Suppressing Thermal Conductivity in SrTiO₃ by Introducing Oxygen Isotope Disorder

Transition metal oxides are promising candidates in the field of thermoelectricity, which can convert heat and electricity into each other and realize the efficient utilization of waste energy. For the figure of merit ZT = S²σT/(κ_e + κ_l), a lower thermal conductivity is desired for an enhanced ZT, and cation doping is an appropriate way to regulate the thermal transport properties. However, because S, σ, and κ_e are strongly coupled with each other, cation doping for one parameter modification can generate compensation with others, making regulation more difficult. In this work, we demonstrate the effective engineering of the thermal conductivity of SrTiO₃ films by partial oxygen isotope substitution with ¹⁸O using a straightforward aftergrowth thermal annealing process. The results show that the isotope disorder promotes the scattering of phonons and generates a nearly 20% decreased thermal conductivity of SrTiO₃ films. Our work provides a convenient new route for the design of thermoelectric materials with high ZT values.