CHARACTERISTICS AND DETERMINATION OF THE INVARIANT REACTIONS IN MULTICOMPONENT SYSTEMS

Characteristics which can be used to determine the type of invariant r eactions in the multicomponent system have been discussed. They are: ( i) the relations among solidus temperatures; (ii) the position of the liquid phase; (iii) the phase present after ''incipient melting'': the number of univariant phase regions can be observed in partially melti ng samples or the solid phases which can occur in partially melting sa mples which originally consist of other solid phases. Several aspects which must be considered in using the above principles: the sensitivit y and accuracy of experimental methods; the solubility of solid phases ; the consistence among invariant reactions are also discussed. An exa mple of using these principles in determination of the invariant react ions in the vicinity of the (Bi,Pb)(2)Sr2Ca2CU3O10-x (2223) phase in t he Bi(Pb)SrCaCuO system is given.