A material comprising powder particles having a core portion comprising a first mixture, and an encasing portion comprising a second mixture, ∘ the first mixture comprises: ∘ at least 50 mol% but less than 100 mol% from one or more of a simple oxide, a double oxide, a triple oxide, an alkali metal halide, an alkaline earth metal halide, or a metal (component B1); and ∘ less than 50 mol% but more than 0 mol% of a non-sublimating electrical insulator (component A1) independently chosen from one or both of: (a) one or more oxide of trivalent or tetravalent metals, or_ (b) one or more salt with binding properties; ∘ the second mixture comprises ∘ at least 50 mol% but less than 100 mol% of a non-sublimating electrical insulator (component A2) independently chosen from one or both of (a) one or more oxide of trivalent or tetravalent metals, or (b) one or more salt with binding properties; and ∘ less than 50 mol% but more than 0 mol% from one or more of a simple oxide, a double oxide, a triple oxide, an alkali metal halide, an alkaline earth metal halide, or a metal (component B2); and wherein component A1 and component B1 have average particle size up to 100 microns; and component A2 and component B2 have average particle size up to 20 microns; wherein the encasing portion at least partially encases the core portion characterized in that ∘ component B1 and component B2 have a coefficient of thermal expansion at least 10 μm/m/K; and in that ∘ the material is free from a spinel and is capable of forming a spinel under thermal spray conditions. ∘ the first mixture comprises: ∘ at least 50 mol% but less than 100 mol% from one or more of a simple oxide, a double oxide, a triple oxide, an alkali metal halide, an alkaline earth metal halide, or a metal (component B1); and ∘ less than 50 mol% but more than 0 mol% of a non-sublimating electrical insulator (component A1) independently chosen from one or both of: (a) one or more oxide of trivalent or tetravalent metals, or_ (b) one or more salt with binding properties; ∘ at least 50 mol% but less than 100 mol% from one or more of a simple oxide, a double oxide, a triple oxide, an alkali metal halide, an alkaline earth metal halide, or a metal (component B1); and ∘ less than 50 mol% but more than 0 mol% of a non-sublimating electrical insulator (component A1) independently chosen from one or both of: (a) one or more oxide of trivalent or tetravalent metals, or_ (b) one or more salt with binding properties; (a) one or more oxide of trivalent or tetravalent metals, or_ (b) one or more salt with binding properties; ∘ the second mixture comprises ∘ at least 50 mol% but less than 100 mol% of a non-sublimating electrical insulator (component A2) independently chosen from one or both of (a) one or more oxide of trivalent or tetravalent metals, or (b) one or more salt with binding properties; and ∘ less than 50 mol% but more than 0 mol% from one or more of a simple oxide, a double oxide, a triple oxide, an alkali metal halide, an alkaline earth metal halide, or a metal (component B2); and wherein component A1 and component B1 have average particle size up to 100 microns; and component A2 and component B2 have average particle size up to 20 microns; wherein the encasing portion at least partially encases the core portion characterized in that ∘ at least 50 mol% but less than 100 mol% of a non-sublimating electrical insulator (component A2) independently chosen from one or both of (a) one or more oxide of trivalent or tetravalent metals, or (b) one or more salt with binding properties; and (a) one or more oxide of trivalent or tetravalent metals, or (b) one or more salt with binding properties; and ∘ less than 50 mol% but more than 0 mol% from one or more of a simple oxide, a double oxide, a triple oxide, an alkali metal halide, an alkaline earth metal halide, or a metal (component B2); and ∘ component B1 and component B2 have a coefficient of thermal expansion at least 10 μm/m/K; and in that ∘ the material is free from a spinel and is capable of forming a spinel under thermal spray conditions.