“…Layered perovskites with general formula AA′BO 4 where A is Ba or Sr, A′ is La or Nd, and B is In or Sc were described as ionic (oxygen-ionic and protonic) conductors in the past few years [ 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 ]. It was proved that doping in the cationic sublattices is the successful way for improving protonic conductivity up to ~1.5 orders.…”