Progress in discovery and structural design of color conversion phosphors for LEDs

Recent research in the field of phosphor and scintillator materials and related detectors is reviewed. After a historical introduction the fundamental issues are explained regarding the interaction of x-ray radiation with a solid state. Crucial parameters and characteristics important for the performance of these materials in applications, including the employed measurement methods, are described. Extended description of the materials currently in use or under intense study is given. Scintillation detector configurations are further briefly overviewed and selected applications are mentioned in more detail to provide an illustration.

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Scintillation detectors for x-rays

A collapsible ultrasonic reflector incorporates a gasfilled reflector balloon (50), a liquid-filled structural balloon (28) and an ultrasonic transducer (20) disposed within the structural balloon. Acoustic energy emitted by the transducer is reflected by a highly reflective interface between the balloons. In a cardiac ablation procedure, the ultrasonic energy is focused into an annular focal regions (44) to ablate cardiac tissue extending in an annular path along the wall. Devices for stabilizing the balloon structure and for facilitating collapse and withdrawal of the balloon structure are also disclosed.

Thermal treatment methods and apparatus with focused energy application

A multilayer polymer film has an optical stack including a plurality of alternating polymer layers with skin layers having mechanical, optical, or chemical properties differing from those of the layers in the optical stack. In one embodiment, the multilayer polymeric film has one or more holograms that provide attractive and useful optical effects.

Multilayer polymer film with additional coatings or layers

Stable and efficient phosphor systems for white light-emitting diodes (LEDs) are highly important with respect to their application in solid-state lighting beyond the technical limitations of traditional lighting technologies. Therefore, inorganic solid-state conversion phosphors must be precisely selected and evaluated with regard to their special material properties and synergistic optical parameters. In this perspective, we present an overview of the recent developments of LED phosphors; firstly, general photoluminescence-controlling strategies for phosphors to match LED applications have been evaluated; secondly, state-of-the-art and emerging new LED phosphors have been demonstrated. Then, methodologies for the discovery of new LED phosphors by mineral-inspired prototype evolution and new phase construction, as well as combinatorial optimization screening, and the single-particle-diagnosis approach, have been analyzed and exemplified. Finally, future developments of LED phosphors have been proposed.

Recent developments in the new inorganic solid-state LED phosphors

A multilayer film for coating an exterior of a scintillation detector bar includes a pressure sensitive adherent layer containing a percentage of a light-diffusing material therein for affixing to an external surface of the bar. A clear plastic layer separates the adherent layer from a specularly reflecting layer. A protective layer is disposed atop the specularly reflecting layer. The light-diffusing material and the specularly reflecting layer cooperate to retain light within the bar, direct light in random directions within the bar and block optical crosstalk between adjacent bars. A preform consisting of a single piece of film may be used for covering five sides of the bar.

Reflective coating for solid-state scintillator bar

A lighting apparatus capable of emitting white light includes a semiconductor light source; and a phosphor material radiationally coupled to the light source. The phosphor material includes a color-stable Mn+4 doped phosphor prepared by a process including providing a phosphor of formula I; Ax[MFy]:Mn+4 I and contacting the phosphor in particulate form with a saturated solution of a composition of formula II in aqueous hydrofluoric acid; Ax[MFy]; II wherein A is Li, Na, K, Rb, Cs, NR4 or a combination thereof; M is Si, Ge, Sn, Ti, Zr, Al, Ga, In, Sc, Y, La, Nb, Ta, Bi, Gd, or a combination thereof; R is H, lower alkyl, or a combination thereof; x is the absolute value of the charge of the [MFy] ion; and y is 5, 6 or 7. In particular embodiments, M is Si, Ge, Sn, Ti, Zr, or a combination thereof.

Color stable manganese-doped phosphors

The image quality of computed tomography (CT) medical scanners is extremely sensitive to afterglow, radiation damage and optical non-uniformities of scintillators used in X-ray detectors. This represents a tough challenge in the design of scintillator materials with optimum properties. Discussion will center on the development and properties of the first commercialized transparent ceramic scintillator, the (Y,Gd)2O3:Eu-based HiLightTM scintillator used in GE Medical System's CT products. The flexibility of the ceramic scintillator platform has enabled it to be engineered to satisfy the changing needs of CT imaging, which is demonstrated by its successful incorporation into over 8000 CT systems worldwide since 1988. The ceramic process makes possible uniform co-doping at ppm levels to control electronic defects responsible for afterglow, reducing it to levels below detectibility in CT images. Annealing of the material in controlled oxygen atmospheres, combined with rapid oxygen diffusion along grain boundaries in the ceramic, reduces radiation damage to negligible values. Transient thermoluminescence of these materials will be discussed as a diagnostic of electronic trap levels responsible for both afterglow and radiation damage. Finally, with the increased scan speed requirements of modern CT systems, energy transfer between the Eu activator and other rare-earth ions can be used to speed the radiative decay of the scintillator, ensuring the material's continued viability in future CT systems.

Development of the HiLightTM scintillator for computed tomography medical imaging

A phosphor material contains encapsulated particles of manganese (Mn4+) doped fluoride phosphor. A method of encapsulating such particles is also provided. Each particle is encapsulated with a layer of a manganese-free fluoride phosphor. The use of such a phosphor material in a lighting apparatus results in improved stability and acceptable lumen maintenance over the course of the apparatus life.

Robert Joseph Lyons

Papers

Reflective coating for solid-state scintillator bar

Color stable manganese-doped phosphors

Development of the HiLightTM scintillator for computed tomography medical imaging

Moisture-resistant phosphor and associated method

Blue Light-Emitting Diode Phosphors Based upon Oxide, Oxyhalide, and Halide Hosts