Physicochemical properties of calcium phosphate coatings produced by pulsed laser deposition at different water vapour pressures.

Calcium phosphate coatings were produced by pulsed laser deposition from targets of non-stoichiometric hydroxyapatite (Ca/P = 1.70) at a substrate temperature of 485 degrees C and different processing pressures of water vapour: 0.15, 0.30, 0.45, 0.60 and 0.80 mbar. The physicochemical properties of these coatings were studied using Fourier-transform IR spectroscopy (FT-IR) and energy dispersive X-ray analysis (EDX). A minimum pressure of water vapour was necessary in order to obtain a crystalline coating, as deduced from the FT-IR spectroscopy of these coatings. This analysis also revealed that when the deposition pressure of water vapour was further increased, the coatings were less crystalline and the content of hydroxyl groups, the carbonate substitution for phosphate, and the Ca/P ratio, as measured by EDX, were lower. These effects can be explained by a combined substitution of carbonate and HPO4(2-) for phosphate, being predominant the carbonate substitution at low pressures and the HPO4(2-) substitution at high pressures.

Hydroxyapatite coatings: a comparative study between plasma-spray and pulsed laser deposition techniques.

A comparative study between hydroxyapatite coatings produced by two different techniques, plasma spray (PS) and pulsed-laser deposition (PLD) was carried out. Plasma spray is currently commercially used for coating dental and orthopaedical implant devices, and pulsed-laser deposition (or laser-ablation deposition) gave good results in the field of high critical temperature superconductive thin films, and is being applied to produce calcium phosphate coatings for biomedical purposes. X-ray diffraction was used to control the crystallinity of the coatings, scanning electron microscopy for the surface and cross-sectional morphology, and the pull test to determine the tensile strength of the coatings. This study reveals that the pulsed-laser deposition technique appears to be a very good candidate to replace the plasma spray in many biomedical applications, because it overcomes most of the drawbacks of the plasma spray.

Structural analysis of calcium phosphate coatings produced by pulsed laser deposition at different water-vapour pressures.

Calcium phosphate coatings have been produced by pulsed laser deposition (PLD) at different water-vapour pressures. Rietveld refinement of X-ray diffraction (XRD) data allows us to determine that the structure of these coatings is apatitic with carbonate substitution for phosphate. The carbonate substitution decreases when the chamber pressure is raised, a fact that has been corroborated by Fourier transform-infrared (FT-IR) spectroscopy. Carbonate concentrations between 5 and 17 wt% have been calculated for the crystalline samples. Amorphous coatings are produced at the lowest and highest pressures due to the high carbonate concentration in the first case, and possibly to another type of substitution (Mg(2+), HPO(2-)4, P2O(4-)7) or the inherent kinetics of the PLD process, in the second case.