Using RGB LED combinations, the limit presently is the poor efficacy of available Green LEDs, compared to Blue and Red.
Presently, a Blue LED with Green/Yellow phosphor creates more visible light than a direct Green/Yellow LED.
This is an active area of research, and there are reports of promising advances.
Using RGB mixing to produce 'white' light gives a lower CRI (colour rendering index) than white LEDs using a broad-spectrum phosphor. For example, your eye sees Green+Red as yellow, but neither of them may reflect much from a Yellow banana, making it look brown!
Yet observers generally consider RGB illumination to give more attractive looking colours. For this reason, a new CQS (colour quality system) measure is being developed.
Does it surprise anyone, that once the Chinese have acquired a supply monopoly (under-cutting prices, so other rare-earth suppliers shut down), they now capitalise on it to boost their domestic phosphor, LED and fluorescent manufacturing industry?!
It has been obvious to me for years that China's long-term plan was to become the world's manufacturer by price cutting, than later milk that dependence for profit and influence. Now no-one can afford to anger China.
Exactly! My bet is, the bean counters determined that importing from China was cheaper than producing our own. As always, you attempt to maximize profit.
No surprise that this gives China leverage. It's up to us to create the opposing force. As always in business.
No sense whining about what we do to ourselves.
This is no new news. China has been flexing its rare-earth bully card for years. What is a greater concern is why the US was so willing to sell out its domestic production for a song, and then complain that China was hording.
When it comes to phosphors needed in lighting, I may suggest that a better way to create white light, at least for LEDs, is to mix the three primary colors. You get a more useful white light, more easily adjustable, could even be made user adjustable, and no need for any phosphors.
Of course, it goes without saying, any reliance on an individual country for a needed raw material will lead to artificial price hikes and shortages. It's entirely up to the rest of us to mitigate the problem, I think.
Back in 1886, Hyacinth Secretan and the Copper Syndicate tried to corner the market on copper, all the rage at the dawn of electricity. In the end, all he did was encourage switching to other materials, and make the reclaimation of copper profitable -- at which point the market collapsed and his syndicate was sitting on more copper than it could pay for. I suspect that the same is in the offing for the Peoples Republic of China. Ironic if it leads to the revolution that finally overthrows the provably defunct centrally planned economy.
The irony about rare earths is that they are not really that rare (n the Earth's crust)), but rather that there are just not very many mines open. As more mines do open (outside China) the problem will also be mitigated by alternative materials, like the nitirdes mentions here, which can be synthesized in the lab without the need for any mining at all. In the short term, however, China will probably convince many manufacturers to move operations there.
A Book For All Reasons Bernard Cole1 Comment Robert Oshana's recent book "Software Engineering for Embedded Systems (Newnes/Elsevier)," written and edited with Mark Kraeling, is a 'book for all reasons.' At almost 1,200 pages, it ...