In the thermal spray process, particulate materials can be melted by plasma atmosphere due to its high local temperature from 8700 °C to 15,000 °C. Therefore, the material powders turn into droplets after being melted by injection into the hot flame. Molten droplets are accelerated toward a substrate and form the splats which quickly solidify; finally, the film is formed by pile-up splats. Splat morphology and post treatment can determine the microstructure, mechanical and physical properties of the coating. In this study, BaTiO 3 films were deposited onto a mirror polished stainless steel substrates kept at room temperature and 500 °C. At the elevated temperatures, the desorption of adsorbates and condensate at the substrate surface are the most important factor which change the morphology of the splats, from irregular- splash morphology to disk-like shape. Splat morphology can determine deposit microstructure and improve the coating properties. The morphology of individual splats and the post treated films were studied using scanning electron microscopy. Results indicated that the porosity in the film produced at room temperature was higher than that in the film deposited on the heated substrates. Also, post heat treatment can improve coating properties

BaTiO 3 coatings are very promising for a wide range of applications in microelectronics because of their high dielectric constant and low leakage current. In this study, atmospheric plasma spraying is used to produce thick BaTiO 3 coatings and their microstructural features and dielectric properties are examined. The coatings were mainly composed of amorphous phase with small amounts of crystalline phase due to the incorporation of partially-molten droplets. The as-sprayed coatings were crystallized to BaTiO 3 by low temperature heat treatment and a mixture of BaTiO 3 and BaTi 2 O 5 at higher temperatures. At 1200 °C, the coating formed an equiaxed grain structure due to sintering effects and the dielectric constant was significantly improved.

A low-temperature, atmospheric-pressure spraying process was recently developed that facilitates the formation of highly functional films on any type of substrate using metal or nonmetal powders. This paper describes the new process and explains how different parameters, such as spraying distance, exit gas velocity, nozzle diameter, and particle size, affect the thickness, area, and composition of copper and barium titanate films on alumina, copper clad, and wafer substrates.

BaTiO3 has been successfully sprayed by HVOF to produce dense 25-150 µm thick deposits for use as dielectric and capacitive layers within prototype multilayer conformal electronics. Parameter optimization has been shown to play a critical role in the effective spraying of these materials as thin structurally homogeneous deposits. The affect of standoff distance and combustion chamber size on the phase structure of the coatings have been studied and related to the dielectric properties of the layer. The proportion of crystalline to amorphous phase was found to be critically dependent upon the degree of melting of the particles in the flame and the rate of cooling of the deposits. The crystalline/amorphous ratio is directly related to the dielectric properties of the layer with greater crystallinity giving higher values of dielectric constant. Microcracks and splat/splat interfaces are also believed to adversely affect the dielectric properties. The maximum dielectric constant (K) values achieved using the HVOF method for deposition have been in the range 70-115.