Bimetallic Alkoxides of Barium and Zirconium: Preparation of BaZrO3 Powder

Complex formation in solutions of barium and zirconium alkoxides in ROH (R=i-Pr, Et) was studied. A number of bimetallic complexes were isolated, and their structure and properties were studied. The sol-gel method yields a single-phase BaZrO₃ powder only wheni-PrOH solutions of the alkoxides are used. In this case, the oxocomplex, BaZrO(OPr-i)₄.(1–2)i-PrOH, is the precursor of the mixed oxide.     

Ferroelectric Thin Films of Bismuth Strontium Tantalate Prepared by Alkoxide Route

Study of the interactions in Bi(OR)3-Ta(OR)5-ROH (R = Me, Et, iPr) at 20°C show that metal ethoxides are the best of the investigated precursors for the production of bismuth tantalates via alkoxides. Polycrystalline SrBi2Ta2O9 (SBTO) and BiTaO4 films on Si-SiO2-Ti-Pt substrates with thicknesses of 0.4–0.5 m and 0.4 m, respectively, have been formed by sol-gel processing. The most stable solutions for film application were obtained by using mixed-metal Bi-Ta ethoxides and solutions of Sr carboxylate (2-ethylhexanoic acid derivative) in 2-ethylhexanoic acid. Films annealed at 700–750°C for 30 min were single-phased. SBTO films demonstrated good ferroelectric properties: remanent polarization ranged from 3.5 to 4.0 C/cm2 and coercive voltage 1.5–2.0 V, whereas BiTaO4 films showed dielectric behavior.     

Sol-Gel Derived Ferroelectric Thin Films: Avenues for Control of Microstructural and Electric Properties

The paper presents short review of the works performed during the last few years in the field of the alkoxy-derived ferroelectric films. PZT films were prepared using titanium and zirconium alkoxides and Pb(CH₃COO)₂· 2H₂O as precursors. Different way of lead acetate dehydration and the impact of lead excess in the precursor solutions on the properties of the PZT films are discussed. Trimetallic alkoxide systems Bi(OR)₃-Ta(OR)₅-ROH (R = Me, Et or ⁱ Pr) were studied as precursors for preparation of SrBi₂Ta₂O₉ films. Films prepared from these solutions and annealed at the temperature between 700 and 750°C demonstrated the remanent polarization P_r* – P^{^} _r = 7–9 C/cm². Ba_1-xSr_xTiO₃ films we applied from modified alkoxide solutions. Decomposition of the organic phase in the course of thermal treatment of the films is studied by IR-spectroscopy. The dependence of the dielectric permittivity of the films via the annealing temperature is reported. Preparation of LiNbO₃, SrZr_0.2Ti_0.8O₃, Zr_0.8Sn_0.2TiO₄ is briefly discussed.     

Oxoalkoxides—True precursors of complex oxides

X-ray structural analysis of crystalline alkoxides in many cases reveals that along with OR-groups their molecules also contain oxo-ligands. The following possible reactions leading to formation of oxoalkoxides have been discussed: hydrolysis, pyrolysis (frequently uncontrollable), ether elimination, oxidation of OR-groups (which exist in solutions of alkali, alkaline-earth and rare earth elements), or alkoxides of the lower oxidation states (which are formed by reduction of M(OR) _n on cathode during electrolysis or by hydrogen in statu nascendi). Oligomeric oxoalkoxides differ from the polymeric alkoxides M(OR) _n in considerably higher solubility and reactivity. The most important role of oxoalkoxides in the processes of formation of oxides has been demonstrated using as an example preparation of BaTiO₃ from alkoxides.     

The alkoxides of zirconium and hafnium: direct electrochemical synthesis and mass-spectral study. Do “M(OR)4”, where M=Zr,Hf, Sn,really exist?

The direct electrochemical synthesis of zirconium (1a) and hafnium (1b) alkoxides, M(OPrⁱ)₄·PrⁱOH, Zr(OBuⁱ)₄·BuⁱOH (4a) and M(OR)₄, where R=Et (2a,b), Buⁿ (3a), Bu^s (5a), C₂H₄OMe (6a,b) has been carried out by anodic oxidation of metals in anhydrous alcohols in the presence of LiCl as a conductive additive to give quantitative yields. The solubility polytherms and dissociation pressure of1a,b have been investigated. It has been proved by means of chemical analysis, X-ray powder, and IR spectral studies that the desolvation of 1a,b and Sn(OPrⁱ)₄·PrⁱOH (1c) is accompanied by the formation of amorphous oxocompounds M₃O(OPr_i)₁₀. On the basis of¹H NMR data it has been proved that the structure of the latter is analogous to that of known triangular cluster molecules M₃(₃-O)(₃-OR)(-OR)₃(OR)₆, where M=Mo, W, U. Mass-spectral data and the determined physicochemical characteristics of1–5 permit to conclude that the samples of composition M(OR)₄, where M=Zr, Hf, and2,3,5 contain tri- and tetranuclear oxocomplexes M₃O(OR)₁₀ and M₄O(OR)₁₄ respectively, along with Zr(OR)₄ oligomers of different molecular complexity.Deceased.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 752–760, April, 1995.