Aluminum oxide corundum

W. A. Roth, U. Wolf, and O. Fritz, The Heat of Formation of Aluminum Oxide (Corundum) and of Lanthanum Oxide, Zeit. Elektro. u. Angew. Physik. Chemie, 46,42 (1940). 

The first laser produced was the ruby laser, invented in 1960. Rubies are crystals of aluminum oxide (corundum, AI2O3), containing about 0.5% chromium ions Cr3+, as substitution impurities, CrA, and laser action, as well as color, is entirely due to these... 

The absorption due to relaxation between the possible directions of the Jahn-Teller distortions was observed initially in experiments done on the crystals of aluminum oxide (corundum), yttrium aluminum garnet, yttrium iron garnet, and lithium gallium spinel doped with 2>d ions [10,11]. 

Now we will overview some experiments that reveal the specificities of the Jahn-Teller effect in diluted crystals. First of all, we will discuss a justification of their relaxation origin. We have mentioned before that the first experiments were done on the crystals of aluminum oxide (corundum), yttrium aluminum garnet, yttrium iron garnet, and lithium gallium spinel doped with a number of 3d ions [10,11]. The main result was the discovery of attenuation maximum which was considered to be observed at cot 1 and reconstruction of the relaxation time temperature dependence. In some experiments reported later both the velocity and attenuation of ultrasound were measured as functions of the temperature. They were done on ZnSe and ZnTe crystals doped with transition metals. These crystals have the zinc-blende structure with the Jahn-Teller ion in tetrahedral coordination. The following... 

As the temperature of a material is increased it is generally found that Young s modulus slowly decreases as shown for single-crystal aluminum oxide (corundum) in... 

Most important mineral Aluminum oxide, corundum AI Oj (Figure M49) is used as an abrasive. 

Figure 2.21. Schematic of the a-Al203 (aluminum oxide, corundum) crystal structure. Shown is the hep array of ions with ions and vacancies in the octahedral c-sites above the A plane of the oxide ions. The comparative stacking sequences of AI2O3 and FeTi03 (ihnenite) are also illustrated.

AI2O3 -1574.9 Anhydrous aluminum oxide (corundum), a-Al203... 

The abrasives used for coatings are diamond, aluminum oxide (corundum), silicon carbide, boron carbide, boron nitride, emery, flint (quartz), and garnet. These range in hardness and cost. Typically the superabrasives, synthetic diamond and cubic boron nitride, do not compete easily with the standard abrasives. 

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