Analysis of ZrO2 powders by microwave assisted digestion at high pressure and ICP atomic spectrometry

Abstract

Microwave assisted digestion at high pressure was investigated for the dissolution of different ZrO ₂ -based ceramic powders and their subsequent analysis performed by inductively coupled plasma optical emission spectrometry (ICP-OES) and mass spectrometry (ICP-MS). For a fine grain size ZrO ₂ powder (median particle size <1.9 µm) the results were found to well agree with those obtained in the case of conventional digestion at high pressure, decomposition by fusion with NH ₄ HSO ₄ and slurry nebulization ICP-OES. In the case of microwave assisted digestion at high pressure, up to 600 mg of ZrO ₂ could be dissolved within only 60 min, whereas by conventional digestion at high pressure up to 1000 mg ZrO ₂ powder could be dissolved; however, this required a time of 10 h. By fusion with NH ₄ HSO ₄ it was not possible to dissolve all of the ceramic powders investigated completely. For all investigated elements excepted for B and Si, recoveries of 100% were obtained within the level of experimental error 3-13%. Detection limits, in the case of ZrO ₂ powders with high concentrations of Hf, Na and Y, were found to range from 0.03 µg g ^–1 for Mg, when applying conventional digestion at high pressure, over 0.4 µg g ^–1 for Fe, in the case of microwave assisted digestion at high pressure, to 92 µg g ^–1 for Na in the case of slurry nebulization ICP-OES and 114 µg g ^–1 in the case of Y subsequent to decomposition by fusion. The results of analysis subsequent to the different dissolution methods and those obtained with slurry nebulization ICP-OES agreed well for the elements Cr, Fe, Hf, Mg, Na, Ti and Y. With quadrupole based inductively coupled plasma mass spectrometry Na could be determined at the 600 µg g ^–1 level and the results agreed well with those obtained by ICP-OES, whereas for Al, Cr, Cu, Fe, Mg, Mn and Ni spectral interferences were found to hamper analyses. For Li, as well as for Ce, La, Pr and Th, it could be shown that the impurity levels in the samples analyzed were below 2 and 1 µg g ^–1 , respectively.