Protonic Conduction in the BaNdInO4 Structure Achieved by Acceptor Doping

摘要

x )Ca_(x )InO_(4–x /2) (where x is the excess Ca content), as protonic conductors was experimentally investigated. The acceptor-doped ceramics exhibit improved total conductivities that were 1–2 orders of magnitude higher than those of the pristine material, BaNdInO_(4). The highest total conductivity of 2.6 × 10~(–3) S cm~(–1) was obtained in the BaNd_(0.8)Ca_(0.2)InO_(3.90) sample at a temperature of 750 °C in air. Electrochemical impedance spectroscopy measurements of the x = 0.1 and x = 0.2 substituted samples showed higher total conductivity under humid environments than those measured in a dry environment over a large temperature range (250–750 °C). At 500 °C, the total conductivity of the 20 substituted sample in humid air (∼3 H_(2)O) was 1.3 × 10~(–4) S cm~(–1). The incorporation of water vapor decreased the activation energies of the bulk conductivity of the BaNd_(0.8)Ca_(0.2)InO_(3.90) sample from 0.755(2) to 0.678(2) eV in air. The saturated BaNd_(0.8)Ca_(0.2)InO_(3.90) sample contained 2.2 mol protonic defects, which caused an expansion in the lattice according to the high-temperature X-ray diffraction data. Combining the studies of the impedance behavior with four-probe DC conductivity measurements obtained in humid air, which showed a decrease in the resistance of the x = 0.2 sample, we conclude that experimental evidence indicates that BaNd_(1–x )Ca_(x )InO_(4–x /2) is a fast proton conductor.>