Study of APS and conventional sintering parameters for the manufacture of TiO2 targets for PAPVD

In surface science of functional oxides, titanium dioxide (TiO2) is one of the most investigated crystalline systems either in rutile or anatase phases. In this work commercial TiO2 powders are used to study the required process conditions to obtain TiO2 targets by Atmospheric Plasma Spray (APS) and conventional sintering, with suitable physical and chemical properties to be source material for Plasma Assisted Physical Vapor Deposition (PAPVD) for technological and medical applications. Two three factor Box Behnken experimental designs combined with surface modeling were employed to estimate the influence of spraying parameters (gun current, Ar/H2 ratio and standoff distance) and sintering parameters (heating rate, sintering temperature and holding time) within the targets microstructure (cracks and pores in cross section) and phases composition. The microstructure and composition of APS-deposited targets and sintered ones were characterized by Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD). The lowest defects percentages of the targets manufactured in this work were 0.41 ± 0.30 % for APS-deposited targets and 0.05 ± 0.04 % for the sintered ones using the optimal parameters suggested by the statistical model, which allowed confirming the advantages of sintering process and limitations of APS in terms of microstructural homogeneity, but also of the use of design of experiments in the modeling of systems of many variables when there is not diagnostic equipment of the processes available. © Published under licence by IOP Publishing Ltd