To investigate the effect of dislocations on grain growth in polycrystals, two sets of experiments were performed by using SrTiO3 single crystals and SrTiO3 powder compacts. In the first set, with single crystals embedded in 2.0mol%TiO2 excess powder compacts, the growth of the single crystal was not affected by dislocations at 1300C, below the eutectic temperature, while it was enhanced by dislocations at 1470C, above the eutectic temperature, where the grain boundaries were wetted by an amorphous phase. In the second set, with 0.5mol%Nb2O5-doped powder compacts, the single crystal grew considerably into the SrTiO3 matrix grains in the presence of an amorphous film between the grains at 1470C both in 95N2-5H2 and in air, similar to the case of the TiO2 excess samples. However, when annealed at 1470C in 95N2-5H2 after pre-annealing at 1250C in 95N2-5H2, the amorphous phase remained at triple junctions and did not penetrate the grain boundaries, implying that this boundary configuration also was thermodynamically stable above the eutectic temperature. In this case, growth of the embedded single crystal was insignificant in spite of the presence of dislocations. These experimental observations indicated that the growth of SrTiO3 was promoted by dislocations only when an intergranular amorphous film was present at grain boundaries. The apparent ineffectiveness of dislocations on grain growth promotion without an intergranular amorphous film was explained in terms of a low fraction of facetted grain boundaries and grain boundary drag by triple junctions.

Intergranular Amorphous Films and Dislocations-Promoted Grain Growth in SrTiO3. S.Y.Chung, S.J.L.Kang: Acta Materialia, 2003, 51[8], 2345-54