Introduction of phosphors for electric light sources

After the development of high-pressure and low-pressure mercury lamps in the 1930s, there was a need for specialized luminescent materials to effectively convert the ultraviolet light generated by these two types of discharges into visible light.

Many materials in nature can emit light under external influences. Luminescence is the process by which energy absorbed within an object is converted into light radiation. Luminescent materials emit light under external influences, which we call excitation. Based on the method of excitation, they are classified into photoluminescence, electroluminescence, cathodoluminescence, and so on.

Many objects in nature (solids, liquids, and gases) possess luminescent properties. Solid luminescent materials fall into two categories: organic and inorganic. Luminescent materials used in electric light sources are coated on a glass tube (shell) and must undergo a specific heat treatment. These factors limit the selection of materials to solid inorganic compounds.