Phosphor

As a general fluorescent solids are referred to, the produce visible light by excitation with light of short wavelength to the ultraviolet or electron bombardment. The designation phosphors (plural ) is derived from the English word for phosphorus fluorescent from. The term light - " phosphorus ", however, is misleading because phosphors contain no elemental phosphorus. The correct term for phosphors is the word luminophore used in Russian and French speaking countries.

Basics

The luminous phenomena are based on the fluorescence (immediate light emission at short wavelength light), the phosphorescence ( delayed light emission by short wavelength light) and cathodoluminescence ( light emission during electron bombardment ), sometimes the electroluminescence in electric fields.

Inorganic phosphors are often crystalline materials which provide an industrially useful light output in the crystal structure by selectively introducing an impurity. This degree of purity of the starting materials of up to 99.9999 % is required. The phosphors are generally based on oxides or sulfides, such as zinc oxide, zinc sulfide, zinc cadmium sulfide, and zinc sulphide selenide, and silicates such as willemite and Zinkberylliumsilicat. Zinc sulfide is used in self-luminous radioactive luminous colors.

The doping element determines the light color, such as

• ZnS: Mn → orange
• ZnS: Ag → blue
• ZnS: Cu → Green
• ZnS: Ln → depending on the lanthanide red to blue- green

Important doping and base elements are the lanthanides europium ( Eu) and terbium (Tb ), europium (III ) -doped Y2O2S used in color picture tubes the red phosphor, Eu3 doped Y2O3 produced in energy -saving lamps and other fluorescent gas discharge lamps, the red spectral component. Terbiumdotiertes gadolinium oxide sulfide Gd2O2S was used as a green phosphor in radar screens.

Parameter, such as light color of fluorescence and phosphorescence, afterglow time, and efficiency of energy reproduction are not only dependent on the materials used, but also on the processing such as annealing, grinding, quenching, atmospheric conditions during these operations.

Applications

• Screen coating on the cathode ray tube (CRT) in television sets, oscilloscopes, monitor ( cathodoluminescence )
• Internal coating of fluorescent lamps and tubes for the colors white and other colors ( fluorescent )
• Coating of ultraviolet and blue LEDs, to obtain bright white LEDs.
• Fluorescent colors ( safety clothing, highlighter ): these lights using (fluorescence ) of the blue portion in the daylight
• Security features on banknotes and securities by excited fluorescence.
• Fluorescent markers to study biological processes by means of excitation by ultraviolet, such as fluorescein

Further light -emitting solid substances are generally not referred to as a phosphor to the principles of the light-emitting luminance and light emitting color, see below.