Effect of pre-annealing on NO32- centers in synthetic hydroxyapatite |
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Authors: | VV Nosenko IP Vorona SS Ishchenko NP Baran IV Zatovsky NA Gorodilova VYu Povarchuk |
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Institution: | 1. Institute of Semiconductor Physics of NAS of Ukraine, 45 pr. Nauky, Kiev 03028, Ukraine;2. Taras Schevchenko National University, 64 st. Volodymyrska, Kiev 01033, Ukraine;3. Institute of Physics of NAS of Ukraine, 46 pr. Nauky, Kiev 03028, Ukraine |
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Abstract: | Effect of pre-annealing of synthetic hydroxyapatite (HAP) on properties of γ- and UV- induced NO32- centers was studied by electron paramagnetic resonance (EPR). Nitrate-containing hydroxyapatite powders ((N)HAP)) and the powders with an admixture of carbonate and nitrate ions ((C,N)HAP) were annealed in the temperature range Tann = 20 °C ? 600 °C before irradiation. It was found that pre-annealing of (N)HAP samples changes the parameters of NO32- centers while no changes took place in (C,N)HAP. Moreover, at the pre-annealing temperatures Tann > 200 °C two new NO32- centers were observed in (N)HAP samples; they are characterized by larger value of A⊥ (3.67 and 4.41 mT) as compared to the known centers. It was also found that the dependence of NO32- centers amount on Tann is non-monotonous in both types of samples. Presumably this is caused by the escape of water molecules from HAP during the annealing and essential modification of the defect subsystem of HAP. |
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