Combinatorial development of LSC-113/LSC-214 cathode materials for intermediate temperature solid oxide fuel cells

Tezin Türü: Yüksek Lisans

Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Mühendislik Fakültesi, Metalurji ve Malzeme Mühendisliği Bölümü, Türkiye

Tezin Onay Tarihi: 2017

Öğrenci: DOĞANCAN SARI

Eş Danışman: YUNUS EREN KALAY, TAYFUR ÖZTÜRK

Özet:

Solid oxide fuel cells are environmentally friendly, efficient and fuel versatile energy conversion devices which suffer from high operating temperatures. For lowering the operating temperatures of solid oxide fuel cells (SOFC), LSC-113/LSC-214 composite cathodes have recently attracted much attention due to their enhanced kinetics. However, the full potential of this novel system is still unknown. In this study, a combinatorial approach was used to develop cathode materials which would reduce operating temperatures of SOFCs to the range 500 - 600 ⁰C. The kinetics of cathodic processes were investigated for LSC-113/LSC-214 composite cathode films deposited with magnetron sputtering and screened with measurement of EIS responses on symmetric cells. The study is made up of three parts. Part I is related to the fabrication of sputtering targets. Part II comprises the main study which was on combinatorial screening of LSC-113/LSC-214 co-sputtered cathodes, and Part III is related to the stability of composite LSC cathodes for prolonged use; In the first part of this study, a novel approach is illustrated to fabricate sputtering targets for thin film production. In this approach, deformable dies made up of poly-tetrafluoroethylene (Teflon) were used instead of conventional rigid dies. It was shown that this method is suitable for products of low volume productions. With the use of teflon rings LSC-113 and LSC-214 sputtering targets were succefully fabricated and used for the deposition of thin film cathodes. In the second part, a combinatorial approach was used to obtain the optimum composition in LSC-113/LSC-214 composite system. A thin film composite cathode library was obtained by co-sputtering of LSC-113 and LSC-214 onto suitably positioned substrates each with controlled compositions. The cathode library was screened with an electrochemical impedance spectroscopy and showed that co-sputtered LSC-113/LSC-214 composite cathodes have low area specific resistance values (ASR) as compared to those reported in the literature. Practically useful ASR value of 0.15 Ω.cm2 was obtainable at many of the compositions in LSC-113/LSC-214 below 700 ⁰C. The best compositional range is 0.40