[1] The term is usually applied to solid ionic compounds that contain the oxide anion O2− and two or more element cations.
Typical examples are ilmenite (FeTiO3), a mixed oxide of iron (Fe2+) and titanium (Ti4+) cations, perovskite and garnet.The cations may be the same element in different ionization states: a notable example is magnetite Fe3O4, which is also known as ferrosoferric oxide , contains the cations Fe2+ ("ferrous" iron) and Fe3+ ("ferric" iron) in 1:2 ratio.
Other notable examples include red lead Pb3O4, the ferrites,[2] and the yttrium aluminum garnet Y3Al5O12,[3] used in lasers.
Synthetic mixed oxides are components of many ceramics with remarkable properties and important advanced technological applications, such as strong magnets, fine optics, lasers, semiconductors, piezoelectrics, superconductors, catalysts, refractories, gas mantles, nuclear fuels, and more.
Piezoelectric mixed oxides, in particular, are extensively used in pressure and strain gauges, microphones, ultrasound transducers, micromanipulators, delay lines, etc.