“…For SiC‐based ceramics, drying/crystallizing IGFs leads to increased creep resistance at the expense of fracture toughness . IGFs and other types of GB phases (such as monolayers, bilayers, and trilayers) can play critical roles in the erosive wear resistance of Al 2 O 3, the superplasticity of Y 2 O 3 ‐stabilized ZrO 2 , and embrittlement of metals such as W‐Ni, Mo‐Ni, Cu‐Bi, and Ni‐Bi as well as WC‐Co cermet composites . In functional materials, impurity‐based IGFs and presumably other GB phases (complexions) can critically affect the tunable conductivities for ruthenate based thick‐film resistors, non‐linear I‐V characteristics for ZnO‐Bi 2 O 3 ‐based varistors, thermal conductivity of AlN substrates, and critical currents of high T c superconductors .…”