Zirconium oxide cubic form

Similarly, fusion of milled zircon with dolomite or lime forms CaSiO and MgZrO [12032-31 -4] CaZrO [12013-47-7] and CaO Ca2SiO or CaSiO and Zr02, and is used to prepare zirconium oxide, usually as calcia-stabiUzed cubic zirconia because of the calcia left in soHd solution in the zirconia (27-29). 

Stabilized zirconia refers to a solid solution of zirconium oxide with one or more of a number of stabilizing oxides (CaO, MgO, 20, or others) to form a cubic fluorite structure. This... 

Zirconium oxide, or zirconia, occurs as the mineral baddeleyite, but zirconium oxide is obtained commercially mainly via its recovery from zircon. Zircon is treated with molten sodium hydroxide to dissolve the silica. Zirconia is used as a ceramic, but it must be doped with about 10 percent CaO or Y2O3 to stabilize it in its face-centered cubic form. Zirconia is monoclinic, meaning that it has one oblique intersection of crystallographic axes, but it undergoes a phase change at about 1,100°C (2,012°F), its crystal structure becoming tetragonal, and above 2,300°C (4,172°F) it becomes cubic. To... 

All the samples had a polycrystalline structure. Nevertheless, it has been established that the appearance of the isolated clusters of defects is observed in the FSZ structure at the initial stage of irradiation with high-energy xenon and iodine ions. In the sequel, the density of defects increases. However, at a relatively low dose of 3 dpa, the saturation stage is formed, and after its formation the material structure remains unchanged. The exposure of monoclinic zirconium oxide to the radiation dose of 2 dpa results in the transformation of monocUnic structme into more densely packed cubic and tetragonal structmes. During further increase in the radiation dose up to 680 dpa, amorphization is not observed. 

Zirconium dioxide (Zr02), commonly called zirconium oxide, forms three phases, with a monoclinic, a tetragonal, and a cubic crystal structure. Dense parts may be obtained by sintering of the cubic or tetragonal phase only. In order to stabilize the cubic phase, stabilizers such as MgO, CaO, Y2O3, and Ce02 are added. 

As compared to unalloyed zirconium, zircaloy-2 has an improved character in oxide formation at elevated temperatures. A tightly adherent oxide film forms on this alloy at a rate that is at first quasi-cubic, but after an initial period undergoes a transition to linear behavior. Unlike the white, porous oxide films, on unalloyed zirconium, the oxide film on zircaloy-2 remains dark and adherent throughout transition and in the posttransition region. 

In the range in which zirconium shows corrosion resistance in H2SO4, a passive film is formed on zirconium that is predominantly cubic zirconium oxide (Zr02) with only traces of the monoclinic phase. ° Zirconium corrodes in highly concentrated H2SO4 (e.g., 80%) because loose films are formed that prove to be zirconium disulfate tetrahydrate [Zr(S04)2-4H20]. Also, at the higher acid concentrations, films that flake off are formed and are probably partly zirconium hydrides. ... 

Arkelite is a naturally occurring cubic form of zirconium oxide, although it is a rare mineral. The material was first discovered by the German chemist Klaproth in 1789 from the reaction of zircon compounds with alkalis. The natural form is closely related to baddeleyite (q.v.) and is listed with variable oxygen contents (for example, ZrOj 7 and Zr02.i2). It may occur as a minor component in many different rock types. 

Lead zirconate [12060-01 -4] PbZrO, mol wt 346.41, has two colorless crystal stmctures a cubic perovskite form above 230°C (Curie point) and a pseudotetragonal or orthorhombic form below 230°C. It is insoluble in water and aqueous alkaUes, but soluble in strong mineral acids. Lead zirconate is usually prepared by heating together the oxides of lead and zirconium in the proper proportion. It readily forms soHd solutions with other compounds with the ABO stmcture, such as barium zirconate or lead titanate. Mixed lead titanate-zirconates have particularly high piezoelectric properties. They are used in high power acoustic-radiating transducers, hydrophones, and specialty instmments (146). 

Ceria-zirconia nanophases were synthesied by a surfactant-assisted method. The refined structural data concerning the crystallite size, lattice parameters, structural microstrain, cationic occupy number and cationic defect concentration are reported. Zirconium addition into the cubic structure of ceria inhibits crystal sintering but leads to structure distortion. Different CO-metal bonds are formed when CO chemisorbs on Pd-loaded CesZr. x02 catalysts. Catalytic tests reveal that the lower zirconium content benefits the CO oxidation. 

Catalysts active in the isomerization of n-butane have been synthesized by depositing sulfate ions on well-crystallized defective cubic structures based on ZrOz. This technique for introduction of sulfates does not result in any significant changes in the bulk properties of zirconium dioxide matrix. Active sulfated catalysts were prepared on the basis of cubic solid solutions of ZrOz with calcium oxide and on the basis of cubic anion-doped ZrOz. The dependence of the catalytic activity on the amount of calcium appeared to have a maximum corresponding to 10 mol.% Ca. Radical cations formed after adsorption of chlorobenzene on activated catalysts have been used as spin probes for detection of strong acceptor sites on the surface of the catalysts and estimation of their concentration. A good correlation has been observed between the presence of such sites on a catalyst surface and its activity in isomerization of n-butane. 

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