Thermoelectric (TE) materials enable direct conversion of waste heat into electrical energy. It is a promising area of research, given the current demand for alternative energy technologies to reduce our dependence on fossil fuels. Ceramic oxides are a new and promising class of TE materials because of their high stability at elevated temperatures. Such materials are especially suitable for use in prospective TE power generators because high temperatures are encountered in such operations. This work focuses on pyrochlore ruthenates (A2Ru2O7-x), i.e., lead ruthenate (Pb2Ru2O6.5) and some derivatives, all having defect structures. Pyrochlore ruthenates with Bi, Tl, Y, REE, and Pb, in the A site have been studied widely for their electronic, catalytic and to some extent for their TE properties. TE properties of lead have not yet been studied. The TE properties are characterized by a figure of merit (ZT); ZT=S2σT/κ. S is the Seebeck coefficient, κ thermal conductivity, σ electrical conductivity, and T temperature. Figures of merit depend strongly on κ and S. In this paper we present measurements of κ (RT to 300°C) for lead ruthenate and several derivatives with variable contents of lead in the A- and ruthenium in the B-site, which were prepared by solid-state synthesis and characterized by XRF, X-ray diffraction, SEM/EDX, for composition, structure and phase content.