Electrical conductivity of Zn-doped high temperature proton conductor LaNbO4

• La1 − xZnxNbO4 − δ with various Zn contents was prepared; phase and sintered microstructure were characterized.
• The effect of composition and microstructure on conductivity was evaluated.
• The total conductivity of LaNbO4 was improved obviously by Zn doping.

Zn-doped LaNbO4 (La1 − xZnxNbO4 − δ, LZ100x) was prepared by a solid-state reaction method with x = 0, 0.005, 0.01, 0.015, 0.03 and 0.05 and investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and conductivity measurement. There were no XRD and TEM evidences of formed secondary phases in the composition range of x ≤ 0.03 due to the sensitivity. However, the solubility of Zn, less than 1.0 mol.%, was reasonable, according the variety of the grain sizes, conductivity, as well as the activation energy for the conductivity, with the increasing concentration of Zn. The conductivity of LaNbO4 was improved by one to two orders of magnitude with Zn doping in the research range; and the highest conductivity of 9.8 × 10− 4 S cm− 1 was obtained with LZ0.5 at 900 °C in wet air.