Deposition of porous nano-WO3 coatings with tunable grain shapes by liquid plasma spraying for gas-sensing applications

• Porous nanostructured WO3 coatings were deposited by liquid plasma spray.
• The contours of the nano-sized WO3 grains are tunable.
• Planar WO3 grain showed oriented growth along its (0 0 2) plane.

Porous nanostructured WO3 coatings were deposited by two routes, solution and suspension plasma spraying. The nanostructural characteristics of the coatings were tunable by adjusting the constituents of the starting liquid precursor and spray parameters. Planar or spherical WO3 grains with controllable sizes in nano-scale have been fabricated. Complete formation of spherical WO3 grains was attained during solution plasma spraying. Enhanced heating of the nano-WO3 particles by augmenting plasma power gave rise to oriented WO3 grain growth along (0 0 2) plane. The planar WO3 grains with the dimension of ~50 nm, ~80 nm, and ~700 nm in thickness, width, and length respectively were fabricated by the suspension plasma spraying. The results provide clear insight into potential gas-sensing applications of the porous WO3 coatings.