Barium zirconate

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). 

Heat aging characteristics may be improved by the addition of a few per cent of ferric oxide and barium zirconate to name but two materials mentioned in the literature. 

Babilo, P. and Haile, S. M. Enhanced Sintering of Yttrium-Doped Barium Zirconate by Addition of ZnO, Journal of the American Ceram. Soc., 88, 2362 (2005). 

Brown JR, Mastromatteo E, Horwood J. 1963. Zirconium lactate and barium zirconate. Am Ind Hyg Assoc J 34 131-136. 

SYNS BARIUM ZIRCONATE BARIUM ZIRCONIUM OXIDE BARIUM ZIRCONIUM TRIOXIDE ZIRCONATE, BARIUM (1 1)... 

The development of electrolytes that exhibit a higher conductivity at low temperature. Three candidates have emerged, namely doped ceria, doped lanthanum gallate, and doped barium zirconate. The first two of these are oxygen ion electrolytes, and the latter is a proton conductor. 

Iwahara, H., Yajima, T, Hibino, T, Ozaki, K. and Suzuki, H. (1993) Protonic conduction in calcium, strontium and barium zirconates. Solid State Ionics, 61, 65-9. 

Zeolitic catalysts are commonly used for such purposes however, the modification of the acidity of the perovskite by addition of a second acidic oxide such as silica or alumina yields materials with balanced hy-drogenating-cracking functions that may be effective for selective hydrocracking. Barium zirconates were found to be materials particularly suited for use in catalytic hydrocracking of residua, especially for their ability for removal of carbonaceous deposits from the coked catalysts... 

A new method was developed, based on the original citrate route, which allows to synthesize perovskites with different incorporated metallic cations. Various catalysts based on the barium zirconate were prepared by this method. Perovskites were obtained containing either noble (Pd, Rh) or other metals (K, Cu, Mn). These systems were tested for several catalytic reactions, giving promising results. 

Athawale, A. A., Chandwadkar, A. J., Karandikar, R, Pasricha, R., Bapat, M. S. 2006. Radiation assisted synthesis of nanosized barium zirconate. Radiation Physics and Chemistry 75 755-759. 

With allowances for the actual metal content of zirconium (a small correction is also necessary for the hafnium content of about 2 /2%) and postulation of barium zirconate formation (see Table 27), reasonable accord between calculated and measured caloric output is established. However, the situation is more complex with boron mixtures where one encounters increase of heat output with increase of the percentage of boron in the mixtures much beyond the amounts of Equation (la). Thus, even with the reasonable assumption of secondary barium borate formation, the stoichiometry and heat output of the mixtures with more than about 10% of technical boron theoretical 8%) is obscure. Chromium boride formation may be a fector. 

Calculated from heat of formation of barium zirconate as cited by DOFL. >[Pg.289]

M. Koopman, S. Duncan, K. K. Chawla, and C. Coffin, Processing and characterization of barium zirconate coated alumina fibers/alumina matrix composites. Comp. Part A, 32 1039-1044 (2001). 

Barium Zirconate. BaZr03 m.p. 2620 C sp. gr. 2.63. Synthesized from barium carbonate and zirconia and used as an addition (generally 8-10%) to barium titanate bodies to obtain high dielectric constant (3000-7000) and other special properties. 

Chen CT, Danel CE, Kim S (2011) On the origin of the blocking effect of grain-boundaries on proton transport in yttrium-doped barium zirconates. J Mater Chem 21 5435-5442... 

Chen Z.C., Duncan S., Chawla K.K., Koopman M., Janowski G.M. Characterization of interfacial reaction products in alumina fiber/barium zirconate coating/alumina matrix composite. Mater. Characterization 2002 48 305-314... 

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