An embodiment of an LED lamp that generates light of a color temperature that decreases with decreasing power applied to the LED lamp may include at least one lighting arrangement that may include a first LED array of serially connected first LED chips, a second LED array of serially connected second LED chips; a first photoluminescence layer covering the first LED array for generating light of a first color temperature; a second photoluminescence layer covering the second LED array for generating light of a second different color temperature; and a linear resistor serially connected to the first LED array, wherein the first LED array and second LED array are connected in parallel.

The present disclosure provides a red phosphor powder, a preparation method thereof and a luminescent device comprising the red phosphor powder. The red phosphor powder comprises inorganic compounds containing an element A, an element D, an element X and manganese, wherein element A is one or more selected from a group of Li, Na and K and necessarily includes K; element D is composed of Ge and Si, or element D is composed of Si, Ge and Ti; and element X is one or more selected from a group of F, Br and Cl and necessarily includes F; and the inorganic compound has the same space group structure as K.sub.2GeF.sub.6, the space group structure being the hexagonal crystal system P-6.sub.3mc(186). The red phosphor powder has a uniform morphology, a high luminescent efficiency and a good stability.

The present invention addresses providing a novel narrowband red phosphor having a high internal quantum efficiency, a short afterglow time, and a large number of emission components in a short-wavelength region with high red visibility. This is solved by a phosphor characterized by including a crystalline phase that has a predetermined composition and having a specific peak in a powder X-ray diffraction pattern.

A semiconductor nanocrystal particle including a transition metal chalcogenide represented by Chemical Formula 1, the semiconductor nanocrystal particle having a size of less than or equal to about 100 nanometers, and a method of producing the same:

M.sup.1M.sup.2Cha.sub.3 Chemical Formula 1 wherein M.sup.1 is Ca, Sr, Ba, or a combination thereof, M.sup.2 is Ti, Zr, Hf, or a combination thereof, and Cha is S, Se, Te, or a combination thereof.

The present invention relates to a method for producing a hexafluoromanganate(IV), said method being characterized by comprising: inserting an anode and a cathode into a reaction solution that contains a compound containing manganese having an atomic valence of less than 4 and/or manganese having an atomic valence of more than 4 and hydrogen fluoride; and then applying an electric current having an electric current density of 100 to 1000 A/m.sup.2 between the anode and the cathode. According to the present invention, it becomes possible to produce a hexafluoromanganate(IV) in which the content ratio of manganese having an atomic valence of 4 is high and the contamination with oxygen is reduced and which has high purity. When a complex fluoride red phosphor is produced using the hexafluoromanganate(IV) as a raw material, the phosphor produced has high luminescence properties, particularly high internal quantum efficiency.

The invention relates to a material represented by the following formula (I)

(M).sub.8(MM).sub.6O.sub.24(X,X).sub.2:M

formula (I).

Further, the invention relates to a luminescent material, to different uses, and to a device.

Provided is a method for producing a phosphor having a chemical composition represented by formula (I), A.sub.2MF.sub.6:Mn (I) (A is one type or more of an alkali metal selected from Li, Na, K, Rb, and Cs, and includes at least Na and/or K, and M is one type or more of a tetravalent element selected from Si, Ti, Zr, Hf, Ge, and Sn.), the method comprising preparing a first hydrofluoric acid solution containing M and a second hydrofluoric acid solution containing A as well as either dissolving a compound containing Mn in either the first hydrofluoric acid solution or the second hydrofluoric acid solution or preparing a separate solution in which the compound containing Mn is dissolved. When the solutions are mixed to precipitate the phosphor of the formula (I), the solutions are mixed so that the concentration of M is 0.1 to 0.5 mol/liter when all the solutions are mixed. According to the present invention, a complex fluoride phosphor having excellent luminescence properties can be produced stably with high yield.

A coated phosphor comprises phosphor particles, wherein said phosphor particles comprise manganese-activated complex fluoride phosphors; and a coating on individual ones of said phosphor particles, said coating comprising a layer of carboxylic acid material encapsulating the individual phosphor particles.

A method of increasing the luminescence efficiency of titanium-doped oxide crystal, used as a laser material, is disclosed. This is accomplished by tempering the crystal at a temperature from 1750 C. to 50 C. below the melting point of the oxide crystal in a hydrogen protecting atmosphere with a constant partial pressure of the aluminium suboxide Al.sub.2O gas. By applying the method of the present invention, its luminescence efficiency of titanium-doped oxide crystal increases by 10 to 50 percent, and possibly by as much as 100 percent or more compared to previous technological treatments.

A process for preparing a population of coated phosphor particles is presented. The process includes combining particles of a phosphor of formula I: A.sub.x[MF.sub.y]:Mn.sup.4+ with a first solution including a compound of formula II: A.sub.x[MF.sub.y] to form a suspension, where A is Li, Na, K, Rb, Cs, or a combination thereof; M is Si, Ge, Sn, Ti, Zr, Al, Ga, In, Sc, Hf, Y, La, Nb, Ta, Bi, Gd, or a combination thereof; x is an absolute value of a charge of the [MF.sub.y] ion; and y is 5, 6 or 7. The process further includes combining a second solution including a source A.sup.+ ions with the suspension.