<p>Employing a self-designed temperature-control device for sapphire substrate polishing, the influence of external thermal fields on chemical mechanical removal mechanisms at the polishing pad/sapphire interface was investigated through combined simulation and experimental approaches. Molecular dynamics simulations were employed to investigate the chemical reactions between amorphous SiO₂ and sapphire substrates under hydrothermal conditions. The diamond/SiO₂ core-shell abrasives were prepared through an optimized sol-gel process, and the amorphous SiO₂ shell (10&#xa0;nm thick) was densely coated on the diamond surface. The microstructure and morphology of diamond abrasive, synthetic diamond/SiO₂ core-shell abrasives, and SiO₂ abrasives were characterized by FESEM and TEM. Sapphire substrates were polished at different temperatures, using three different types of abrasives, respectively. The material removal behavior of diamond/SiO₂ core-shell abrasives under thermally assisted semi-fixed abrasive polishing was discussed via analyzing the polished wear debris. Outcomes of an experiment indicated that the core-shell abrasives enabled the sapphire substrate to obtain a scratch-free surface with a 29.6% reduction in surface roughness, as well as a 179% increase in material removal rate, when the polishing interface temperature was set to 50&#xa0;°C compared to conventional diamond abrasives polishing at room temperature. The wear debris characteristics demonstrated that sustained solid-state chemical interactions between abrasives and the substrate were enhanced through thermal assistance, thereby facilitating the formation of the soft reaction layer (AlOOH and Al₂Si₂O₇). This study clarifies the chemo-mechanical synergy of core-shell abrasives in thermally assisted polishing, offering foundations for sapphire ultra-precision machining optimization.</p>