Why is cerium oxide the workhorse of rare earth polishing powders for glass and semiconductor CMP?

Why is cerium oxide the workhorse of rare earth polishing powders for glass and semiconductor CMP?
Cerium oxide dominates precision polishing despite being softer than alumina, zirconia, or silica. Its advantage is chemical, not mechanical: oxygen vacancies in the CeO2 lattice drive a chemical-mechanical synergy that makes it the powder of choice for silica-based materials such as silicate glass, quartz, and silicon nitride. In practice, higher-purity grades deliver greater cutting power and longer slurry life, which matters most in long-cycle polishing of hard glass and quartz optical lenses. Applications span flat panel displays, optical lenses, IC photomask substrates, and high-density disk substrates. For buyers, purity grade and particle size distribution are the decisive specification levers, not headline price alone.