A composition of matter comprises particles each having a substrate being an oxide or other suitable compound of a metal other than titanium or of certain non-metal elements, and a coating on said substrate being a layer of titanium dioxide. A method of forming particles of titania-coated substrate, includes contacting a bed of hydrated particles of an oxide or other suitable compound of a metal other than titanium or of certain non-metal elements with a fluid medium containing flowing titanium tetrachloride, under conditions in which a layer comprising one or more involatile oxychloride or oxide compounds is formed at and below the surface of each of a multiplicity of the particles of the oxide or other suitable compound which thereby provides a substrate for the layer. The oxychloride or oxide compound or compounds are treated to convert the layer to a titania coating on the particles.