Lead scandium tantalate (PbSc(0.5)Ta(0.5)O(3), or PST) ceramics with the addition of 0.5-10 wt% excess PbO were fabricated by the hot-pressing method. The percent of perovskite PST and the long-range order parameter S were quantitatively characterized by X-ray diffraction analysis. The grain size was measured by scanning electron microscopy. The dielectric and pyroelectric behavior under dc bias were investigated from -20 degrees to -50 degrees C. The relationships among dielectric constant, Curie temperature, and dc bias were analyzed by fitting to the Gibbs free energy formulas. Based on these data, the pyroelectric figures of merit F(d) as a function of field and temperature were calculated, and the highest F(d) of 15 x 10-5 Pa-1/2 was obtained under 700 V/mm in the sample with 5 wt% excess PbO.