Functionality of Lanthanum, Neodymium, and Praseodymium Nickelates as Promising Electrode Systems for Proton-Conducting Electrolytes

Abstract

Results obtained in synthesis and certification of new materials based on Ba-doped Ln₂NiO_4+δ as possible electrode candidates for electrochemical devices with solid-oxide proton-conducting electrolytes are presented. Single-phase materials of composition Ln_1.95Ba_0.05NiO_4+δ (Ln = La, Nd, and Pr) were obtained by using the citrate-nitrate synthesis method, and their thermomechanical, electrical, and electrochemical functionality was examined with the use of the dilatometric method, four-probe dc measurements, and electrochemical impedance spectroscopy, respectively. An integrated analysis of the data obtained shows that the highest electrical transport properties, which compare well with modern results, were reached for the Pr-containing nickelite. At the same time, this nickelite has an increased thermal expansion coefficient, which exceeds by ~20% that for the electrolyte material. These characteristics can be optimized by creating composite materials based on Pr_1.95Ba_0.05NiO_4+δ with a small fraction of the electrolyte component.