In the big family of rare earth elements, cerium is undoubtedly the "big brother". Firstly, the total abundance of rare earths in the crust is 238ppm, of which cerium is 68ppm, accounting for 28% of the total rare earth composition, ranking first; Secondly, cerium is the second rare earth element discovered 9 years after the discovery of yttrium (1794).

        In 1803, Swedish chemist J.J. Berzelius and his teacher W.Hisinger discovered a new element called cerium earth, which had properties very similar to but completely different from yttrium earth, while analyzing the Tungsten mine produced in Sweden (meaning "heavy stone"). In their discovery report, they named it Cemm (cerium) to commemorate the discovery of the asteroid Ceres in 1801.

        Strictly speaking, the initially discovered "cerium" can only be considered as an enriched substance of decoration, or a light rare earth mixed oxide coexisting with lanthanum praseodymium neodymium and other elements. At that time, lanthanum praseodymium neodymium and other elements were still hidden in the "cerium earth" and had not been discovered. However, in any case, among the 17 twin brothers and sisters with similar looks, cerium is the easiest to identify. Because cerium has a significant chemical property, in addition to other rare earth elements that usually exist in a trivalent state, it also exists stably in a tetravalent state. The difference in ionic valence states will inevitably expand the differences in chemical properties, and using this difference can easily separate cerium from adjacent rare earth elements, thus leading to the emergence of chemical methods for cerium extraction. This facilitates the extraction and understanding of cerium by chemists, and coupled with its abundant resources and easy extraction, it is cheaper than other rare earth products, making it the earliest practical rare earth with practical applications.

        However, due to the initial confusion among chemists in the "maze" of constantly discovering new rare earths, it was not until 83 years after the discovery of "cerium earth" that the first use of cerium (also a rare earth) was found as a luminous enhancer for car lampshades. In 1886, Austrian Auer Von Weldach discovered that heating 99% thorium oxide and 1% cerium oxide would emit strong light, which could greatly enhance the brightness of a coal vapor lamp when used as a cover. And in Europe, where electric lights were not yet widespread, steam lamps were the main source of lighting and were crucial for industrial production, commerce, and daily life. Starting from the 1890s, the large-scale production of car lampshade increased the demand for thorium and cerium, effectively promoting the exploration of rare earth deposits worldwide. Large monazite mines were discovered in Brazil and India, which developed into the so-called monazite industry, also known as the early rare earth industry. Although electric lamps gradually replaced gas lamps after World War I, cerium continued to explore new uses.

        In 1903, the second largest use of cerium was discovered by the Austrian Weiersbach, who discovered that cerium iron alloy could produce sparks under mechanical friction and could be used to make flint. The classic use of cerium has a history of 100 years. People who smoke know that lighters use flint, but many people are not familiar with rare earths, let alone know that cerium in them brings fire to people. However, nowadays, flint is facing strong challenges from piezoelectric ceramics, and its production has greatly decreased. During this period, it was also discovered that cerium based alloys (such as Th2dl-RE) can be used as vacuums for electronic devices and vacuum tubes.

        In 1910, the third major use of cerium was discovered, as an arc carbon rod for searchlights and movie projectors. Similar to the lampshade, cerium can improve the visible light conversion efficiency. Searchlights were once an important tool for war air defense. Arc carbon rods were also an indispensable light source for projecting movies.

        The three major uses of cerium mentioned above also represent the early three major uses of rare earths, and it can even be said that the early rare earth industry was entirely based on the development and utilization of cerium's performance. In the early 1950s, China's rare earth industry also started with these three major applications. These uses are all related to luminescence. It can be said that cerium, as an excellent representative of the rare earth element family, has been serving as a "messenger of light" for the benefit of humanity from the beginning.

        Since the 1930s, cerium oxide has been used as a glass decolorizing agent, clarifying agent, coloring agent, and grinding and polishing agent. Cerium dioxide, as a chemical decolorizing agent and clarifying agent, can replace highly toxic white magnets (oxide tablets) to reduce operational and environmental pollution. Cerium titanium yellow pigment can be used as a glass coloring agent to produce beautiful bright yellow art glass. Cerium oxide, as the main component in manufacturing various specifications of polishing powder, has completely replaced iron red polishing powder, greatly improving polishing efficiency and quality. It was originally used for polishing flat glass and eye lenses, but now it is widely used in cathode ray tube (CRT) glass shells, various flat panel displays, optical glass lenses, and computer chips. It is not only a classic use of cerium, but also one of the main application areas of cerium at present. Cerium, as a glass additive, can absorb ultraviolet and infrared rays and has been widely used in automotive glass. Not only can it prevent ultraviolet rays, but it can also lower the temperature inside the car, thereby saving electricity for air conditioning. Since 1997, Japanese automotive glass has been fully decorated with oxide. In 1996, at least 2000 tons of cerium oxide were used for automotive glass, while the United States used over 1000 tons.

