Waste heat can be directly converted into electrical energy by performing the Olsen cycle on pyroelectric materials. The Olsen cycle consists of two isothermal and two isoelectric field processes in the electric displacement versus electric field diagram. This paper reports on the energy harvested by lanthanum doped lead zirconate titanate (8/65/35 PLZT) subjected to the Olsen cycle. The material was alternatively dipped into a cold and a hot silicone oil bath under specified electric fields. A maximum energy density of 770 J/L per cycle corresponding to a power density of 9.6 W/L was obtained for temperatures between 25 and 160°C and electric fields cycled between 0.2 and 4.5 MV/m.