We have found that substitution of bismuth into theTlBa2Ca2Cu3O9system leads to a high temperature superconductor with significantly greater low temperature flux pinning than that of the other copper oxide superconductors. Bi substitutes at the Tl site up to 20 at. &percent;. The superconducting transition temperatureTcincreases from 110 K forx=0.0to 116 K forx=0.2.Scanning electron microscope (SEM) images reveal a platelike morphology which is highly suitable for powder-in-tube processing. The magnetization–hysteresis loop shows that the Bi-substituted phase has significantly better low temperature flux pinning properties than the pristine Tl cuprate, and exhibits only a weak dependence on temperature and field when compared to that of unsubstituted phase. However, at 77 K the compound has lowerJc,determined magnetically, compared to that of the(Tl,Pb,Bi)Sr1.6Ba0.4Ca2Cu3Oyand Y-123 systems. The enhancement of superconducting properties is attributed to an increased coupling between theCuO2planes along thecaxis. Substitution of 20&percent; of Bi inTlBa2Ca2Cu3O9makes the compound an excellent choice for magnet wire applications at relatively low temperatures. ©1997 American Institute of Physics.