The Preparation and Nonstoichiometry of Samarium Hexaboride

Abstract

Samarium hexaboride was prepared by the borothermal reaction; 2 Sm2O3+(6+4x)B=4 SmBx+3 B2O2. The residual oxygen content amounted to less than 0.03 w/o under optimum reaction conditions heating at 1650°C for 2 hr under a high vacuum. It was found by X-ray intensity and density measurements that the samarium hexaboride stayed stable over a large nonstoichiometric region from Sm0.68B6 to SmB6. These extensive nonstoichiometric properties of samarium hexaboride can be explained in terms of the required electron numbers of the SmB6 network in hexaboride.