Investigating Phase and Electrical Properties of Calcium-Doped Yttrium Iron Garnet

Abstract

Literature studies have shown that Ca0.5Y2.5Fe5O12-δ can be a promising cathode material for intermediate temperature solid oxide fuel cell (IT-SOFC) 1. As it exhibits higher electrical and ionic conductivity compared to several other kinds of rare-earth garnets 2. However, given the high resistivity (> 1012 Ω cm at room temperature) and less-explored oxide ion conductivity of its parent phase yttrium iron garnet (Y3Fe5O12, YIG), the effect of calcium doping on the electronic and ionic properties has not been fully studied yet 3. In this work, polycrystalline samples of Ca-doped YIG, with general chemical formula CaxY3-xFe5O12-δ (x=0, 0.1, 0.3, 0.5 and 0.7), were prepared and phase characterized by powder X-ray diffractometer. The oxygen non-stoichiometry was determined by iodometric titration at room temperature and thermogravimetric analysis (TG) at elevated temperatures. Total electrical conductivity was measured by four-probe DC method, and ionic conductivity was calculated by using a modified Hebb-Wagner polarization method. As a result, the ionic transference number was calculated and discussed in relation to its potential applications. Reference: Zhong, W., Ling, Y., Rao, Y., Peng, R. & Lu, Y. Calcium doped Y3Fe5O12 as a new cathode material for intermediate temperature solid oxide fuel cells. J. Power Sources 213, 140–144 (2012).Kharton, V. V. et al. Ionic Transport in Gd3Fe5O12- and Y3Fe5O12-Based Garnets. J. Electrochem. Soc. 150, J33 (2003).Lehmann-Szweykowska, A., Wojciechowski, R. J., Gehring, G. A. & Tobijaszewski, I. Quasiparticles in Calcium Doped Yttrium-Iron Garnets. Acta Phys. Pol. A 91, 423–426 (1997).