The stoichiometric hydroxyapatite, Ca 10 (PO 4 ) 6 (OH) 2 is prepared by an aqueous precipitation method at room temperature, the main reactants were Ca(OH) 2 and H 3 PO 4 without addition of ammonia solution. The sample was analyzed by Fourier transformed infrared spectroscopy (FTIR) which reveals the presence of a small amount of carbonate due to absorbance of carbon dioxide from the air during synthesis process. The crystal structure was carried out by X-ray powder diffraction data and the Rietveld method using FullPROF software. We confirmed that this material has a hexagonal structure (space group P63/m; Z = 1). Unit-cell parameters with higher precision (a = b = 9.4159(4) Å , c = 6.8819(3) Å, α = β = 90°; and γ = 120°).
Vanadium dioxide (VO2) have attracted tremendous interest in recent years due to their semiconductor-metal transition near room temperature. In this work, we report numerical simulation of the optical properties of VO2 thin layers which include the index of refraction, the coefficient of extinction, the reflectance and the transmittance. In this sense, we used the Model of Drude-Lorentz for calculating coefficients at from the optical parameters n and k using the determination of the dielectric constant ε (ω, T). Knowing that the semiconductor-metal transition temperature of VO2 is 68 °C, the thickness effect on the optical properties of VO2 thin films has been studied by transmittance simulations. Our results revealed a significant changes in optical properties of VO2 thin layers, which produces many interesting applications especially for smart windows.
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