Description:
Reference #: 00969
Background:
Research in solid-state lighting and in particular on new phosphor materials for white-light emitting diodes (LEDs) has become vitally important, because it can provide substantial energy savings and reduce global environmental impact. Phosphors are materials capable of emitting photoluminescence when excited by radiation. They are used in LEDs, cathode ray tubes (CRT) and sensors. LEDs are extensively used for applications in industrial and domestic lighting, indicator lights, traffic signs, automotive dashboards, and portable flash lights. Phosphors for lighting applications can be made in two ways: doping with activator ions or self-activation.
Disadvantages associated with the use of existing phosphors such as sulfides, nitrides and fluorides triggered the search for other materials among them oxyfluorides with photo-luminescent properties. For example Sulfide based phosphors are not very stable chemically when exposed to air and humidity and some undergo strong thermal quenching. Another disadvantage of sulfide based phosphors is that corrosive emissions of H2S gas can occur as a decomposition byproduct. Although nitride and/or oxynitride, e.g. Sr2Al2Si10N14O4:Eu2+ based phosphors have high efficiencies and chemical as well as thermal stability, these materials need to be prepared under complex synthesis conditions. Similarly, some Fluoride phosphors doped with Yb3+, Er3+, Tm3+ are not very stable materials in air and humidity.
Invention Description:
This invention uses oxyfluoride NaCa2GeO4F has potential as a phosphor for LED based lighting applications. Analysis of X-ray powder diffraction data has shown that this oxyfluoride NaCa2GeO4F possesses an anion ordered structure containing closely packed fluorine centered face sharing octahedra. Apart from the fact that it demonstrates stability in air and humidity, it’s Ce3+ and Eu2+ activated compounds emits in the 500-600 nm range at 410-465 nm excitations.
Potential Applications:
LEDs are extensively used for applications in industrial and domestic lighting, indicator lights, traffic signs, automotive dashboards, and portable flash lights. Phosphors for lighting applications can be made in two ways: doping with activator ions or self-activation.
Advantages and Benefits:
1. This oxyfluoride [NaCa2GeO4F] is chemically very stable. It is a more stable compound than fluorides with respect to hydrolysis
2. Compared to the other phosphors, thermal quenching is reduced
3. The presence of fluorine in the structure positively affects the photoluminescence properties of the phosphor