Rare earth activated rare earth fluorogermanates, represented by the formula: [R.sub.1.sbsb.x R.sub.2.sbsb.(1-x) ].sub.a F.sub.b GeO.sub.C wherein x is a value from about 0.9 to about 0.9998, a is a value of from about 2 to about 4, b is from about 0.85 to about 3.15, c is from about 4 to about 7.5 R.sub.1 is selected from the group of Y, Gd and La and R.sub.2 is selected from Eu, Gd, Tb and Pr and R.sub.1 and R.sub.2 are different, are excited by long or short wavelength ultraviolet light. A solid state process for using a blend of the metal oxides and a heat-decomposable fluorine compound is disclosed along with a preferred embodiment wherein the dual rare earth oxide is formed prior to forming the aforementioned blend of metal oxides.
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a continuation in part of U.S. Patent Application No. 891,072 filed Mar. 29, 1978, now abandoned.
A low-pressure mercury vapor discharge lamp comprising a glass discharge envelope (1) in which during operation of the lamp a discharge is present and which contains mercury and a rare gas, at least a part of the inner wall of the discharge envelope being provided with a thin at least substantially homogeneous continuous transparent layer (4) which is resistent to the action of the discharge. According to the invention, this transparent layer (4) contains an oxide of at least one of the groups comprising yttrium, scandium, lanthanum, gadolinium, ytterbium and lutetium.
The present invention provides a thin film EL device comprising an electrode layer, an emitting layer and an electrode layer formed on a substrate one over another, and an insulating layer interposed between the three layers, the emitting layer containing atoms of a rare-earth element and fluorine atoms in its host material, the atom ratio (F/RE) of the fluorine atoms (F) to the rare-earth atoms (RE) being adjusted to the range of 0.5 to 2.5, and a process for producing the EL device being characterized in that the emitting layer is prepared by forming a film under a condition substantially free from oxygen gas and/or moisture and subjecting the film to a heat treatment at a temperature of 200.degree. C. to 700.degree. C. so that the host material of the emitting layer contains atoms of a rare-earth element (RE) and fluorine atoms (F) in an adjusted atom ratio (F/RE) in the range of 0.5 to 2.5. The present invention affords a thin film EL device which emits, for example, a green luminescence with a high brightness.
Luminescent material having a host lattice comprising, as one of the main constituents, at least one of the elements Y, La and the lanthanides. The material is activated by Gd, and, in addition by one or more of the elements Pb, Tl, Sb, Pr and Bi and comprises one or more of the elements Mn, Tb, Eu, Dy and Sm and the third activator. These materials have an efficient emission originating from the third activator and are used in low-pressure mercury vapour discharge lamps.
