It is found that ceramic thermoelectret based on Ca5Nb4TiO17 with five-layered slab perovskite-like structure is characterized by high values of potential external electric field VS which demonstrates enchanced stability in time both under normal and high humidity conditions. In particular, the initial value VSo of the surface potential for Ca5Nb4TiO17 polarized ceramics (Fpol. = 15 kV/cm, Tpol. = 493 K, pol. = 2 h) is equal to 480 V, the decreasing of VS/VSo under normal conditions does not exceed 20 % for 316 days and under 100 % of humidity reaches 73 % for 7 days.
