Determination of impurities in sintered sialon by the pressure acid decomposition/ICP-AES.

A few decomposition methods were examined in order to determine any impurities in sintered sialon samples. Pulverized samples were severely contaminated. A lump (about 0.15 g) of sintered sialon sample was decomposed 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 obtained 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 fluoride, was decomposed with IO mi of sulfuric acid (1+4) in a Teflon pressure vessele at 230 degrees C for 24 h, and then diluted to 100 mi with sulfric acid (1+9). The proposed method was applied to several commercial samples, and the impurities were determined by inductively coupled plasma atomic-emission spectrometry. The detection limits of 18 elements 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).