INVESTIGATION OF THE LANTHANUM HEXABORIDE OBTAINING PROCESSES BY THE METHOD OF BOROTHERMAL REDUCTION

Abstract

Obtaining new ceramic and composite materials is associated with a number of difficulties, the key of which is the lack of pure initial refractory components. The presence of impurities in the powders available on the market (such as oxygen, iron, carbon, etc.) has a negative impact on the performance characteristics of the resulting materials and products from them. The paper presents the results of experimental studies on the lanthanum hexaboride powder synthesis by boron thermal reduction of lanthanum oxide in a vacuum furnace and a spark plasma sintering unit. The analysis of the obtained results showed that when the content of excess boron in the mixture is 20 wt. % by heat treatment in a vacuum furnace, a single-phase powder of lanthanum hexaboride was obtained at temperatures of 1800 – 1900 ?C. The use of the spark plasma sintering method, however, makes it possible to reduce the temperature of synthesis of a single-phase powder of lanthanum hexaboride to 1700 and 1600 ?C with an excess boron content in the charge of 10 and 20 wt. %, respectively. It is also shown that these powders are characterized by a more uniform cubic structure of lanthanum hexaboride, reflecting its crystalline structure, due to the suppression of the grain recrystallization process by reducing the temperature and time of the technological process.