Surface compositions of hexaborides at high temperatures

摘要

The surface compositions of (La,M) B6hyphen;type hexaborides are investigated at high temperatures using Auger electron spectroscopy. Above 1000thinsp;deg;C, La atoms become more enriched in the surface layer than in the bulk. Surface composition approaches that of LaB6above 1400thinsp;deg;C. Above 1400thinsp;deg;C, the hexaboride surface maintains constant composition during longhyphen;term operation. The surface layer, in which La is more enriched than other metals, is estimated to be 2 or 3 nm thick. This enrichment may be due to the fact that the metals of higher vapor pressures evaporate faster than lanthanum.