Europium is among the most chemically reactive and most chemically reactive of the rare earths and the most efficient luminescent emitters, and its value lies almost entirely in phosphors and nuclear energy. Europium ions emit vivid red light and highly efficient blue light under ultraviolet or blue excitation, which is why it has been an indispensable activator in trichromatic phosphors ever since the color-television tube era: trivalent europium gives the characteristic red emission, divalent europium the characteristic blue, and together with green emission from terbium or cerium they form the trichromatic fluorescent lamps and white LEDs. The modern lighting and display industry's demand for high-color-rendering, high-efficiency white light essentially cannot be met without these two europium phosphors. In banknote anti-counterfeiting, europium-based fluorescent patterns printed on notes such as the euro become visible under ultraviolet light, an important security feature. On the nuclear side, europium-151 has an extremely high thermal-neutron absorption cross-section and is made into control rods and burnable poisons used for reactor power regulation and shutdown.
Eu2O3 (europium(III) oxide) is the principal industrial oxide of europium. It is a near-white powder with a faint pink tinge, and is the precursor for preparing red and blue phosphors, as well as the feedstock for rare-earth glass additives and reactor neutron-absorbing materials. EuCl3 (europium trichloride) is an intermediate in the extraction and separation flowsheet; reduction yields divalent europium compounds, and it is also used in research and in the synthesis of luminescent materials. The so-called europium-activated blue phosphor generally refers to the divalent-europium-activated barium magnesium aluminate phosphor (BAM, BaMgAl10O17:Eu2+), which provides efficient blue light in trichromatic energy-saving lamps and LCD backlight tubes; the trivalent-europium-activated yttrium oxide red phosphor (Y2O3:Eu3+), for its part, is the most classic red component in trichromatic lamps and white LEDs, and was also used in plasma displays and long-persistence afterglow materials.
