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Gadolinium Gallium Garnet
Gadolinium Gallium Garnet (GGG, ) is a synthetic crystalline material of the garnet group, with good mechanical, thermal, and optical properties. It is typically colorless. It has a cubic lattice, a density of 7.08 g/cm3 and its Mohs hardness is variously noted as 6.5 and 7.5. Its crystals are produced with the Czochralski method. During production, various dopants can be added for colour modification. The material is also used in fabrication of various optical components and as a substrate material for magneto–optical films ( magnetic bubble memory).J. F. Greber "Gallium and Gallium Compounds" in Ullmann's Encyclopedia of Industrial Chemistry, 2012 Wiley-VCH, Weinheim. It also finds use in jewelry as a diamond simulant. GGG can also be used as a seed substrate for the growth of other garnets such as yttrium iron garnet. See also * Micro-pulling-down * Terbium gallium garnet * Yttrium aluminium garnet Yttrium aluminium garnet (YAG, Y3 Al5 O12) is a synthetic crystalline mat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gemological Institute Of America
The Gemological Institute of America (GIA) is a nonprofit institute based in Carlsbad, California. It is dedicated to research and education in the field of gemology and the jewelry arts. Founded in 1931, GIA's mission is to protect buyers and sellers of gemstones by setting and maintaining the standards used to evaluate gemstone quality. The institute does so through research, gem identification and diamond grading services and a variety of educational programs. Through its library and subject experts, GIA acts as a resource of gem and jewelry information for the trade, the public and media outlets. In 1953 the GIA developed its International Diamond Grading System and the "four Cs" (cut, clarity, color, and carat weight) as a standard to compare and evaluate the quality of diamonds. Today, the institute is headquartered in Carlsbad, California and operates in 13 countries, with 11 campuses, 9 laboratories and 4 research centers. History The story of the GIA begins in the 1 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Yttrium Iron Garnet
Yttrium iron garnet (YIG) is a kind of synthetic garnet, with chemical composition , or Y3Fe5O12. It is a ferrimagnetic material with a Curie temperature of 560 K. YIG may also be known as yttrium ferrite garnet, or as iron yttrium oxide or yttrium iron oxide, the latter two names usually associated with powdered forms. In YIG, the five iron(III) ions occupy two octahedral and three tetrahedral sites, with the yttrium(III) ions coordinated by eight oxygen ions in an irregular cube. The iron ions in the two coordination sites exhibit different spins, resulting in magnetic behavior. By substituting specific sites with rare-earth elements, for example, interesting magnetic properties can be obtained. YIG has a high Verdet constant which results in the Faraday effect, high Q factor in microwave frequencies, low absorption of infrared wavelengths down to 1200 nm, and very small linewidth in electron spin resonance. These properties make it useful for MOI ( magneto optical i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gallium Compounds
Gallium compounds compounds containing the element gallium. These compounds are found primarily in the +3 oxidation state. The +1 oxidation state is also found in some compounds, although it is less common than it is for gallium's heavier congeners indium and thallium. For example, the very stable GaCl2 contains both gallium(I) and gallium(III) and can be formulated as GaIGaIIICl4; in contrast, the monochloride is unstable above 0 °C, disproportionating into elemental gallium and gallium(III) chloride. Compounds containing Ga–Ga bonds are true gallium(II) compounds, such as GaS (which can be formulated as Ga24+(S2−)2) and the dioxan complex Ga2Cl4(C4H8O2)2.Greenwood and Earnshaw, p. 240 Aqueous chemistry Strong acids dissolve gallium, forming gallium(III) salts such as (gallium nitrate). Aqueous solutions of gallium(III) salts contain the hydrated gallium ion, . Gallium(III) hydroxide, , may be precipitated from gallium(III) solutions by adding ammonia. Dehydrating ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oxides
An oxide () is a chemical compound that contains at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion of oxygen, an O2– (molecular) ion. with oxygen in the oxidation state of −2. Most of the Earth's crust consists of oxides. Even materials considered pure elements often develop an oxide coating. For example, aluminium foil develops a thin skin of Al2O3 (called a passivation layer) that protects the foil from further corrosion.Greenwood, N. N.; & Earnshaw, A. (1997). Chemistry of the Elements (2nd Edn.), Oxford:Butterworth-Heinemann. . Stoichiometry (the measurable relationship between reactants and chemical equations of a equation or reaction) Oxides are extraordinarily diverse in terms of stoichiometries and in terms of the structures of each stoichiometry. Most elements form oxides of more than one stoichiometry. A well known example is carbon monoxide and carbon dioxide.Greenwood, N. N.; & Earnshaw, A. (1997). Chemistry ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Synthetic Minerals
Synthetic things are composed of multiple parts, often with the implication that they are artificial. In particular, 'synthetic' may refer to: Science * Synthetic chemical or compound, produced by the process of chemical synthesis * Organic compound#Synthetic compounds, Synthetic organic compounds synthetic chemical compounds based on carbon (organic compounds). * Synthetic peptide * Synthetic biology * Synthetic elements, chemical elements that are not naturally found on Earth and therefore have to be created in experiments Industry * Synthetic fuel * Synthetic oil * Synthetic marijuana * Synthetic diamond * Synthetic fibers, cloth or other material made from other substances than natural (animal, plant) materials Other * Synthetic position, a concept in finance * Synthetic-aperture radar, a type or radar * Analytic–synthetic distinction, in philosophy * Synthetic language in linguistics, inflected or agglutinative languages * Synthetic intelligence a term emphasizing that tr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Yttrium Aluminium Garnet
