The properties of synthetically hydroxyapatites are significantly affected by chemical or radiological exposures making these materials good sensors. Since early sixties hydroxyapatites single crystals have been investigated for sensors and laser host applications. Hydroxyapatites are naturally occurring mineral calcium apatite with the formula Ca5(PO4)6(OH)2 . When the OH− ion is replaced by halides (F, Cl) and carbonate these are referred as haloapatites such as fluorapatite and chlorapatite. These materials generally belong to hexagonal symmetry. Most of the times naturally occurring apatite contain impurities and instead of transparent white these appear to be brown, green or yellow. Recently it has been realized that major portion of the body bone is some form of hydroxyapatite. We have studied several compositions of hydroxyapatites and synthesized by using nanoparticles of parent components and developed growth by sintering and grain growth. We observed that during grain growth hexagonal morphology is formed which changes to glassy phase depending on the cooling conditions and compositions.
SignificanceThe glassy and crystalline hydroxyapatites that affect the metabolic processes such as tissue growth and healing are affected by the electrical, electrochemical, and optical properties investigated in this study.AimThe aim of the present study is to determine effects of high-energy radiation and impurities on the electrical and optical properties of hydroxyapatites responsible for tissue growth and tendency of glass forming ability.ApproachThe approach of the study involves synthesis using carbonates, oxides, silicates, phosphates, and borates of parent materials using elevated temperature and low-temperature flux process. High-energy radiation effects were studied by exposing hydroxyapatites with 5 μCi Cs137 γ- ray source. Morphology was studied to determine dissolution and glass formation of additives such as titanium, gallium, and selenium.ResultsIrradiation of silicate bio glasses showed huge effects on the electrical characteristics, such as dielectric constant (hence polarity) and resistivity of the materials while optical properties showed insignificant changes. Morphological studies showed transition of faceted to nonfaceted structure.ConclusionExposure for the bias voltage of 50 to 1000 mV in the range of 100 to 100000 Hz frequency range showed a large decrease in the dielectric constant and increase in resistivity. The IR and Raman spectra for irradiated glasses exposed for 24 h showed a small change. Morphological results showed that substitution of gallium, magnesium, and /or titanium affects the transition to the glass formation. The addition of selenium showed enormous potential to improve the mixing and glass formation without titanium and gallium precipitates in the matrix.
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