Solid-state reactions occur when solid materials interact with each other to form new compounds without passing through a liquid phase. These reactions typically involve the diffusion of atoms or ions within the solid structures, leading to changes in composition and crystal structure. Common examples include the formation of ceramics and metal alloys. These reactions are essential in various fields, including materials science and chemistry, as they help in synthesizing new materials with desired properties. Understanding solid-state reactions can improve processes in industries such as semiconductors, pharmaceuticals, and energy storage.