Enhanced conductivity of lanthanum niobate proton conductor by A and B-site co-doping: Synthesis, phase, microstructure and transport properties

•A cost-effective sol–gel method was used to prepare LaNbO4-based powders.•Dense ceramic was easily obtained with the solution method.•A special strategy of A and B-site co-doping was proposed.•Ca and Sn were separately introduced into La and Nb site.•The co-doped sample exhibited attractive electrical performances.

A cost-effective sol–gel method was successfully developed to synthesize the LaNbO4 based materials. Ca and Sn, occupying the La and Nb sites respectively, were for the first time simultaneously introduced into LaNbO4. Pure phase was obtained at a relatively low temperature and especially the sinterability of LaNbO4 powders prepared by the solution method was considerably improved. Moreover, the Ca and Sn co-doped LaNbO4 ceramic pellet possessed higher conductivity than the previous reports due to more oxygen vacancies and more current carriers. The A and B-site co-doping strategy proposed in the paper offers an effective approach to improve the performances of LaNbO4 as well as other proton conductors.