Effect of the microstructures of yttria ceramics on their plasma corrosion behavior

Abstract

To demonstrate the relation between the microstructure of ceramics and their plasma corrosion behavior, sintered yttria (Y2O3) ceramics with various grain sizes and porosities were fabricated under various sintering conditions, and the effect of the microstructures of the Y2O3 ceramics on their plasma corrosion behavior was investigated. The Y2O3 samples were investigated by inductively coupled plasma reactive ion etching using fluorine plasma. After plasma exposure, the plasma corrosion depth and surface roughness (Sa) values of the materials were measured using a laser scanning microscope. The surface microstructures after plasma corrosion were observed by scanning electron microscopy. It was found that the plasma depth showed an almost linear change with plasma exposure time, and all the original surfaces of the samples were corroded by over 0.7 μm during plasma exposure for 60 min. The Sa values of the Y2O3 samples as a result of plasma exposure were significantly different in that although the Sa values of low-density Y2O3 samples increased with an increase in the plasma exposure time, the values of their high-density counterparts did not change and the initial surface roughness was maintained. The fluorine plasma was found to homogeneously corrode the surfaces of the sintered Y2O3 ceramics, regardless of their grain boundaries or grain sizes. However, when internal pores were present in the samples, these internal pores were selectively corroded from their edges, becoming crater-like plasma corrosion marks. Overall, a high-density Y2O3 ceramic was found, which retained its initial surface roughness regardless of plasma exposure time, with an ideal microstructure for use as a plasma-resistant ceramic material that can be used as the inner ceramic components in the plasma etching equipment.