Possibility of grain orientation controlling and activated sintering by thermal diffusion treatment (named heterogeneous sintering) was studied for the superconductive Y₁Ba₂Cu₃O_y ceramics, starting raw materials were mixed powder compacts of Y₂O₃, BaCO₃ and CuO. Heating rate, upper surface temperature, effective temperature gradient, sintering time and cooling rate were approximately, 2K/s, 1240K, 10K/s, 1.8 ks18 ks and 1.4K/s at 750K, respectively; (1) The grains in Y₁Ba₂Cu₃O_y ceramics produced by thermal diffusion treatment were found to be oriented with the c-axis along a heat flow direction, showing a fairly well-oriented grain structure.
(2) Clear differences in temperature dependent electric resistivity between heterogeneously and homogeneously (conventionally) sintered ceramics were recognized as; Critical temperature (Tc^onset)of superconductivity for the sample which was hetrogeneously sintered for 1.8 ks and cooled at 1.4 K/s in air was both 90 K for the A-B plane (perpendicular to a heat flow direction) and the C-plane (parallel to a heat flow direction). Contrary to this, Tc^onset for the sample which was homogeneously sintered under the same condition as the above has never appeared in the temperature range down to 77K of liquid nitrogen temperature.