Effect of pre-annealing on NO32- centers in synthetic hydroxyapatite

• Published in: Radiation measurements Vol. 47; no. 10; pp. 970 - 973
• Main Authors: Nosenko, V.V., Vorona, I.P., Ishchenko, S.S., Baran, N.P., Zatovsky, I.V., Gorodilova, N.A., Povarchuk, V.Yu
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01-10-2012; Elsevier
• Subjects: Apatite; Earth sciences; Earth, ocean, space; EPR; Exact sciences and technology; Geochronology; Isotope geochemistry. Geochronology; NO32- centers; Apatite; NO32- centers; EPR; apatite; NO; electron paramagnetic resonance; phosphates; temperature; centers; nitrate ion; nitrates; annealing; carbonates; irradiation
• ISSN: 1350-4487; 1879-0925
• DOI: 10.1016/j.radmeas.2012.08.008

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.
► Effect of pre-annealing of γ- or UV- irradiated HAP on NO32- centers were analyzed. ► Pre-annealing of HAP with NO32- and CO32- does not change the parameters of NO32-. ► Pre-annealing of HAP with NO32- changes the hyperfine parameter A⊥ of NO32-. ► Two new NO32- centers in γ-irradiated HAP with NO32- were observed. ► Dependence of NO32- amount on the annealing temperature in HAP is non-monotonous.