Abstract: A method of producing a composite plasma spray coating using simultaneous feeding of powder and solution precursor feedstock in a plasma spray gun is disclosed, comprising the steps of a) spraying a powder feedstock comprising micron sized particles into a plasma spray plume; and b) spraying a liquid feedstock comprising liquid precursor solution into the plasma spray plume, wherein the spraying of the powder feedstock and spraying of the liquid feedstock are independently controllable. The method allows control of coating composition and microstructure to deposit nanostructured and microstructured layers either sequentially to form layered coatings, or simultaneously to form either composite coatings or continuously gradient coatings to address diverse applications. Thermal barrier coatings produced using the new method have demonstrated twice the life compared to conventional air plasma sprayed coatings.