Molybdenum and tungsten interaction with rare earth metals and boron

The systems Y-[Mo, W]-B (10000C) and [La, Ce]-[Mo, W]-B (800, 6000C) were studied by methods of X-ray crystallographic analysis, and the corresponding isothermal dimensions were plotted. The existence of the ternary compounds YMoB4 and YWB4 with a structure of the YCrB4 type was confirmed. In the Ce-Mo-B system, a ternary compound of unknown structure (approximately CeMoB3), formed only after annealing at 8000C, was found. In the Ce-Mo-B system, the following equilibria were found: CeB6-MoB4, Mo2B5, MoB; CeMoB3-CeB4, Ce, MoB; MoB-CeB4, Ce; Mo2B-Ce. In the Ce-W-B system, there are the following equilibria: CeB6-WB4, W2B5, WB; CeB4-WB, W2B; Ce-W2B. A comparative description is given of the ternary systems [Y, La, Ce]-[Mo, W]-B and the conditions for the formation of compounds with a structure of the YCrB4 type are discussed. (author)