A method of synthesizing uranium dioxide crystals. The method of synthesizing includes combining a uranium-based feedstock with a mineralizer solution. The uranium-based feedstock is selected from uranium dioxide, uranium tetrafluoride, uranium tetrachloride, triuranium octoxide, and uranium trioxide. The feedstock and mineralizer solution are pressurized, and then a thermal gradient is applied thereto such that a first portion of the feedstock and the mineralizer solution is heated to a temperature that is greater than a temperature of a second portion of the feedstock and the mineralizer solution. The uranium nutrient enters the mineralizer solution from the feedstock in the first portion and uranium nutrient precipitates to spontaneously form crystals in the second portion.

A method for producing a fluorescent material can be provided. The method includes preparing fluorescent material particles that contain a fluoride having a composition including Mn, at least one selected from the group consisting of alkali metal elements and NH.sub.4.sup.+, and at least one selected from the group consisting of Group 4 elements and Group 14 elements; causing at least one cation selected from rare-earth elements and a phosphate ion to come into contact with each other in a liquid medium containing the fluorescent material particles to obtain rare-earth phosphate-adhered fluorescent material particles including the fluorescent material particles to which the rare-earth phosphate is adhered; and separating the rare-earth phosphate-adhered fluorescent material particles from the liquid medium.

A method of synthesizing alkali uranium fluorophosphate crystals. The method includes combining a uranium-based feedstock with a mineralizer solution. The mineralizer solution includes an alkali nutrient, a phosphate, and a fluoride. The feedstock and mineralizer solution are pressurized and a thermal gradient applied thereto such that a first portion of the feedstock and the mineralizer solution is heated to a temperature that is greater than a temperature of a second portion of the feedstock and the mineralizer solution. Uranium nutrient enters the mineralizer solution from the feedstock in the first portion and uranium nutrient precipitates to spontaneously form crystals in the second portion.

An exemplary embodiment provides for a source of white light having at least one white light emitting device composed of a transparent glass/quartz chamber, a vacuum chamber including an optically active element, a spacer, a focusing lens, an IR laser diode, where the optically active element arranged in the vacuum chamber is a thin-layer oxide matrix doped with rare earth ions selected from the group of Nd, Yb, the concentration of dopant ions being in the range of 0.0001 to 100 at %.

A uranium-based phosphor selected from (i) phosphors having formula I or II:

##STR00001##

where the phosphor having formula I or II is doped with an activator ion including Pr.sup.3+, Sm.sup.3+, or mixtures thereof, where 0a1, 0b1, 0.75x1.25, 0.75y1.25, 0.75z1.25, 2.5p3.5, 1.75q2.25, and 3.5r4.5; (ii) a phosphor having formula I or II, where the phosphor having formula I or II is doped with an activator ion selected from Eu.sup.3+, Pr.sup.3+, Sm.sup.3+, and mixtures thereof; and a counter ion comprising one or more alkali metal ions; and (iii) phosphors having formula III

##STR00002##

where the phosphors having formula III are doped with an activator ion selected from: Eu.sup.3+, Pr.sup.3+, Sm.sup.3+, and mixtures thereof, where A is Li, Na, K, Rb, Cs, or a combination thereof.