phase domain

https://doi.org/10.1351/goldbook.PT07286
Region of a material that is uniform in chemical composition and physical state.
Notes:
  1. A phase in a multiphase material can form domains differing in size.
  2. The term 'domain' may be qualified by the adjective microscopic or nanoscopic or the prefix @M03894@- or @N04082@- according to the size of the linear dimensions of the domain.
  3. The prefixes @M03894@-, and @N04082@- are frequently incorrectly used to qualify the term 'phase' instead of the term 'domain'; hence, 'microphase domain', and 'nanophase domain' are often used. The correct terminology that should be used is phase microdomain and phase nanodomain.
Source:
PAC, 2004, 76, 1985. 'Definition of terms related to polymer blends, composites, and multiphase polymeric materials (IUPAC Recommendations 2004)' on page 2001 (https://doi.org/10.1351/pac200476111985)