A few weeks ago I wrote that one of the most important changes that has taken place in the rare earths field is in the lighting market. Fluorescent tubes work by bouncing electrons on atoms of a refined gas in a glass tube and exciting the atoms, which then emit UV photons. These photons hit fluorescent molecules that convert the high-energy UV light into visible light.
For those of you who did not know: sitting under a naked fluorescent light, compact or not, means having great confidence in the manufacturer's quality control. Because only when the phosphor coating is extremely uniform and complete, no bad UV light escapes, which can cause skin cancer. Keep the fluorescent lamps behind plastic or glass to make sure that does not happen.
For the production of fluorescent light, a glass tube is needed, as well as a liquid phosphor particle suspension, so as to coat the inside of the tube. Once the liquid has evaporated, the glass tube is heated to the point where the glass softens and the phosphor particles adhere to the tube. Then the tube is filled with gas and sealed.
Today, rare earths such as yttrium and cerium are used as carriers and terbium and europium as dopants and light emitters for the best phosphors. Someone realized a while ago that while the phosphor particles are smaller than 10 μm, only the surface and the area directly below it interact with the UV photons.
As rare earths became more expensive and harder to obtain, several companies decided to produce phosphor particles by producing free carrier particles without rare earths and coating the carrier particles with phosphor material. The result in terms of lighting was the same. The costs were, due to the lower use of high-priced rare earths, equal to lower.
The general view is that we are in the transition from fluorescent tubes to LEDs. One reader asked how these changes would affect the demand for rare earths. While LEDs contain less phosphor material, the demand for rare earths could increase as many more LEDs are required.
I think it's easy to answer the question about the number of material requirements needed per unit. A typical LED has a luminous efficacy above 110 lm / W and the devices typically have 1 W power and contain an approximately 1 mm2 gallium nitride chip with a phosphor coating of about 4 mg / mm2 (a Nichia patent). The same specifications for a T8 fluorescent tube say that the light output is about 90 lm / W, but the power consumption in an 900mm tube is about 30 W, with an inside area of 456 cm2 (according to a GE patent) and about 2,5 mg / cm2 phosphor coatings. This tells us that a single 8 mm tube of T900 length X produces approximately 2700 lumens of light and contains approximately 1.140 mg of phosphorus. In order to produce the same 2.700 lumens of light, possibly even of better quality, 25 LEDs with a total of 100 mg phosphorus are necessary.
It appears that the phosphors used contain almost exactly the same amounts of rare earths, since the mechanisms for producing the visible light are basically the same for an LED and a fluorescent lamp.
The required amount of phosphorus and thus of rare earths per generated amount of light is decidedly lower for LEDs than for phosphors. Note that we are not discussing power consumption in lighting here. The LED lights consume less power, but they require significantly less rare earths to do so.
All of the above numbers were generated before the recent development of phosphor-coated carrier particles. The amount of phosphorus for efficient lighting has now dropped dramatically and will continue to fall as LEDs, phosphors and bulbs replace.
But there is hope. According to GE in the year 2013, LED lights currently make up only 18% of the market and incandescent bulbs are still an important player. However, GE also says that LEDs' market share is expected to increase by 70% in 2020, especially at the expense of incandescent.
Most of this increase comes from laws in the US, as well as restrictions in China, which require reduced energy consumption for lighting in government and office buildings. Aside from additional technology developments aimed at reducing phosphorus, the shift to LED lighting may provide some kind of rejoicing to rare earth suppliers.
Source: http://investorintel.com/rare-earth-intel/lighting-way-rare-earths-lighting/
