FIELD: materials for electrochemical devices. SUBSTANCE: invention relates to production of materials for electrochemical devices, namely, solid oxide electrolyte materials with proton conductivity based on barium-lanthanum indate (BaLa2In2O7), which can be used as an electrolyte material in proton-conducting solid oxide fuel cells used to generate electric power. The material is barium-lanthanum indate doped with strontium and magnesium has the following composition: BaLa1.9Sr0.1In1.95Mg0.05O6.925. EFFECT: high values of proton conductivity at T < 450°C and pH2O = 2⋅10−2 atm. 1 cl, 4 dwg.