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Synthesis And Conducting Properties Of Silicate Oxyapatites

Posted on:2007-12-19Degree:DoctorType:Dissertation
Country:ChinaCandidate:G L WangFull Text:PDF
GTID:1101360185966753Subject:Materials science
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The synthesis method,structure and conduction mechanism of oxyapatite type oxygen ion conducting materials were studied in the thesis.The relation of the composition,structure and conduction of oxyapatites were investigated.11 types of the silicate oxyapatites were synthesized successfully via a sol-gel method.These oxyapatites include:the stoichiometric A2La8(SiO4)6O2 (A=Ca,Sr, Ba),the oxygen-deficient Ca2+xLa8-x(SiO4)6O2-0.5x,the cation vacancies Ca2-3x La8+2x(SiO4)6O2 and Ca3-3xLa7+2x(SiO4)6 O1.5,the oxygen-excess CaxLa10-x(SiO4)6 O(3-x)/2, La10-x(SiO4)6O3-1.5x,CaxLa9.67-2x/3 (SiO4)6O2.5 and ALa9(SiO4)6O2.5 (A=Ca,Sr, Ba),the Si-doped La9(SiO4)6-x (VO4)xO1.5+0.5x, La10(SiO)4)6-x (AlO4)xO3-0.5x and La10(SiO4)6-x(GaO4)xO3-0.5x. Comparing with the solid state synthesis, the sol-gel synthesis has the advantages of low temperatures and short time.In addition,the resulting products have high conductivities.The obtained compounds were characterized by X-ray diffraction (XRD), infra-red spectrum(IR), Raman spectrum(R), thermal analysis (TGA-DTA) and scanning electron microscopy(SEM) respectively. The results indicate that they all have the apatite phase. The obtained silicate oxyapatites crystallize in the hexagonal system. The space group of all samples are P63/m,except the Si-doped materials,which are P63. The bigger the ionic radiu,and the more the oxygen ion, the larger the volume of unit cell.The vbrational Mode of Ca2La8(SiO4)6O2 were determined by the group theory and correlation methods,they are 12Ag+9Au+9Bg +12Bu+SE1g +13E1u+13E2g+8.E2u.Irifra-red active modes are 8Au+l2E1u,and Raman active modes are 12Ag+8E1g+13E2g.Electrochemical impedance spectroscopy (EIS) measurements show that EIS of all samples could be Kramers-Kronig test,and complex impedance diagrams of silicate oxyapatites measured at various temperatures could present bulk,grain boundary and electrode three species. Temperature dependence of conductivity for the silicate oxyapatites basically follows Arrhenius equation in a wide range,but a slight deviation was observed at higher temperature.The conduction...
Keywords/Search Tags:Silicate oxyapatite, Synthesis, Oxygen ion conductor, Interstitial oxygen conduction, Electrochemical impedance spectroscopy(EIS)
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