Nano calcium phosphates doped with titanium and fluoride ions: sinterability and stability of phases

Güngör Geridönmez, Serap
The purpose of this study was to synthesize calcium phosphates doped with titanium and fluoride ions in different combinations. Pure and doped calcium phosphates were synthesized by a precipitation method. The synthesized materials were sintered at 1100ºC and 1300ºC for 1h. The ceramics were characterized by density measurements to determine the effect of sintering temperature. Presence of phases and bonds were characterized by XRD diffraction and FTIR spectroscopy. Grain sizes of the samples were obtained by SEM. Microhardness test was applied on the samples to determine the mechanical properties of the samples. It was observed that Ti4+ addition decreased the density of samples significantly at 1100°C, whereas increasing the sintering temperature to 1300°C caused an increase. Increasing the F- ion amount increased the densification at 1100°C when molar ratios were 1.0, 1.25, 1.50 and decreased the density at 1300°C when Ca /P molar ratios were 1.0, 1.25, 1.67 and 2.0. Ti4+ and F- co-doped samples showed variety in their density behaviour after the sintering at 1100ºC and 1300ºC. The XRD analyses demonstrated that for Ca to P ratio 1 at 1100°C, β-CPP phase, when sintering temperature was raised to 1300°C, as a second phase of β-CPP and α-TCP observed. Increasing the molar ratio to 1.25 and 1.50 demonstrated β-TCP and/or β-CPP and β-TCP/ HA at 1100°C and β-TCP and/or β-CPP, α-TCP, TiO2 and HA, α-TCP, TiO2 phases at 1300°C, respectively. In higher Ca/P molar ratios of 1.67 and 2.0, HA, β-TCP, α-TCP, CaO, TiO2, CaTiO3 and HA, CaO, α-TCP, CaTiO3 phases were determined. Increasing the sintering temperature to 1300°C resulted in transformation to α-TCP. In FTIR spectroscopy analysis, when the samples with molar ratio of 1, 1.25, 1.50, 1.67 and 2.0, sintered at 1100°C, the characteristic bands of β-CPP, OCP/β-TCP, β-TCP/HA, HA and HA were observed, respectively. With increasing the sintering temperature to 1300°C, samples with molar ratio of 1.0 and 1.25 revealed additional secondary characteristic peaks of HA and β-TCP. SEM images revealed that sintering temperature and ion amounts of dopants had significant effect on grain sizes of the samples. The grain sizes were generally increased when sintering temperature rose from 1100°C to 1300°C. The μ-hardness test demonstrated that Ti4+ and F- ions in large amounts had positive effect on the mechanical properties at the sintering temperatures of 1100°C and 1300°C.


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Citation Formats
S. Güngör Geridönmez, “Nano calcium phosphates doped with titanium and fluoride ions: sinterability and stability of phases,” Ph.D. - Doctoral Program, Middle East Technical University, 2012.