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 Researchers devise microreactor to study formation of methane hydrate
23.08.2017 | NYU Tandon School of Engineering

nachricht Meter-sized single-crystal graphene growth becomes possible
22.08.2017 | Science China Press

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

What the world's tiniest 'monster truck' reveals

23.08.2017 | Life Sciences

Treating arthritis with algae

23.08.2017 | Life Sciences

Witnessing turbulent motion in the atmosphere of a distant star

23.08.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>