Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Single-Crystal Phosphors Suitable for Ultra-Bright, High-Power White Light Sources

31.08.2015

Researchers in Japan successfully developed single-crystal phosphors that use a blue LD (laser diode) as an excitation light source, are suitable for ultra-bright, high-power white lighting, and have outstanding temperature characteristics.

The Optical Single Crystals Group at National Institute for Materials Science (NIMS) led by Group Leader Kiyoshi Shimamura and Senior Researcher E. Garcia Villora, in collaboration with Tamura Corporation (President, Naoki Tamura) and Koha Co., Ltd. (President, Yasuhiro Nakashima), successfully developed single-crystal phosphors (based on (Y1-xLux)3Al5O12 oxide-garnets) that use a blue LD (laser diode) as an excitation light source, are suitable for ultra-bright, high-power white lighting, and have outstanding temperature characteristics.


YAG single-crystal phosphor ingot. Image copyright: NIMS

In line with environmentally conscious efforts to promote power-saving and mercury-free products, white lighting that uses blue LEDs as an excitation light source has grown rapid in popularity in recent years. At the same time, products that use blue LDs as an excitation light source have also been commercialized to meet the needs of certain light-p rojectors and car headlights.

These require a high-brightness that is difficult to attain with LED light sources. Due to its optical properties, LD light can be easily collected with a lens or mirror, and it is feasible to focus 100-watt-equivalent LD light on an area as small as several millimeters in diameter.

However, as the power density of the LD excitation light increases, the heat generated by the lighting device also increases proportionally. The use of conventional phosphors, with low thermal conductivities and a decreasing internal quantum efficiency with the temperature, requires complex cooling techniques and critically limits the applicable LD power. Further, non-oxide based powder phosphors degrade irreversibly with the temperature.

In this study, the developed single-crystal phosphors, grown from the melt by the Czochralski technique, exhibit superior temperature characteristics, overcoming mentioned difficulties. On the one hand, due to the higher thermal conductivity (over two orders of magnitude) they can be cooled much more efficiently, avoiding overheating and enabling downsizing and cost reduction of lighting products.

On the other hand, their quantum efficiency does not drop with the temperature, exhibiting an efficiency over 0.9 till 300 °C in either plate or powder form. These two features, high thermal conductivity and quantum efficiency, are so remarkable that when the emission of conventional phosphors is already quenched by the temperature rise, under the same nominal conditions the temperature of single-crystal phosphors barely increases. Thus, in contrast with conventional powder phosphors, single-crystal phosphors will allow the fabrication of brighter and more powerful lighting products.

Based on this study, we have already acquired two patents in Japan, and have applied for five additional patents in Japan and abroad. We are aiming at stablishing the growth methods for the efficient mass production of single-crystal phosphors for laser lighting products such as laser projectors and laser headlights by the end of FY2015 in collaboration with Tamura Corporation.


Associated links
Original press release from NIMS

Mikiko Tanifuji | ResearchSea
Further information:
http://www.researchsea.com

More articles from Materials Sciences:

nachricht Pressure tuned magnetism paves the way for novel electronic devices
18.12.2018 | Bar-Ilan University

nachricht Researchers observe charge-stripe crystal phase in an insulating cuprate
18.12.2018 | Boston College

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Data storage using individual molecules

Researchers from the University of Basel have reported a new method that allows the physical state of just a few atoms or molecules within a network to be controlled. It is based on the spontaneous self-organization of molecules into extensive networks with pores about one nanometer in size. In the journal ‘small’, the physicists reported on their investigations, which could be of particular importance for the development of new storage devices.

Around the world, researchers are attempting to shrink data storage devices to achieve as large a storage capacity in as small a space as possible. In almost...

Im Focus: Data use draining your battery? Tiny device to speed up memory while also saving power

The more objects we make "smart," from watches to entire buildings, the greater the need for these devices to store and retrieve massive amounts of data quickly without consuming too much power.

Millions of new memory cells could be part of a computer chip and provide that speed and energy savings, thanks to the discovery of a previously unobserved...

Im Focus: An energy-efficient way to stay warm: Sew high-tech heating patches to your clothes

Personal patches could reduce energy waste in buildings, Rutgers-led study says

What if, instead of turning up the thermostat, you could warm up with high-tech, flexible patches sewn into your clothes - while significantly reducing your...

Im Focus: Lethal combination: Drug cocktail turns off the juice to cancer cells

A widely used diabetes medication combined with an antihypertensive drug specifically inhibits tumor growth – this was discovered by researchers from the University of Basel’s Biozentrum two years ago. In a follow-up study, recently published in “Cell Reports”, the scientists report that this drug cocktail induces cancer cell death by switching off their energy supply.

The widely used anti-diabetes drug metformin not only reduces blood sugar but also has an anti-cancer effect. However, the metformin dose commonly used in the...

Im Focus: New Foldable Drone Flies through Narrow Holes in Rescue Missions

A research team from the University of Zurich has developed a new drone that can retract its propeller arms in flight and make itself small to fit through narrow gaps and holes. This is particularly useful when searching for victims of natural disasters.

Inspecting a damaged building after an earthquake or during a fire is exactly the kind of job that human rescuers would like drones to do for them. A flying...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

ICTM Conference 2019: Digitization emerges as an engineering trend for turbomachinery construction

12.12.2018 | Event News

New Plastics Economy Investor Forum - Meeting Point for Innovations

10.12.2018 | Event News

EGU 2019 meeting: Media registration now open

06.12.2018 | Event News

 
Latest News

Pressure tuned magnetism paves the way for novel electronic devices

18.12.2018 | Materials Sciences

New type of low-energy nanolaser that shines in all directions

18.12.2018 | Physics and Astronomy

NASA research reveals Saturn is losing its rings at 'worst-case-scenario' rate

18.12.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>