Components having an environmental barrier coating and a sintered layer overlying the environmental barrier coating, the sintered layer defining an outer surface having a lower surface roughness than the environmental barrier coating. The sintered layer is formed from a slurry applied to and then sintered on the environmental barrier coating. The sintered layer comprises a primary material, at least one sintering aid dissolved in the primary material, and optionally a secondary material. The sintering aid contains at least one doping composition. The primary material is a rare earth disilicate or a rare earth monosilicate and is doped with the doping composition so as to be either a doped rare earth disilicate or a doped rare earth monosilicate. The optional secondary material is a reaction product of the primary material and any of the sintering aid not dissolved in the primary material.