Optical and Morphological Study of Hydroxyapatite on Titanium Dioxide Particles for Photovoltaic Applications

In this study, a natural mineral termed hydroxyapatite (HA) (Ca10(PO4)6(OH)2) was produced with TiO2 stoichiometrically by normal sol-gel process. An investigation on how the different percentage weights of HA on TiO2 can affect its optical and morphological properties was carried out, while the morphological nature and elemental composition were verified through scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDX) analysis. Consequently UV–visible spectroscopy was used to measure the absorbance data, where optical constants such as absorption coefficient, extension coefficient, refractive index, transmittance, absorbance, thermal conductivity, the electron-phonon interaction and steepness parameter were evaluated. According to the optical examination, the transmittance in the visible range is between (400 and 800 nm), and the absorption response in the UV region is between (200 and 400 nm) with an absorption edge occurring between (650 and 950 nm). The value of the absorption coefficient (α) and extension coefficient (k) of HA/TiO2 increased with an increase in the percentage weight (wt%) of HA. Equally, the optical conductivity increases with an increase in photon energy. In addition, the band gap energy decreases as the percentage weight of HA increases.