morphotropic transition

https://doi.org/10.1351/goldbook.M04032
An abrupt change in the structure of a solid solution with variation in composition.
Source:
PAC, 1994, 66, 577. 'Definitions of terms relating to phase transitions of the solid state (IUPAC Recommendations 1994)' on page 587 (https://doi.org/10.1351/pac199466030577)