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 An innovative high-performance material: biofibers made from green lacewing silk
20.01.2017 | Fraunhofer-Institut für Angewandte Polymerforschung IAP

nachricht Treated carbon pulls radioactive elements from water
20.01.2017 | Rice University

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

Helmholtz International Fellow Award for Sarah Amalia Teichmann

20.01.2017 | Awards Funding

An innovative high-performance material: biofibers made from green lacewing silk

20.01.2017 | Materials Sciences

Ion treatments for cardiac arrhythmia — Non-invasive alternative to catheter-based surgery

20.01.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>