We obtained single-crystal YBa2Cu3O7-δ and ErBa2Cu3O7-δ platelets by eutectic growth from CuO-rich mixtures of Y2O3 (or Er2O3), BaCO3, and CuO. Ground and mixed powders were loaded in an alumina crucible and heated to 1150–1180°C in air, held for 0.5-2 h, then cooled under programmed temperature and time conditions. Individual crystals of both YBa2Cu3O7-δ and ErBa2Cu3O7-δ up to 4 mm wide have been grown in voids that form in the charge. Similarly, compositions and temperature programs that allow single-crystal growth of Bi-Sr-Ca-Cu-O platelet crystals up to 4 mm wide that resembled mica in their delamination tendency were found. Low field AC magnetic susceptometry was used to characterize the temperature dependence of the superconducting transition in small single crystals of the three superconductors. Both the real χ′ and imaginary χ′' components of magnetic susceptibility were measured.