        The chemical reactivity of cerium has also enabled him to excel in the field of metallurgy. In 1948, HMomgh, a British man, announced that cerium treatment of cast iron could yield ductile iron. Subsequently, metallurgists discovered that magnesium was an efficient spheroidizing agent for ductile iron, but continued combustion would produce strong magnesium light, and adding magnesium alone would be too intense and unsafe. In the 1950s, the famous Chinese scientist Zou Yuangui successfully studied a unique process of using silicon iron to reduce rare earth containing Baotou blast furnace slag to produce rare earth silicon iron alloys, and then produced rare earth silicon iron magnesium intermediate alloys as spheroidizing agents. This not only overcame the drawbacks of using magnesium alone, but also achieved more stable spheroidizing effects. From then on, the widespread application of rare earth elements in nodular cast iron and vermicular cast iron began. Mixed rare earth metals mainly composed of cerium are also widely used in rare earth treatment of steel (deoxidation, desulfurization, denaturation), rare earth electrical aluminum, and rare earth cast magnesium alloys (purification modification, grain refinement, alloying) and other metal materials.

        Cerium is also used as an excellent environmentally friendly material, with the most representative application currently being automotive exhaust purification catalysts. Adding cerium to commonly used ternary catalysts of precious metals (platinum, rhodium, palladium, etc.) can improve catalyst performance and reduce the amount of precious metals used. The main pollutants in automotive exhaust are carbon monoxide, hydrocarbons, and nitrogen oxides, which can affect human hematopoietic function, form photochemical toxic smoke, and produce carcinogens, causing damage to humans, animals, and plants. The ternary purification catalytic technology can fully oxidize hydrocarbons and carbon monoxide to produce carbon dioxide and water, and decompose nitrogen oxides into nitrogen and oxygen (hence the name ternary catalysis). Platinum, rhodium, palladium and other precious metals are excellent catalytic materials for tail gas purification. However, their high prices and high requirements for both engines and gasoline have limited their widespread application. Adding cerium to the catalyst can significantly reduce the amount of precious metals used and improve catalytic performance, resulting in a significant decrease in the cost of the catalyst. In the United States, automotive exhaust purification catalysts have become the largest consumer of rare earths. Cerium oxide can also be used as a photocatalyst with nano titanium oxide for antibacterial ceramics and oxygen rich ion environmentally friendly coatings.

        Cerium sulfide can replace metals such as lead and cadmium, which are harmful to the environment and humans, as a plastic red coloring agent, and can also be used in industries such as coatings, inks, and paper. The French company Rodier currently possesses leading technology. Organic compounds such as cerium rich light rare earth naphthenates are also used as paint drying agents, PVC plastic stabilizers, and MC nylon modifiers. They can replace toxic substances such as lead salts and reduce expensive materials such as drilling salts.

        Cerium is also used to manufacture many special functional materials, such as fluorescent grade ceria used in the production of green powder (CeMgA111O19: Tb3+) for tricolor fluorescent powders for lamps; The Ce: LiSAF laser system solid-state laser developed in the United States can be used to detect biological weapons and also in medicine by monitoring tryptophan concentration. Metal cerium can be used to manufacture cerium drill copper iron permanent magnet materials; Cerium pigeon electrodes can replace radioactive thorium pigeon electrodes, and so on.

        The use of cerium based light rare earths as plant growth regulators can improve crop quality, increase yield, and enhance crop stress resistance. As a feed additive, it can improve the egg production rate of poultry and the survival rate of fish and shrimp farming, as well as improve the wool quality of long haired sheep. Cerium is a low toxicity substance known in a rare earth book in the United States. Feeding experiments on mice have shown that the oral toxicity of light rare earth oxides rich in cerium is equivalent to oral salt. So far, no endemic diseases caused by rare earths have been found in areas rich in rare earth minerals. Chinese scientists believe through extensive experimental research that rare earth agriculture does not produce environmental pollution and does not pose a threat to the survival of humans and animals.

        Looking at the history of the application and development of cerium, we have reason to believe that cerium, as the most abundant and inexpensive rare earth element in nature, has not only made brilliant contributions to humanity in the past and present, but will also play an increasingly important role in our modernization construction today and in the future.