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critical
1. Given to judging; especially given to adverse or unfavorable criticism; fault-finding, censorious.
2. Involving or exercising careful judgement or observation; nice, exact, accurate, precise, punctual.
3. Occupied with or skillful in criticism.
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Word Entries containing the term: “critical
rare-earth elements, REE, critical resources for high technology
The rare-earth elements (REE) form the largest chemically coherent group in the chemical periodic table.

Although they are generally unfamiliar, the rare-earth elements are essential for many hundreds of applications.

The versatility and specificity of the rare-earth elements have given them a level of technological, environmental, and economic importance considerably greater than might have been expected from their relative obscurity.

As technological applications of rare-earth elements have multiplied over the past several decades, demand for several of the less abundant (and formerly quite obscure) REE has increased dramatically.

Some of the Applications of the Rare-Earth Elements

  • Color cathode-ray tubes and liquid-crystal displays used in computer monitors and televisions employ europium as the red phosphor and no substitute is currently known.
  • Fiber-optic telecommunication cables provide much greater bandwidth than the copper wires and cables they have largely replaced.
  • Fiber-optic cables can transmit signals over long distances because they incorporate periodically spaced lengths of erbium-doped fiber that function as laser amplifiers because it alone possesses the required optical properties.
  • Permanent magnet technology has been revolutionized by alloys containing neodymium, samarium, gadolinium, dysprosium, or praseodymium.
  • Small, lightweight, high-strength rare-earth element magnets have allowed miniaturization of numerous electrical and electronic components used in appliances, audio and video equipment, computers, automobiles, communications systems, and military gear.
  • Several rare-earth elements are essential constituents of both petroleum fluid cracking catalysts and automotive pollution-control catalytic converters.
  • Although more expensive, lanthanum-nickel-hydride batteries offer greater energy density, better charge-discharge characteristics, and fewer environmental problems when they are recycled or disposed of.
  • The rare earth elements are essential for a diverse and expanding array of high-technology applications, which constitute an important part of the industrial economy of the United States.
  • Long-term shortages or unavailability of rare-earth elements would force significant changes in many technological aspects of American life.
  • State-run Chinese firms sharply expanded production and slashed prices of rare earths in the 1990's, forcing producers in the United States (previously the world’s leading producer and exporter) and elsewhere out of the market which no doubt will change now that China has restricted its exports of rare-earth minerals.
—Compiled primarily from information located at the
U.S. Geological Survey web site.
This entry is located in the following unit: rar-, rare- + (page 1)