难熔化合物,即一类熔点很高的金属化合物(例如碳化铪和碳化钽的熔点已高达～4000℃)。凡周期表中第一族以外的所有2—7列的脆性重金属元素和过渡元素,以及镧系元素和锕系元素,都是难熔化合物的金属组分;甚至B,N,o,Si,P,S等,也是难熔化合物的非金属组分。由这些元素构成的化合物,可以分成两类:其一为类金属化合物,例如碳化物、氮化物、硼化物、磷化物和硫化物等;其二为非金属化合物,例如碳 Refractory compounds, namely a class of very high melting point metal compounds (for example, hafnium carbide and tantalum carbide melting point up to ~ 4000 ℃). All of the brittle heavy metals and transitional elements 2-7 of the Periodic Table, as well as lanthanides and actinides, are metal components of refractory compounds; and even B, N, O, Si, P, S, etc., but also non-metallic refractory compounds. The compounds composed of these elements can be classified into two types: one is a metalloid compound such as a carbide, a nitride, a boride, a phosphide and a sulfide, and the other is a non-metal compound such as carbon