Advanced applications of amorphous alumina: From nano to bulk

In modern technologies, the researchers are keen on top-down approaches to tailor the materials from bulk into their nanometer forms. For the amorphous alumina, this is the other way around. The amorphous alumina was receiving attention in the forms of thin films or nanoparticles many years ago, yet any attempts to increase the dimensions destabilized its amorphous structure and caused crystallization at even relatively modest temperatures. This issue has been addressed by smart engineering of its lattice strain, which allows the formation of a high-temperature stable bulk alumina. In this review, we present the recently developed synthetic methods and provide insights in sustaining the amorphous structure of widely used alumina. We highlight its adoptable short-range structure and morphology, emphasize the corresponding tuning of the mechanical and electronic properties, and illuminate the advanced applications in wear and scratch resistant coatings, corrosion protection, insulator layers, capacitor, luminescent material, and catalysis.