Protonic Conduction in the BaNdInO 4 Structure Achieved by Acceptor Doping

ZHOU, YU; SHIRAIWA, MASAHIRO; NAGAO, MASANORI; FUJII, KOTARO; TANAKA, ISAO; YASHIMA, MASATOMO; BAQUE, LAURA; BASBUS, JUAN F.; MOGNI, LILIANA V.; SKINNER, STEPHEN J.

CHEMISTRY OF MATERIALS

AMER CHEMICAL SOC

Lugar: Washington; Año: 2021 vol. 33 p. 2139 - 2146

0897-4756

The potential of calcium-doped layered perovskite compounds, BaNd1−xCaxInO4−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, BaNdInO4. The highest total conductivity of 2.6 × 10−3 S cm−1 was obtained in the BaNd0.8Ca0.2InO3.90 sample at atemperature 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% H2O) was 1.3 × 10−4 S cm−1. The incorporation of water vapor decreased the activation energies of the bulk conductivity of the BaNd0.8Ca0.2InO3.90 sample from 0.755(2) to 0.678(2) eV in air. The saturated BaNd0.8Ca0.2InO3.90 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 decreasein the resistance of the x = 0.2 sample, we conclude that experimental evidence indicates that BaNd1−xCaxInO4−x/2 is a fast proton conductor.