A-15相是一类特殊的A_3B型化合物,其中A元素必须是ⅣA,ⅤA,ⅥA族过渡元素。电子密度e/a和组元A,B的半径比r_A/r_B是决定A-15相性质的两个重要因素。Matthias首先注意到e/a对A-15相超导临界温度T_c的影响。当e/a=4.7和6.5时,T_c分布的包络线上出现两个峰。但也有不少A-15相虽然具有最适宜的e/a值,T_c仍很低,甚至根本没有超导性。Hartsough总结了影响A-15相形成的因素,认为r_A/r_B= A-15 phase is a special type of A_3B compounds, elements A must be IVA, VA and VIA transition elements. The electron density e / a and the ratio of the radii of elements A and B, r_A / r_B, are two important factors that determine the nature of A-15 phase. Matthias first noted the effect of e / a on the A-15 phase superconducting critical temperature T_c. When e / a = 4.7 and 6.5, two peaks appear on the envelope of T_c distribution. However, many A-15 phases, although having the most suitable e / a values, have low T_c or even no superconductivity. Hartsough summed up the factors that affect the formation of A-15, that r_A / r_B =