STRUCTURAL AND LUMINESCENT PROPERTIES OF EUROPIUM-DOPED AND UNDOPED HYDROXYAPATITE POWDERS SINTERED BY SPARK PLASMA

This paper studies the structural and photoluminescent properties of hydroxyapatite (HA) and europium-doped hydroxyapatite (HA:Eu) synthesised by the hydrothermal method and sintered by the spark plasma sintering (SPS) technique. HA and HA:Eu powders, synthesised at pH of 10, 11 and 12, were characterised by means of infrared spectroscopy, X-ray diffraction, scanning electron microscopy, Raman spectroscopy and luminescence spectroscopy. The HA and HA:Eu samples were sintered using the SPS technique at 900 and 1200 °C. It was determined that the HA and HA:Eu powders crystallised in the hexagonal phase, which is stable until 900 °C. The presence of Eu3+ ions tended to stabilise the hexagonal phase of hydroxyapatite at 1200 °C. Undoped hydroxyapatite sintered at 1200 °C revealed a significant amount of tricalcium phosphate (β-TCP) as a result of its decomposition. By increasing the heat treatment temperature, different emission lines (⁵D₀→ ⁷F₀, ⁵D₀→ ⁷F₁ and ⁵D₀→ ⁷F₂ transitions) were obtained due to calcium site substitution by the europium ions in the HA structure.