Fabrication and Characterization of Thin Film SrCo0.8Nb0.1Ta0.1O3-Δ By Pulsed Laser Deposition

Abstract

High working temperature(≥800 °C) of solid oxide fuel cell(SOFC) causes high cost of balance of plant, long start up time, and low durability. To overcome these barriers, lowering the working temperature of SOFC is one of the most attractive ways and such strategy has been researched through the fabrication of thin electrolyte and developing new perovskite cathode material. Recently, mixed ionic electronic conducting(MIEC) cathode material, SrCo0.8Nb0.1Ta0.1O3-δ (SCNT), has been developed by Li et al. and the SOFC with the cathode showed high performance(1.22W/cm2) at low working temperature (500 °C) with 14µm thick gadolinia doped ceria(GDC) electrolyte[1]. To apply SCNT to SOFC with thin electrolyte(≤1µm), the cathode must be fabricated on the electrolyte without high temperature sintering process(≥1000 °C) because of the weak mechanical strength of thin electrolyte. In this work, pulsed laser deposition(PLD) method was employed for the fabrication of thin film SCNT. PLD has been used widely for perovskite material deposition because of its high preservability of stoichiometric ratio of its original target material. However, the deposition temperature of PLD has a great influence on both physical and chemical structure of the film which means oxygen reaction activity(ORR) of the film also varies as temperature changes. Therefore, thin film SCNT was deposited by PLD at various temperature condition in this work to see the diversity of thin film characteristic for understanding the feasibility of application of SCNT to thin film SOFC (TF-SOFC). Powder and PLD target of SCNT were both prepared by the method Li et al. used, solid state reactive sintering(SSRS). The film was firstly deposited on Si wafer at various temperature (room temp, 500, 600, 700 °C) by PLD. Field emission scanning electron microscope (FE-SEM) and focused ion beam-SEM (FIB-SEM) were used to see the nano-structure of the film and deposition rate. 75mTorr of oxygen atmosphere was enough to make the structure of thin film deposited at room temperature very porous but dense film was observed at the temperature higher than 500 °C. The atomic ratio and crystallinity of each film were identified by X-ray spectroscopy(XPS) and X-ray diffraction(XRD) respectively. Through the understanding the physical and chemical variation of PLD deposited SCNT at different temperature condition, the best PLD deposition condition of SCNT for TF-SOFC was derived. Acknowledgment This work was supported by the Global Frontier R&D Program on Center for Multiscale Energy System funded by the National Research Foundation under the Ministry of Science, ICT & Future Planning, Korea (2012M3A6A7054855) References [1] M. Li et al., “A niobium and tantalum co-doped perovskite cathode for solid oxide fuel cells operating below 500 °c,” Nat. Commun., vol. 8, no. 5, pp. 1–9, 2017.