Lead oxide tetragonal

The measures of solid state reactivity to be described include experiments on solid-gas, solid-liquid, and solid-solid chemical reaction, solid-solid structural transitions, and hot pressing-sintering in the solid state. These conditions are achieved in catalytic activity measurements of rutile and zinc oxide, in studies of the dissolution of silicon nitride and rutile, the reaction of lead oxide and zirconia to form lead zirconate, the monoclinic to tetragonal transformation in zirconia, the theta-to-alpha transformation in alumina, and the hot pressing of aluminum nitride and aluminum oxide. 

The red lead oxide (the tetragonal alpha modification) is obtained by slow cooling of the lead monoxide melt. The sohdified mass may contain the red alpha form of the oxide resulting from slow cooling of the melt, under an outer layer of yellow beta form that may result from the rapid cooling of the outer portion. 

Meyer B, Ziemer B, Scholz F (1995) In Situ X-ray diffraction study of the electrochemical reduction of tetragonal lead oxide and orthorhombic Pb(OH)Cl mechanically immobilized on a graphite electrode. J Electroanal Chem 392 79-83. 

Addition of base to lead(II) solutions gives the hydrous oxide, which dissolves in an excess of base to give the plumbate ion. If aqueous ammonia is added to a lead acetate solution, a white precipitate of a basic acetate is formed. On suspension in warm aqueous ammonia and subsequent drying, it yields a very pure lead oxide, which is most stable in the tetragonal red form. 

This lead compound exists in two polymorphic forms tetragonal (P-PbO) and orthorhombic (a-PbO). The solubility of the two forms in water at 25 °C is 0.0504 g for a-PbO and 0.1065 g for 3-PbO [6]. Lead oxide forms lead hydroxides, 3Pb0-H20 and 5PbO H2O [7,8]. Lead oxide is hydrated forming Pb(OH)2, a compound of amphoteric nature. It dissociates to HPb02 and Pb(OH) ions. In the battery industry, lead oxide is obtained by partial thermal oxidation of lead and is ealled leady oxide , as it eontains between 73% and 85% PbO, the remaining part being non-oxidized lead. The basie eonstituent of leady oxide is tet-PbO, but orthorhombie PbO is also present, up to 5—6%. Leady oxide is used for tbe preparation of the pastes for lead—aeid battery plate production. 

Lead oxide (PbO) exists in two modifications (polymorphs) (1) red tetragonal lead oxide (tet-PbO) (also known as a-PbO or litharge) and (2) yellow orthorhombic lead oxide (orthorhomb-PbO) (also known as P-PbO or massicot). Tet-PbO is stable at low temperatures and low pressures. The transition temperature of tet-PbO to orthorhomb-PbO is 486—489 °C and the thermal effect of the transition is 1.35 kJ mol When orthorhomb-PbO is cooled rapidly, it may remain unchanged and continue to exist at low temperatures. Eventually, it is slowly transformed into tet-PbO under external physical action. Lead oxide exists also in amorphous form. The latter s amount depends on the method of manufacture of PbO. 

The crystal modification of the lead oxide depends on the conditions of its manufacture. At temperatures of oxidation below 470 °C (as is the case with ball mill PbO), the tetragonal polymorph is formed. If oxidation is performed in the temperature range of 460—470 °C through the Barton process, 60—70 wt% of the lead oxide formed is tetragonal (a-PbO), 15—20 wt% is orthorhombic (p-PbO) and the remaining balance is amorphous lead oxide. 

The polycrystalline film consists of the tetragonal phase of PZT with peaks arising at approximately 20 = 22 , 31°, 39°, 45°, and 55°. Tliese peaks correspond to the (100), (110), (111), (200), and (211) orientations, respectively. A bro peak centered around 26 = 30° was also evident. This may correspond to the metastable pyrochlore phase. The pyrochlore phase is lead deficient, such that Pb, labeled x, in Pbx(Zro.4gTio.s2)03, is less than one, consistent with the loss of lead oxide during the anneal at 650°C. Lead oxide is known to evaporate from films during the thermal annealing conditions described here (17,18). 

Minium (syn., red lead oxide) [Named after the river Minius located in northwest of Spain] (ICSD 22325 and PDF 41-1494) Pb,PbO, M= 685.5976 90.67 wt.% Pb 9.33 wt.% 0 (Oxides and hydroxides) Tetragonal P.G. -4 Spinel type Uniaxial n-2.42 2.5-3 8200 Habit scaly, massive, granular, striated. Color light red, brownish red, vivid red, or yellowish red. Luster adamantine. Diaphaneity subtransparent to opaque. Streak yellowish orange. Cleavage (110) perfect, [010] perfect. Fracture raithy. Occurrence Oxidized portions oflead ore deposits. 

The solid residues of the combustion of Pb(C2H5)4 in air or in argon-oxygen mixtures in the presence of hydrocarbons are rhombic PbO, PbC03, and small amounts of Pb304 and Pb(N02)2 when the combustion is performed in air [41]. Tetragonal and rhombic lead oxide are products of the oxidation at temperatures between 250 and 560 °C [23], e.g., at410°C [44]. 

Lead oxide PbO (plumbous oxide) can exist in two different modifications. Red lead oxide PbO precipitates in tetragonal crystals. Yellow lead oxide precipitates in rhombic crystals. Yellow Iccid oxide is also called Litharge (= Stone Silver ) this is because this oxide precipitates as slags when plumbiferous silver is refined. According to Atkins Physical Chemistry, these modifications of lead oxide have the following thermodynamic standard values ... 

Structures modules of VMSE, located on the book s website [www.wiley.com/coUege/callister (Student Companion Site)], generate (and print out) a three-dimensional unit cell for lead oxide, PbO, given the following (1) The unit cell is tetragonal with a = 0.397 nm and c = 0.502 nm. 

Table A.20. X-Ray Powder File, Lead Oxide, PbO, Tetragonal...

Notes Identification lead oxide Unit cell composition Pb02 Crystalline structure tetragonal... 

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. 

Much confusion exists concerning the number, composition, and structure of the oxides of lead. PbO exists as a red tetragonal form (litharge) stable at room temperature and a yellow orthorhombic form (massicot) stable above 488°C. Litharge (mp 897°, d 9.355 gcm ) is not only the most important oxide of Pb, it is also the most widely used inorganic compound of Pb (see Panel on p. 386) it is made by reacting molten Pb with air or O2 above 600° and has the SnO structure (p. 383, Pb-O 230 pm). Massicot (d 9.642 gcm ) has... 

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