Glass-Like Thermal Conductivity of (010)-Textured Lanthanum-Doped Strontium Niobate Synthesized with Wet Chemical Deposition

We have measured the cross‐plane thermal conductivity (κ) of (010)‐textured, undoped, and lanthanum‐doped strontium niobate (Sr2−xLaxNb2O7−δ) thin films via time‐domain thermoreflectance. The thin films were deposited on (001)‐oriented SrTiO3 substrates via the highly‐scalable technique of chemical solution deposition. We find that both film thickness and lanthanum doping have little effect on κ, suggesting that there is a more dominant phonon scattering mechanism present in the system; namely the weak interlayer‐bonding along the b‐axis in the Sr2Nb2O7 parent structure. Furthermore, we compare our experimental results with two variations of the minimum‐limit model for κ and discuss the nature of transport in material systems with weakly‐bonded layers. The low cross‐plane κ of these scalably‐fabricated films is comparable to that of similarly layered niobate structures grown epitaxially.