Amorphous strontium titanate exhibits exceptional thermal and electronic properties critical for advanced semiconductor devices. However, its lattice thermal conductivity as a bulk material has not been reported. Its underlying structural characteristics and thermal transport mechanisms remain unexplored. Herein, we perform Green-Kubo molecular dynamics and Allen-Feldman analysis across 100–1800 K using the neuroevolution potentials trained on ab initio datasets. We report a low thermal conductivity (0.40 ${\mathrm{Wm}}^{-1}{\mathrm{K}}^{-1}$ at 300 K) with conventional glass-like thermal conductivity behavior across the temperature range below its recrystallization onset temperature at 800 K. This low lattice thermal conductivity stems from its structural complexity and dual localization mechanisms present within the amorphous perovskite framework. High-frequency modes confined within the disordered ${\mathrm{TiO}}_6$ polyhedra and a group of low-frequency modes involved Sr atom rattling, collectively enabling up to 29% localized vibrations, which is triple that of a conventional example of amorphous silica. Structural analysis shows contracted Ti-Ti distances and disrupted Sr networks create rattling cages for phonon trapping. Our work establishes atomic-scale design principles for disorder-mediated thermal suppression in perovskite-derived glasses, providing pathways to engineer thermal-insulating materials.

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• Lattice thermal conductivity
• Thermal properties
• Amorphous materials
• Density functional calculations