., Fitriana (2022) Investigasi Struktur, Sifat Listrik Dan Magnet Dari Perovskit Ba0.5Sr0.5FeO3-δ Didoping La, Cu, Dan Zr Sebagai Katoda SOFC. Doctoral thesis, Institut Teknologi Sepuluh Nopember.
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Abstract
Oksida perovskit (ABO3) berbasis Ba0.5Sr0.5FeO3-δ (BSF) telah berhasil disintesis dan dikarakterisasi pada penelitian ini. BSF didoping Cu2+ pada situs B menjadi Ba0.5Sr0.5Fe1-xCuxO3-δ (BSFC-x, x = 0-0,2), BSF didoping Cu2+ dan Zr4+ pada situs B menjadi Ba0.5Sr0.5Fe0.85Cu0.1Zr0.05O3-δ (BSFCZ), dan BSF didoping La3+ pada situs A serta doping Cu2+ pada situs B menjadi double perovskit LaBa0.5Sr0.5Fe1.8Cu0.2O6-δ (LBSFC). Semua material disintesis menggunakan metode sol-gel self-combustion. Sampel dikarakterisasi difraksi sinar-x (XRD), x-ray absorption spectroscopy (XAS) yang terdiri dari x-ray absorption near-edge spectroscopy (XANES) dan extended x-ray absorption fine structure (EXAFS), analisis termal (TGA), konduktivitas listrik, karakterisasi kemagnetan (SQuID), titrasi iodometri, dan Scanning Electron Microscope (SEM). Pada sampel BSFC-x memiliki struktur kubik pada x = 0-0,1, dan tetragonal pada x =0,15 – 0,20. Sedangkan pada BSFCZ dan double perovskite LBSFC memiliki struktur kubik dan ortorombik. Perubahan oxidation state pada situs B diamati dengan XANES, menunjukkan campuran antara Cu2+ dan Cu3+ akibat adanya oksigen pada situs oktahedron ABO3, sementara oxidation state Fe adalah campuran antara Fe3+ dan Fe4+. Konduktivitas tertinggi diperoleh dari BSFC-0.1 yaitu 60 S/cm dan LBSFC dengan 150 S/cm. Peningkatan konduktivitas elektronik pada BSFC-x, BSFCZ, dan LBSFC disebabkan oleh simetri unit sel yang tinggi, serta pembentukan dan migrasi vakansi oksigen dalam kisi akibat adanya ketidakseimbangan muatan pada situs B karena doping Cu2+ yang memiliki valensi lebih rendah daripada Fe3+ dan Zr4+. LBSFC mengalami peningkatan konduktivitas menjadi tiga kali BSFC-0,1 dikarenakan adanya doping La3+ pada situs A yang mengakibatkan ketidakseimbangan muatan dan menghasilkan kompensasi ionik yaitu pembentukan vakansi oksigen. Adanya doping Cu dapat mengubah sifat magnet kuat menjadi magnet lemah akibat hilangnya interaksi antara orbital d dan p pada ikatan B-O-B.
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Perovskite oxide (ABO3) based on Ba0.5Sr0.5FeO3-δ (BSF) has been succesfully synthesized and characterized in this study. BSF doped with Cu2+at B-sie became Ba0.5Sr0.5Fe1-xCuxO3-δ (BSFC-x, x = 0-0.2), BSF doped with Cu2+ and Zr4+at B-site became Ba0.5Sr0.5Fe0.85Cu0.1Zr0.05O3-δ (BSFCZ), and BSF doped La3+ at A-site and Cu2+ and Zr4+ at B-site became a double perovskite LaBa0.5Sr0.5Fe1.8Cu0.2O6-δ (LBSFC). All materials were synthesized using the sol-gel self-combustion method. The sintered samples were characterized by x-ray diffraction (XRD), x-ray absorption spectroscopy (XAS) consisting of x-ray absorption near-edge spectroscopy (XANES) and extended x-ray absorption fine structure (EXAFS), analysis thermal conductivity (TGA), electrical conductivity, magnetic characterization (SQuID), iodometric titration, and Scanning Electron Microscope (SEM). BSFC-x has a cubic structure at x = 0-0.1, and tetragonal at x = 0.15 – 0.20. BSFCZ and double perovskite LBSFC have cubic and orthorhombic structures respectively. Changes in the oxidation state at site B were observed with XANES, showing a mixture of Cu2+ and Cu3+ due to the presence of oxygen vacancy at the ABO3 octahedral site, while the oxidation state of Fe is a mixture of Fe3+ and Fe4+. The highest conductivity was obtained from BSFC-0.1 which is 60 S/cm and LBSFC with 150 S/cm. The increase in electronic conductivity in BSFC-x, BSFCZ, and LBSFC is due to the high symmetry of the unit cell, as well as the formation and migration of oxygen vacancies in the lattice. Cu2+which has lower valence than Fe3+ and Zr4+ causes a charge imbalance at B-site which is compensated by the formation of an oxygen vacancy. LBSFC increased its conductivity to three times BSFC-0.1 due to the La3+ doping at A-site which resulted in a charge imbalance and resulted in ionic compensation, namely the formation of oxygen vacancies. The presence of Cu doping can change the properties of strong magnets into weak magnets due to the loss of interaction between d and p orbitals in the B-O-B bond.
| Item Type: | Thesis (Doctoral) |
|---|---|
| Uncontrolled Keywords: | konduktivitas elektronik, magnetik, oksida perovskit, oxidation state, struktur kristal, : electronic conductivity, magnetic, perovskite oxide, oxidation state, crystal structure |
| Subjects: | Q Science > QC Physics > QC100 Crystals. Q Science > QC Physics > QC271 Temperature measurements Q Science > QC Physics > QC451 Spectroscopy Q Science > QC Physics > QC610.3 Electric conductivity Q Science > QC Physics > QC765 Magnetic materials |
| Divisions: | Faculty of Science and Data Analytics (SCIENTICS) > Physics > 45001-(S3) PhD Thesis |
| Depositing User: | Fitriana Fitriana |
| Date Deposited: | 25 Feb 2022 00:51 |
| Last Modified: | 25 Feb 2022 00:51 |
| URI: | http://repository.its.ac.id/id/eprint/94683 |
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