Design of advanced one-step hydroxyapatite coatings for biomedical applications using the electrostatic spray deposition

[Display omitted] •Biomedical nanostructured CaP coatings designed by electrostatic spray deposition.•An organic phosphorus(V) precursor is used for the first time in the ESD process.•Low-cost electrospraying of single-phase HAP coated on Ti6Al4V in one step.•In-depth study of hydrolysis and evaporation of the P(V) precursor during ESD.•HAP composition and morphology preserved with an IR post-heat treatment. Calcium phosphate ceramics (CaP), particularly hydroxyapatite Ca10(PO4)6(OH)2 (HAP), are widely used as surface coatings on top of titanium and its alloys in biomedical applications thanks to their ability to form strong bonds with natural bone tissues. In this paper, the electrostatic spray deposition technique (ESD) by using an organic phosphorus (V) precursor is proposed as an alternative to the widely used plasma-spraying process. This bottom-up approach enables the one-step fabrication of single-phase crystalline HAP coatings with unique morphologies. The microstructure and composition of the deposited CaP layers result from a delicate compromise between the physicochemical properties of the precursor solution and the ESD deposition conditions. An in-depth study of their structural, microstructural, compositional properties and their reactivity with Ti6Al4V is undertaken. It shows that the Ca/P molar ratio and the nature of phases are strongly dependent on hydrolysis and evaporation of the P(V) precursor in the ESD process. Optimized deposition conditions are found by using solvents of low-boiling point, for which the coatings deposited above 325 °C correspond to a well crystalline, nanostructured, and single-phase HAP. Infrared heat treatment of a coating prepared from the one optimized precursor solution promotes nanostructured HAP.