Mechanochemical processing of BaZr1-yYyO3_delta (y=0.15, 0.20) protonic ceramic electrolytes: Phase purity, microstructure, electrical properties and comparison with other preparation routes

authors	Antunes, I; Perez-Coll, D; Nasani, N; Soares, HS; Mather, GC; Frade, JR; Fagg, DP
nationality	International
journal	INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
author keywords	Perovskite; Yttrium-doped barium zirconate; Defect chemistry; Modelling; Transport properties; Proton ceramic fuel cells
abstract	BaZrO3-based materials have been intensively researched due to their potential application as high-temperature proton conductors in devices such as proton ceramic fuel cells (PCFCs), separation membranes and electrolysers. Nonetheless, their implementation in these devices has often been constrained due to their processing difficulties, namely the formation of Ba-deficient compositions, coexistence of separate perovskite phases or the formation of segregated phases of the acceptor dopant. In this context, the current article shows mechanosynthesis to be an efficient preparation method for Ba(Zr,Y)O3-delta materials, producing pure powders, containing nanometric crystallites, that offer good densification and grain growth. The phase formation, microstructure and electrical properties of the most promising BaZr1-yYyO3-delta compositions, with yttrium contents of y = 0.15 (BZY15) and y = 0.20 (BZY20) are investigated and compared with literature data of materials made by other processing routes. Such a comparison highlights that phase separation of such compositions, commonly reported in the literature, does not occur for these mechano-synthesised materials of high homogeneity. Furthermore, high electrical performances can be obtained by this technique that can compete with some of the best reported in the literature. Electrical conductivity as a function of both oxygen and water partial pressure, in the temperature range of 550 degrees C 850 degrees C, are measured for both compositions and the partial conductivities of protons, oxygen vacancies and electron holes are determined from the defect model. The electron-hole conductivity of BZY20 is observed to be higher than that of BZY15 under all conditions, while proton and oxide-ion conductivities are shown to be higher for the composition BZY15. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
publisher	PERGAMON-ELSEVIER SCIENCE LTD
issn	0360-3199
isbn	1879-3487
year published	2021
volume	46
issue	25
beginning page	13606
ending page	13621
digital object identifier (doi)	10.1016/j.ijhydene.2020.06.222
web of science category	16
subject category	Chemistry, Physical; Electrochemistry; Energy & Fuels
unique article identifier	WOS:000634962100009