Tetragonal crystal

Calcium Molybdate, CaMo04, occurs Yvith the tungstate in the mineral powellite (see p. 111). The normal salt is formed as a white precipitate when calcium chloride is added to a hot concentrated solution of sodium molybdate. - It may also be obtained, in a manner similar to that used for the barium salt, as white microscopic crystals, tetragonal bipyramidal, with a c==l 1-5457. 

Let s consider as an example the elementary excitations of the TmV04 crystal in the external magnetic field H parallel to the crystal tetragonal (at T > Tc) c-axis. 

K. Park and D.R. Olander, Oxygen diffusion in single-crystal tetragonal zirconia. /. Electrochem. Soc., 138(4) (1991) 1154-1159. 

We can conclude that the pattern of any two-parameter crystal (tetragonal, hexagonal, or rhombohedral) can be indexed on the appropriate Hull-Davey or Bunn chart. If the structure is known, the procedure is quite straightforward. The best method is to calculate the cja ratio from the known parameters, lay a straightedge on the chart to discover the proper line sequence for this value of c/a, calculate the value of sin 6 for each line from the indices found on the chart, and then determine the indices of the observed lines by a comparison of calculated and observed sin 6 values. 

Dark green octahedral crystals (tetragonal symmetry). Oxidizes in air and dec on contact with water. Should be stored in sealed ampuls, df 4.725. mp 590", bp 791. Heat of formation (solid) 250.9 kca] / mo] at 0. Fteely sol in water (dec). Also so] in polar organic solvents. Insol in nonpolar solvents such as hydrocarbons and ethyl ether. 

Ridruejo, A., Pastor, J. Y, Llorca, J., Sayir, A., Orera, V. M. (2005). Stress corrosion cracking of single-crystal tetragonal Zr02(Er203). Journal of the American Ceramic Society, SS(ll), 3125-3130. doi 10.1111/j.l551-2916.2005.00573.x. 

Moreover, our recent studies indicate that mono-dispersed and well-crystallized tetragonal zirconia nano-powders can be easily obtained by low temperature oxidation of a vacancy ordered ZrC (Hu et al., unpublished). It may be a new routine to prepare the metastable zirconia nano-powder. Thus, it is important to figure out what happen in the oxidation process of ZrC as well as to prevent or take advantage of it. 

Fig. 3. Crystal structure and lattice distortion of the BaTiO unit ceU showiag the direction of spontaneous polarization, and resultant dielectric constant S vs temperature. The subscripts a and c relate to orientations parallel and perpendicular to the tetragonal axis, respectively. The Curie poiat, T, is also shown.

Properties. Other names for potassium bifluoride are potassium hydrogen difluoride and potassium acid fluoride. This white crystalline salt is a soft, waxy soHd. The crystal forms of potassium bifluoride are tetragonal and cubic (21). The bifluoride ion in KHF2 averages 0.2292 nm between fluoride... 

In general, the chemistry of inorganic lead compounds is similar to that of the alkaline-earth elements. Thus the carbonate, nitrate, and sulfate of lead are isomorphous with the corresponding compounds of calcium, barium, and strontium. In addition, many inorganic lead compounds possess two or more crystalline forms having different properties. For example, the oxides and the sulfide of bivalent lead are frequendy colored as a result of their state of crystallisation. Pure, tetragonal a-PbO is red pure, orthorhombic P PbO is yeUow and crystals of lead sulfide, PbS, have a black, metallic luster. 

P-manganese(IV) oxide [14854-26-3] Mn02 black to gray crystal sohd tetragonal D14 Ah 5.026 535 insol H2O... 

Mercuric Cyanides. Mercuric cyanide7, Hg(CN)2, is a white tetragonal crystalline compound, Httle used except to a small degree as an antiseptic. It is prepared by reaction of an aqueous slurry of yellow mercuric oxide (the red is less reactive) with excess hydrogen cyanide. The mixture is heated to 95°C, filtered, crystallized, isolated, and dried. Its solubihty in water is 10% at 25°C. 

Polymorphism. Many crystalline polyolefins, particularly polymers of a-olefins with linear alkyl groups, can exist in several polymorphic modifications. The type of polymorph depends on crystallisa tion conditions. Isotactic PB can exist in five crystal forms form I (twinned hexagonal), form II (tetragonal), form III (orthorhombic), form P (untwinned hexagonal), and form IP (37—39). The crystal stmctures and thermal parameters of the first three forms are given in Table 3. Form II is formed when a PB resin crystallises from the melt. Over time, it is spontaneously transformed into the thermodynamically stable form I at room temperature, the transition takes about one week to complete. Forms P, IP, and III of PB are rare they can be formed when the polymer crystallises from solution at low temperature or under pressure (38). Syndiotactic PB exists in two crystalline forms, I and II (35). Form I comes into shape during crystallisation from the melt (very slow process) and form II is produced by stretching form-1 crystalline specimens (35). 

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