To understand the thermal conductivity suppression within PGEC titanate oxide thermoelectrics we hope to complement theoretical calculations performed on several perovskites with measurement of phonon dispersions through inelastic neutron scattering. The samples are ready to be measured and have well characterised structures (I11, HRPD) and properties (thermal & electronic transport), published recently. Measurements over a range of temperatures will allow us to probe their anharmonic nature shown by calculations to emerge at 30 K and understand how this influences thermal conductivities of both phonon-crystal and phonon-glass materials. This combination of experiment and theory will provide a new understanding of correlations between electronic and thermal transport within these materials and directly link theoretical calculations with the design and discovery of better thermoelectrics.