Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Blue Garnets

26.03.2004


Russian researchers produce crystals of various colors and shades based on yttrium, aluminium and oxygen. Outwardly, they practically do not differ from well-known semiprecious garnet stones. However, artificially produced crystals possess higher solidity, and the color variety is much wider than that of their natural “relatives”.



Sometimes a minor thing is sufficient to change the situation beyond recognition. That is particularly important in chemistry, especially in chemistry of crystals. A crystal is like a huge building constructed from atom “bricks”: in case of one redundant atom or vice versa – and the building changes the shape, the quality of such structure decreasing. To color the crystal building, small amounts (hundredth parts) of certain metals (color promoters) are required. Such admixtures of chromium and iron make the first-class gems – rubies and sapphires – from aluminium oxide.

Nature spends several years to achieve the result, however the laboratories need one or two days to produce the same. Laboratories also grow natural garnets, but the quality has to be sacrificed to the speed. Crystals of a large size (in this case, they are convenient for the jeweller’s art) can be grown up from the melt containing silicon o?ide, aluminium oxide, ferric oxide. Yttrium-aluminium garnets without admixtures are colorless. By adding different rare-earth metals in the course of preparing these crystals, not only the desired color can be ensured to clystals, but also the required shade. The advantage of these crystals is also that the color promoters are better distributed in them, therefore, producing the crystals of uniform color and high degree of purity.


To receive the yttrium-aluminium crystal with the structure of garnet, aluminium oxide and yttrium oxide were melted down at the 3:5 proportion. The obtained mixture was ground through to formation of the 5 millimeter granules. Then the calcined powders of rare-earth metals and zirconium, hafnium or titanium were mixed with granules of the yttrium-aluminium crystal, and the mixture was placed evenly in the boat container along its length. Then the boat container was placed in the gas-vacuum chamber. The mixture melted under the heater installed in the chamber, as the boat container moved away from the heater to a cooler area, crystallization was taking place. The so-called inoculum - nucleus of crystal - is preliminarily allocated for programming the direction of crystal growth, the inoculum possessing the miniparameters of the future macrocrystal.

Thus the researchers produced analogues to natural garnets of red and green colors, as well as pale blue garnets which do not exist in the natural environment. The red coloring of yttrium-aluminium garnets is caused by inclusion of zirconium ions in the crystal structure. Increasing the amount of zirconium may intensify the color. However, the researchers failed to get the desired variety of red shades. Introduction of scandium oxide in the melt solves the problem –the deepness and evenness of the color is increased. This is how garnets of bright red through crimson color were produced. The researchers can ensure various shades of violet color, to this end, part of yttrium ions should be additionally replaced by the europium ions – and garnets of multiple violet shades will be available to jewellers.

To produce the crystals imitating all natural garnets of green shades, yttrium-aluminium garnets are used with adding of ytterbium, zirconium and cerium. Increasing the amount of cerium ions in the crystal, the color may be changed from dark-green via bright green through yellow-green. Thus, can be achieved grass green, swamp green and emerald shades. If the researchers introduce in the crystal content the metal ions, the size of which are larger than that of the yttrium ions, then the blue-green crystal will be produced to imitate emerald stones.

The color of blue garnets which do not exist in the natural environment are caused by presence of the europium, zirconium and terbium ions in the structure of yttrium-aluminium garnets. It is possible now to produce sky-blue garnet (which is outwardly very similar to aquamarine) or garnets of violet-blue color and even of bright blue color with green shade.

Transparency, high solidity, large size – all these properties make the artificially produced garnets serious rivals to natural stones in the jeweller’s art. Natural stones yield in this connection to artificial jnes and cost much more than artificial stones. The produced crystals turned out to be excellent cutting material and fit for making elegant jewelry. The main consumers of artificial crystals are major associations and jewellery enterprises in Russia and foreign countries.

Sergey Komarov | alfa
Further information:
http://www.informnauka.ru

More articles from Materials Sciences:

nachricht Decoding cement's shape promises greener concrete
08.12.2016 | Rice University

nachricht Scientists track chemical and structural evolution of catalytic nanoparticles in 3-D
08.12.2016 | DOE/Brookhaven National Laboratory

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

Scientists track chemical and structural evolution of catalytic nanoparticles in 3-D

08.12.2016 | Materials Sciences

Decoding cement's shape promises greener concrete

08.12.2016 | Materials Sciences

Will Earth still exist 5 billion years from now?

08.12.2016 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>