DETERMINATION OF IMPURITIES IN SINTERED S IALON BY THE PRESSURE ACID DECOMPOSITION ICP-AES

A few decomposition methods were examined in order to determine any im purities in sintered sialon samples. Pulverized samples were severely contaminated. A lump (about 0.15 g) of sintered sialon sample was deco mposed with a mixture of 6 mi of hydrofluoric acid and 4 mi of nitric acid in a Teflon pressure vessel at 190 degrees C for 16 h. The obtain ed solution was filtered through a membrane filter (pore size 1.2 mu m ), and the supernatant was diluted to 100 ml with distilled water. The precipitation, consisting of mainly aluminum fluoride and yttrium flu oride, was decomposed with IO mi of sulfuric acid (1+4) in a Teflon pr essure vessele at 230 degrees C for 24 h, and then diluted to 100 mi w ith sulfric acid (1+9). The proposed method was applied to several com mercial samples, and the impurities were determined by inductively cou pled plasma atomic-emission spectrometry. The detection limits of 18 e lements in the sintered samples were in the range of several mu g/g to 0.1 mu g/g, except for Ga (57 mu g/g).