An article that is particularly well suited for use as a gas turbine engine component has a metallic substrate and a ceramic thermal barrier layer including a mixed metal oxide system comprising a compound selected from the group consisting of (i) a lanthanum aluminate and (ii) a calcium zirconate, the calcium in which is partially replaced by at least one calcium-substitute element, such as strontium (Sr) or barium (Ba). In addition, the lanthanum in the lanthanum aluminate can be partially replaced by a lanthanum-substitute element from the lanthanide group, particularly gadolinium (Gd). A process for producing such an article comprises providing a pre-reacted mixed metal oxide system as described above and applying it to the substrate by plasma spraying or an evaporation coating process.