Investigation of effect of Al3+-Doping on mass/charge transport properties of La2NiO4+δ by blocking cell method

Abstract

In this work, effect of doping of a fixed-valence non-transition metal ion Al3+ on B-site of La2NiO4+δ (LNO) system is investigated by a blocking cell experiment. The mass and charge transport properties of La2Ni0.95Al0.05O4.025+δ (LNAO) in isothermal conditions are investigated and ionic charge of transport (αi ∗), which is a measure of cross-effect between ionic and electronic flows and corresponds to the number of electrons dragged by a cation in the absence of the direct cause of electron flow, and partial electronic conductivity under a blocking condition (σ′e) is measured and values of Onsager transport coefficients are extracted by constructing an Onsager matrix. αi ∗ shows a minimum during its variation with oxygen partial pressure (pO2) which might be related to the unusual defect structure of LNO systems. Oxygen chemical diffusivities (Dchem) as a function of pO2 at different temperatures are extracted from Onsager coefficients to calculate defect diffusivity of interstitial oxygen (Di) and oxygen self-diffusivity(DO). Di values for LNAO are nearly 2 orders of magnitude lower than those for LNO, which might be due to the reduction in free-volume of perovskite layer on Al3+ doping. Partial ionic conductivity (σi) and oxygen permeation flux (JO2) are calculated from Onsager coefficients, and values are compared with LNO. © 2016 The Electrochemical Society.