Yttrium aluminium garnet (YAG, Y3 Al5 O12) is a synthetic crystalline material of the garnet group. It is a cubic yttrium aluminium oxide phase, with other examples being YAlO3 (YAP) in a hexagonal or an orthorhombic, perovskite-like form, and the monoclinic Y4Al2O9 (YAM). Due to its broad optical transparency, low internal stress, high hardness, chemical and heat resistance, YAG is used for a variety of optics. Its lack of birefringence (unlike sapphire) makes it an interesting material for high-energy/high-power laser systems. Laser damage levels of YAG ranged from 1.1 to 2.2 kJ/cm² (1064 nm, 10 ns). YAG, like garnet and sapphire, has no uses as a laser medium when pure. However, after being doped with an appropriate ion, YAG is commonly used as a host material in various solid-state lasers. Rare earth elements such as neodymium and erbium can be doped into YAG as active laser ions, yielding Nd:YAG and Er:YAG lasers, respectively. Cerium-doped YAG (Ce:YAG ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Terbium Gallium Garnet
Terbium gallium garnet (TGG) is a kind of synthetic garnet, with the chemical composition . This is a Faraday rotator material with excellent transparency properties and is very resistant to laser damage. TGG can be used in optical isolators for laser systems, in optical circulators for fiber optic systems, in optical modulators, and in current and magnetic field sensors. TGG has a high Verdet constant which results in the Faraday effect. The Verdet constant increases substantially as the mineral approaches cryogenic temperatures. The highest Verdet constants are found in terbium doped dense flint glasses or in crystals of TGG. The Faraday effect is chromatic (i.e. it depends on wavelength) and therefore the Verdet constant is quite a strong function of wavelength. At 632 nm, the Verdet constant for TGG is reported to be , whereas at 1064 nm it falls to . This behavior means that the devices manufactured with a certain degree of rotation at one wavelength, will produce m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Micro-pulling-down
The micro-pulling-down (μ-PD) method is a crystal growth technique based on continuous transport of the melted substance through micro-channel(s) made in a crucible bottom. Continuous solidification of the melt is progressed on a liquid/solid interface positioned under the crucible. In a steady state, both the melt and the crystal are pulled-down with a constant (but generally different) velocity. Many different types of crystal are grown by this technique, including Y3Al5O12, Si, Si-Ge, LiNbO3, α-Al2O3, Y2O3, Sc2O3, LiF, CaF2, BaF2, etc. Crystal growth routine Standard routine procedure used in the growth of most of μ-PD crystals is well developed. The general stages of the growths include: * Charging of the crucible with starting materials (mixture of powders) * Heating of the crucible until starting materials in the crucible are completely melted * Upward displacement of the seed until its contact with the meniscus or crucible * Formation of the meniscus and p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diamond Simulant
A diamond simulant, diamond imitation or imitation diamond is an object or material with gemological characteristics similar to those of a diamond. Simulants are distinct from synthetic diamonds, which are actual diamonds exhibiting the same material properties as natural diamonds. Enhanced diamonds are also excluded from this definition. A diamond simulant may be artificial, natural, or in some cases a combination thereof. While their material properties depart markedly from those of diamond, simulants have certain desired characteristics—such as dispersion and hardness—which lend themselves to imitation. Trained gemologists with appropriate equipment are able to distinguish natural and synthetic diamonds from all diamond simulants, primarily by visual inspection. The most common diamond simulants are high- leaded glass (i.e., rhinestones) and cubic zirconia (CZ), both artificial materials. A number of other artificial materials, such as strontium titanate and synthetic rut ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crystal
A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macroscopic single crystals are usually identifiable by their geometrical shape, consisting of flat faces with specific, characteristic orientations. The scientific study of crystals and crystal formation is known as crystallography. The process of crystal formation via mechanisms of crystal growth is called crystallization or solidification. The word ''crystal'' derives from the Ancient Greek word (), meaning both "ice" and "rock crystal", from (), "icy cold, frost". Examples of large crystals include snowflakes, diamonds, and table salt. Most inorganic solids are not crystals but polycrystals, i.e. many microscopic crystals fused together into a single solid. Polycrystals include most metals, rocks, ceramics, and ice. A third category of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Jewelry
Jewellery ( UK) or jewelry (U.S.) consists of decorative items worn for personal adornment, such as brooches, rings, necklaces, earrings, pendants, bracelets, and cufflinks. Jewellery may be attached to the body or the clothes. From a western perspective, the term is restricted to durable ornaments, excluding flowers for example. For many centuries metal such as gold often combined with gemstones, has been the normal material for jewellery, but other materials such as glass, shells and other plant materials may be used. Jewellery is one of the oldest types of archaeological artefact – with 100,000-year-old beads made from ''Nassarius'' shells thought to be the oldest known jewellery.Study reveals 'oldest jewellery' , '' |
Magnetic Bubble Memory
Bubble memory is a type of non-volatile computer memory that uses a thin film of a magnetic material to hold small magnetized areas, known as ''bubbles'' or ''domains'', each storing one bit of data. The material is arranged to form a series of parallel tracks that the bubbles can move along under the action of an external magnetic field. The bubbles are read by moving them to the edge of the material, where they can be read by a conventional magnetic pickup, and then rewritten on the far edge to keep the memory cycling through the material. In operation, bubble memories are similar to delay-line memory systems. Bubble memory started out as a promising technology in the 1970s, offering memory density of an order similar to hard drives, but performance more comparable to core memory, while lacking any moving parts. This led many to consider it a contender for a "universal memory" that could be used for all storage needs. The introduction of dramatically faster semiconductor memo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
