the LANTHANIDES and the electromagnetic
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applications. Newer ones include material-source coding and remote thermometry through glass fibers.
Cerium in glass prevents browning — either from electron bombardment, as in the faceplate of your TV tube, or from gamma-rays, as in nuclear shielding windows. The secret is in cerium's dual valence ( C e 3 + ^ Ce4+ + e) which prevents color-center formation by control of free electrons.
ELECTRO-OPTICS & ELECTROCHROMISM Certain lanthanide polycrystalline ceramics and metallo-organics can store images on electrical cue or change color with voltage. The L in the electro-optical PLZT is for 4% lanthanum; thin films of lanthanide phthalocyanines promise flat multicolor displays of voltage-controlled pixels.
IMAGE INTENSIFICATION X-ray intensification screens rely on efficient conversion of the x-radiation into longer film-sensitive wavelengths. Diagnostic x-ray doses are being drastically reduced by replacing Edison's classic calcium tungstate screen phosphors with more efficient lanthanum and gadolinium salts.
LASERS The favorite laser wavelength is 1.06 microns in the infrared (or 0.53 microns in the visible green after frequency-doubling). Why? 1.06 microns is the emission from a neodymium ion as it drops from its excited state to its natural energy level. Nd-in-glass lasers are classic; Nd:YAG is the standard solid state laser for surgery and dozens of other uses; NdP5014 is the newest minilaser crystal.
UV ABSORPTION Ultraviolet radiation can alter foods, oils, dyes, biologicals and such. Cerium in glass containers, street light envelopes and gallery windows will absorb UV without altering transmission in the visible. Biochemists, packers and museums capitalize upon this property.
INFRARED WINDOWS
TRANSMISSION SPECTRA
Both a glassy CaLa2S4 structure and various lanthanides in vitreous fluoride compositions make more durable windows for passing radiation of 8 to 12 micron wavelength, in infrared detection and imaging. Their uses range from medical diagnosis, to geological surveys from space, to defense ordnance.
Nd, Pr, Er and Ho have strong, unique absorption bands in the visible spectrum — and are therefore incorporated in photographic filters, welder's goggles and optical instrument windows. Nd is especially useful in glass for attenuating the ubiquitous yellow sodium lines.
MICROWAVE CONTROL
PHOSPHORS
Lanthanide polycrystalline materials regulate microwave transmission. Ferrimagnetic YIG's and GIG's (yttrium-iron and gadolinium-iron garnets, sometimes with aluminum also in the structure) are fabricated into microwave circulators, gyromagnetic resonators, scanners and phase shifters — for directing and manipulating signals and energy in radar, ovens, telecommunications, and intercept networks. ^*
Lanthanide ions, on excitation, luminesce in colorful variety. Eu(lll), Eu(ll), Tb, Er, Tm, Nd, Dy, Ce, Sm, Yb & Ho ions in suitable crystal lattices form useful phosphors. The red of TV and certain prime colors in fluorescent lighting represent major THE LANTHANIDE MINERAL is bastnasite, 12% of the ore we mine at Mtn. Pass, California (supplying over half of free world need). It contains all nine of the principal lanthanides, in proportions much as in the exploding pie chart at the left. Forty million tons of ore are in the deposit — ample for decades to come. CIRCLE 19
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THE LOOK OF TOMORROW through LANTHANIDE CHEMISTRY
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