DETERMINATION OF IMPURITIES IN SIALON BY ICP-AES

Impurities (Ca, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Ti, Y, Zn and Zr) in si alon powder were determined by the following procedure: A sample (0.5 g) was heated with a mixture of hydrofluoric acid (3 ml) and nitric ac id (1 ml) in a Teflon pressure vessel at 170-degrees-C for 16 h. The c ontents of the vessel were transferred into a platinum crucible contai ning phosphoric acid (4 ml) and heated on a hot plate until the opaque appearance of the content changed to a clear-syrupy fluid. The fluid was diluted to 100 ml with water and used for ICP-AES analysis of all impurity elements except K, which was determined by AAS. It was necess ary to match closely the matrix concentrations (H3PO4, Al and/or Y) of the standard solutions with those of sialon sample solutions for the determination of impurities because of interferences of the matrix com ponents. This method was successfully applied to the determination of impurities in commercial sialon samples.