Phosphides in Metallurgy

Amorphous alloys are of particular interest [14-19]. Non-stochiometry or extended homogeniety ranges are found in most of the transition metal phosphides with formulae MjP and M2P. 

FIGURE 8.2 Coordination schemes of P in metal-rich phosphides (a) 9-fold tetrakaidecahedral, (b) 6-fold trigonal prismatic and (c) 8-fold cubical. 

FIGURE 8.3 Structures of metal-rich phosphides (a) FejP, (b) Fej2Zr2Pv, (c) Co4Hf2P3 [83]. Projections on (001) planes. Lines joining metal atoms form a basic trigonal prismatic arrangement around each P atom. Ninefold coordination achieved with an extra 3 metal atoms in every case (shown with broken line for some P). (Adapted from E. Gangleberger, Monatsch. Chem, 99, 556,1968.) 

Palladium phosphide, PdjP, for example, can have any composition in the range PdjPojs- PdsP,, 00 and cobalt phosphide, Co2Pin the range CO175P-CO2.00P These phenomena are believed to be associated with vacant lattice sites where P or metal atoms are missing. Both boron and silicon have appreciable solid solution in some metal phosphides, where random substitution for P atoms occurs (Table 8.6). 

Copper phosphide, CujP, is very hard, dense, brittle and electrically conducting. Its formation in copper and its alloys can profoundly affect their properties. 

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