Catalytic converters
Carbon arc-lights lamps
Fluorescent tubes

Commercially, ceric oxide is the most important form of cerium. There are also many other applications in which mixtures of cerium, lanthanum, neodymium, and other rare earths are used. These mixtures may be of the form of metallic alloys, mixed oxides or mixed halides, etc.

Ceric oxide is used to polish glass, especially precision optical glasses. It is superior to rouge, in that it polishes glass much quicker. Because of its oxidizing power, cerium is used in glass which is subjected to alfa, gamma, x-ray, light and electron radiation. The cerium decreases the rate of discoloration in glass, primarily by preventing divalent iron from forming, i.e. oxidizes Fe(II) to Fe(III). This is especially useful in TV tubes, where electron radiation could cause the glass to discolor and destroy the color quality of the TV picture. Cerium dioxide is also used to opacify enamels, photochromic glasses, ceramic coatings, refractory oxides, phosphorus, cathodes, capacitors and semiconductors, and as catalyst.

Because of cerium's low nuclear cross section, cerium dioxide is used as diluent in uranium, plutonium or thorium oxide nuclear fuels.

The most common form of cerium-rare earth alloys is known as mischmetal, and it contains about 50% of cerium, 25% of lanthanum, 18% of neodymium, 5% of praseodymium and 2% other rare earths. It is produced in tonnage quantities by the fused salt electrolysis of a mixture of anhydrous chloride of rare earth element derived from monazite or bastnasite. An increase in the high temperature strength and creep resistance is noted by mischmetal additions to magnesium alloys. It is also reported to increase the strength of aluminum, the oxidation resistance of nickel and nickel alloys, and the hardness of copper with only a slight decrease in the electrical conductivity of the copper.

A 30% iron, 70% mischmetal is a common alloy used as lighter flints. The desirable pyrophoric properties of this alloy are due primarily to the cerium.

Cerium is also used as getter in vacuum tubes and as diluent in plutonium nuclear fuels.

Mixed oxides and fluorides containing cerium are used as cores for carbon arcs. The rare earth mixture increases the intensity about tenfold while improving color balance of this white light. The mixed ceric-rare earth oxides are also used as catalysts for cracking petroleum, as polishing materials and waterproofing agents, and fungicides in textile manufacturing.