Materials

New fluorescent lighting phosphors slash use of rare-earth elements

New fluorescent lighting phosp...
Newly-developed phosphors have the potential to reduce the reliance on costly and hard to come by rare-earth elements currently used in fluorescent lighting
Newly-developed phosphors have the potential to reduce the reliance on costly and hard to come by rare-earth elements currently used in fluorescent lighting
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Nerine Cherepy of Lawrence Livermore National Labs (LLNL) displays commercial phosphors (six samples from bottom left of semi-circle) and phosphors being developed by LLNL and collaborators as replacements (five on right)
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Nerine Cherepy of Lawrence Livermore National Labs (LLNL) displays commercial phosphors (six samples from bottom left of semi-circle) and phosphors being developed by LLNL and collaborators as replacements (five on right)
Newly-developed phosphors have the potential to reduce the reliance on costly and hard to come by rare-earth elements currently used in fluorescent lighting
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Newly-developed phosphors have the potential to reduce the reliance on costly and hard to come by rare-earth elements currently used in fluorescent lighting

Phosphors are essential to fluorescent lighting, and thus office parks the world over, but their use of rare-earth elements makes them less than ideal. To address that issue, new types of phosphors have been developed that use substantially less rare-earth elements than current phosphors found in fluorescent bulbs. This could reduce the reliance on the limited supplies of rare-earth elements until fluorescent lighting can be completely replaced by LED lighting, which isn't expected to occur for over a decade.

The inner lining of fluorescent tubes are coated with phosphors, which absorb the ultraviolet light from electrically charged mercury vapor and re-emit visible light based on a mixt of blue, green and red emitters. And while the adoption of LED lighting technology is growing rapidly, there are still about 2.3 billion fluorescent light sockets in the U.S., which will probably continue for the foreseeable future. Fluorescent lights consume over 1,000 tonnes (1,102 tons) of rare-earth oxides each year. Yttrium (Y) oxide is used most, along with europium (Eu), terbium (Tb), cerium (Ce) and lanthanum (La).

These rare-earth elements are expensive and difficult to come by, while their mining can have serious environmental consequences if not managed properly. Some rare-earth elements are relatively abundant, but lack of concentration in ore deposits make them hard to mine. Currently, more than 95 percent of the world’s rare-earth supply is produced in China. Mine slurry tailings can also be mildly radioactive, while toxic acids are used in the refining process

A team of researchers from General Electric, Lawrence Livermore National Laboratory and Oak Ridge National Laboratory working with the Critical Materials Institute (CMI) at Ames Laboratory has now created alternate phosphors that drastically reduce or eliminate two of these five aforementioned rare-earth elements found in fluorescents. They discovered a green phosphor that eliminates lanthanum completely and reduces the terbium content by 90 percent, while a newly-identified red phosphor is rare-earth element-free by eliminating both europium and yttrium. The blue phosphor in current use is already low in rare-earth elements.

Nerine Cherepy of Lawrence Livermore National Labs (LLNL) displays commercial phosphors (six samples from bottom left of semi-circle) and phosphors being developed by LLNL and collaborators as replacements (five on right)
Nerine Cherepy of Lawrence Livermore National Labs (LLNL) displays commercial phosphors (six samples from bottom left of semi-circle) and phosphors being developed by LLNL and collaborators as replacements (five on right)

Except for the lack of rare-earth elements, the new phosphors (five samples on right in above image) are very similar to the ones they’re replacing (six samples from bottom left of semi-circle), according to Nerine Cherepy, lead researcher on the project for Lawrence Livermore Labs.

"The new phosphors include manganese-doped nitrides with zero percent rare earth in its composition," said Cherepy, "and terbium-doped phosphates with reduction critical rare earth content to about 20 percent of what it is in the standard phosphor."

Another issue is cost. The market price for rare earths has fluctuated by more than two-times over the last few years. During the most recent peak in rare earth prices, the cost of fluorescent bulbs roughly doubled.

The new phosphors are on their way to meeting strict requirements, including high efficiency, lamp survivability, precise color rendition and low-cost. Meanwhile, the researchers are assessing the next steps in the phosphors' feasibility for commercial lighting by looking at chemical issues such as slurry compatibility while improving the synthetic process.

Source: Lawrence Livermore National Laboratory

5 comments
windykites
LED array Fluorescent tube replacements fit the same sockets, use less electricity, and last longer, less fragile(no glass), no mercury, so why bother with the old tubes at all?
FollowTheFacts
...fluorescent tubes are being replaced with LED strips already...that's what will happen...this approach has no validity (or desirability)
Don Duncan
Rare earths are not rare, just expensive to mine. Since China can use the dominate position in production (due to low labor costs and lack of environmental law) for political purposes, it behoves the rest of the world to find alternatives. That is best done in a free market. China can't compete with a free market, no govt. can. This is a problem created by controlled markets the world over, and easily solved by a free market. Too bad no free markets exist. The first govt. to adopt a free market, i.e., release their strangle-hold on the market, would enjoy a boom in prosperity exceeding all others, but that would be rational, and governments are not based on reason, they are based on force.
McDesign
Well - all illumination-type LEDs use phosphors to convert the 450nM pump. I wonder if these new phosphors (or similar) will also work with LEDs?
bergamot69
LED will have practically replaced fluorescent tubes in a much shorter timeframe IMHO- I work in a recently opened shop (3 years) that has already had it's nearly new fluorescent fittings removed and replaced with LED- and the quality of the lighting is actually better than the old ones. We still have some fluorescent lighting in the back-of-house areas, but these will no doubt be replaced by LEDs once the tubes fail. This seems to be the case in many of the shops in my city centre- switching to LED, despite the initial cost, really is a no-brainer.