Structures of plasma-sprayed Sm2Zr2O7 coatings have been examined by transmission electron microscopy. An order-disorder transition has taken place during the plasma spraying at temperatures around 10(4) K. However, short-range ordering has been observed in the as-sprayed coating. The disappearance of characteristic diffraction resulting from ordering of the oxygen sublattice suggests a cation-ordered while anion-disordered pyrochlore structure. Some ordered structures either deformed or showed different ordering at cation sites. Long-range ordering in which both cations and anions are ordered has been achieved after heat treatment at 1500 degrees C for 20 h, which is characterized by the submicron-sized ordered domains separated by the antiphase boundaries. (C) 2010 Elsevier B.V. All rights reserved.