APATITE BASED OXIDES AS ELECTROLYTE FOR SOLID OXIDE FUEL CELL

• Main Author: ROSTIKA NOVIYANTI (NIM : 30507006);Ketua tim Pembimbing : Prof. Dr. Ismunandar; Anggota tim pe, ATIEK
• Format: Dissertations
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/15079
• Institution: Institut Teknologi Bandung

In an effort to develop Solid Oxide Fuel Cell (SOFC), here we studied the synthesis of lanthanum silicate apatite (La9,33+x(SiO4)6O2+3x/2) at low temperatures. In this research, we have synthesized lanthanum silicate apatite <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> (La9.33+x (SiO4)6O2+3x/2) from La2O3 and Na2SiO3 disolved in 3 M NaOH solution using hydrothermal method at of 240 oC for 3 days. <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> In an effort to improve the conductivity of the apatite we conducted studies and synthesis of doped apatite and codoped apatite using the same method. The starting materials of doped and codoped apatite are La2O3, Na2SiO3 and BaCO3, CaCO3, SrCO3 as dopant source (La site), and Ga2O3, MgO, GeO2 (Si site dopant). <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> Structure of the undoped, doped and codoped apatites were characterized. Characterization of apatite structure, doped and codoped apatite was carried out using X-ray diffraction, infrared spectra and solid 29Si-NMR. The morphology of the resulting solids was also presented. In order to correlate the conduction properties of the solid apatite, conductivity measurements were taken. <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> X-ray diffraction characterization shows that the apatite and doped apatite crystallizes in hexagonal lattices with P 63/m space group. Formation of apatite and doped and codoped apatite were confirmed by change in lattice paremeters and cell volume as a function of the dopant type and size. Thus, it could be concluded that the lattice parameter and cell volume were affected by the dopant type and size. The impedance measurement showed that the La9, 33Si6O26 apatite has ionic conductivity of 2.95 × 10-4 S cm-1 at 500 oC. It was found that La9.BaSi6O26.5 has the highest ionic conductivity (s500 = 2.53 × 10-4 S cm-1) <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> among the apatites doped at La sites, while the La9.8Si5GeO26.7 with s500 = 3.83 × 10-4 S cm-1 is the most conductive among the apatites doped at Si sites, and <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> La8.8BaSi5GeO26.2 (s500 = 3.79 × 10-4 S cm-1) is the most conductive among the apatites doped at both La and Si sites. <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> The chemical shift at about -80 ppm in the 29Si NMR spectra of the apatites were assigned as distorted SiO4 groups, the intensity of which is proportional to the conductivity of the apatites. Apatites with high conductivity were those that have high intensity peaks at -80 ppm.