Solid solution formation at the sintering of hydroxyapatite–fluorapatite ceramics

Abstract

Fluorhydroxyapatite ceramics are increasingly studied for the use as biomaterials due to their good integration ability in the bone tissue and higher resorption resistance compared to the common hydroxyapatite (HA) ceramics. This study is aimed at the X-ray diffraction investigation of the interaction between HA and fluorapatite (FA) particulates in the sintering temperature range up to 1300 8C. The lattice parameters were calculated in dependence of both the FA content in the powder mixtures and the sintering temperature. From those data, the solid solution formation is concluded, at least in the temperature range from 1200 to 1300 8C. Energy-dispersive X-ray microanalysis confirmed the fluorine distribution to be almost uniform in the sintered at 1300 8C ceramics. q

Calcium orthophosphates

“…If the F/OH ratio is either uncertain or not important, the chemical formula of FHA and HFA is often written as Ca 10 (PO 4 ) 6 (F,OH) 2 . The lattice parameters, crystal structure, solubility and other properties of FHA and HFA lay in between those for the chemically pure FA and HA 431 - 435 …”

F-substituted hydroxyapatite nanopowders: Thermal stability, sintering behaviour and mechanical properties

“…In agreement with the literature [27,31], a slight decrement of lattice constants was detected. The value of the calculated a-axis of F-half substituted HAp was between that of HAp and that of fluoroapatite (Ca 10 (PO 4 ) 6 F 2 ) according to JCPDS #15-0876 (a = 9.364 Å ) [25,31], due to the smaller size of F À (1.32 Å ) with respect to OH À (1.68 Å ) [1,11,27,32]. On the other side, the lattice parameter c does not significantly change [25].…”

Mechanochemical and Low‐Temperature Synthesis of Nanocrystalline Fluorohydroxyapatite/Fluorapatite

“…Hence, at lower degrees of fluoridation the apparent solubility of FHA/FA declines significantly. Also, FHA/FA has a better thermal and chemical stability than HA . This phenomenon was successfully described by Elliott et al .…”

“…Besides, HA and FHA/FA, which are the main inorganic constituents of bones and teeth, have been attracting great attention for numerous biomedical applications, such as drug delivery carriers, catalyst carriers, and adsorbents . The performances of HA or FHA/FA in these applications are strongly dependent on their nanoscale morphology and crystallinity …”