High crystalline hydroxyapatite coating by eclipse type pulsed-laser deposition for low annealing temperature

Abstract

The eclipse type pulsed-laser deposition (PLD) scheme as a droplet-eliminated method with irradiation on a β-tricalcium phosphate (β-TCP) slab target was employed to achieve high density without holes, high purity, and high crystallinity hydroxyapatite (HAp) coating on a zirconia substrate with a low annealing temperature under an H2O vapor pressure. An obstacle ball was set between the target and the substrate so that ablated droplets would collide with the ball and be eliminated, while other ablated atoms went around the ball and were deposited on the substrate. A flat, transparent, and high-density coating layer was deposited on the substrate in an H2O vapor atmosphere at 0.1 Torr for different substrate surface temperatures from 20 °C to 650 °C. The phase of the coating layers was significantly changed from amorphous calcium phosphate to crystalline HAp when the temperature was set to over 360 °C, as determined from Raman microscopy measurements. Raman spectroscopy also showed that the HAp crystal size became larger as the temperature was increased to over 360 °C. It was concluded that the eclipse type PLD method with irradiation on a β-TCP target would improve the quality of HAp coatings and allow effective lowering of the annealing temperature.