Determination of Lattice Parameters of Polytypes in Liquid-Phase-Sintered SiC Using the Rietveld Method

• Published in: Journal of the American Ceramic Society 2004-05, Vol.87 (5), p.943-949
• Main Authors: Hernández-Jiménez, Angel, Ortiz, Angel L., Sánchez-Bajo, Florentino, Guiberteau, Fernando, Cumbrera, Francisco L.
• Format: Article
• Language: English
• Subjects: Applied sciences; Building materials. Ceramics. Glasses; Ceramic industries; Ceramic sintering; Chemical industry and chemicals; Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Hydrides, borides, nitrides, etc., and metalloidal compounds; Inorganic compounds; Materials science; Miscellaneous; Physics; Polymer processing; silicon carbide; sinter/sintering; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; Technical ceramics; X-ray methods
• ISSN: 0002-7820; 1551-2916
• DOI: 10.1111/j.1551-2916.2004.00943.x

Accurate determination of lattice parameters of polytypes in liquid‐phase‐sintered (LPS) SiC by conventional X‐ray powder diffractometry is difficult due to the severe overlap between different Bragg reflections and to the presence of geometrical aberrations. For this reason, results obtained by traditional internal‐standard d‐spacing methods will be in general unrealistic. In this context, the Rietveld method, which is based on the refinement of a structural, profile, and instrumental model, is a more appropriate procedure to determine lattice constants of polytypes in these ceramics. Therefore, in this study we evaluated the accuracy of the results given by the Rietveld method for multiphase mixtures of SiC polytypes, when line broadening is dominated by the crystallite size. The accuracy was found to be remarkable, being sensitive to the number of polytypes but insensitive to the length of the lattice parameters and to the number of geometrical aberrations. In addition, an application to an LPS SiC specimen revealed the usefulness of the Rietveld method to better understand the microstructural evolution during sintering.