Another possible PGEC material

Lead Telluride is a material used as a thermoelectric power generator, with a dimensionless figure of merit, ZT, of about 0.7 at a temperature of 700K. Its thermal conductivity at room temperature is about eight times the value calculated by Slack for the minimum thermal conductivity of PbTe, which is 2.5mW/cm.K. Its crystalline structure is rocksalt, with a lattice parameter of 6.462ÅThere is not enough room between atoms to place a loose atom that can scatter phonons so we need to alter it in order to obtain a Phonon-Glass, Electron-Crystal material. Our idea is to disperse endohedral fullerenes into the lead telluride matrix. The atoms filling these fullerenes can scatter heat-carrying phonons. Given the high dielectric constant of lead telluride, we expect the disturbance to the electrical properties of the material to be minimal. Preliminary calculations of the thermal conductivity of this material indicate that we should be able to reach the minimum thermal conductivity of pure lead telluride with an approximate volume concentration of C_60 in the order of 7%. We shall present results of calculations for several different endohedral fullerenes.