Structure-Dielectric Behavior Relationships in HVOF Sprayed BuTiO ₃

BaTiO₃ has been successfully sprayed by HVOF to produce dense 25-150μm 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 effect 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 effect the dielectric properties. The maximum dielectric constant (K) values achieved using the HVOF method for deposition have been in the range 70-115.