Better fluorescent lighting through physics

New kinds of fluorescent lighting phosphors have been developed that reportedly use far fewer rare-earth elements than current technology.

A collaboration between General Electric (GE), Lawrence Livermore National Laboratory (LLNL) and Oak Ridge National Laboratory, funded by the Department of Energy’s Office of Energy Efficiency and Renewable Energy, have made discoveries that should help to reduce the reliance on fluorescents which use a high amount of rare-earth elements.

Rare-earth elements are scarce in the United States and the country mainly relies on imports. Phosphors in current fluorescent lighting technology consume more than 1000 metric tons of rare-earth oxides yearly, including europium (Eu), terbium (Tb), cerium (Ce) and lanthanum (La), as well as even larger amounts of yttrium (Y) oxide.

While it is expected that LED lighting will likely replace fluorescent tubes at some point in the future, low-cost linear fluorescent lighting is anticipated to remain a dominant lighting option for some time to come.

The researchers, who also worked with the Critical Materials Institute (CMI), looked into replacing the current triphosphor blend (based on a mixture of blue, green and red emitters), which was discovered more than 30 years ago, because of its high rare-earth consumption.

“The fundamental physics of these phosphors is compelling, and we are taking the next steps to assess their feasibility for commercial lighting by evaluating chemical issues such as slurry compatibility and improving the synthetic procedures,” said Steve Payne, the CMI thrust leader on the project.

The collaborators identified a green phosphor, which reduces the Tb content by 90% and eliminates La, while the new red phosphor eliminates both Eu and Y and is rare-earth free.

These proposed phosphors appear to be close to meeting stringent requirements of long lamp survivability, high efficiency, precise colour rendition and low cost, while the blue phosphor has inherently low rare-earth content and need not be replaced.

Image caption: At left, Nerine Cherepy of LLNL displays commercial phosphors (six samples from bottom left of semicircle) and phosphors being developed by LLNL and collaborators as replacements (five on right). LLNL, Oak Ridge National Laboratory and GE are working to improve the efficiency of the new phosphors to replace commercial phosphors. Inset: The CMI phosphor team members include (from left) Paul Martinez, Cherepy, Zach Seeley, Kiel Holliday, Ich Tran, Nick Harvey and Steve Payne. Not shown are Daniel Aberg and Fei Zhou. Images courtesy of LLNL.

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