aluminum in Rare Earth Nitrogen Melilite Phases.
Abstract
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ChemInform Abstract
The title property is studied with regard to an improvement of the oxidation resistance of N-melilites R2Si3O3N4 (R: Y, rare earths), making it attractive as grain boundary phase in Si3N4-based ceramics. Crystalline phases of sintered Ln2Si3-xAlxO3+xN4-x (Ln: Nd, x: 0, 0.2, 0.6, 0.8, 1.0, 1.2, 1.4, 2.0; Ln: Sm, x: 0.2, 1.0) solid solutions designated as M′ss phases are characterized by XRD, SEM, EDAX, and 27Al and 29Si NMR techniques. The maximum Al solubility limit x = 1 of Nd M′ss phases leading to a terminal composition of Nd2Si2AlO4N3 is similar to that of Sm M′ss phases but higher than that of Y M′ss phases due to the different size of interlayer cations in the tetragonal layered structure. Sm M′ss phases predominantly consist of AlO4 and SiO2N2 units independent on the extent of Al solubility.
