Barium titanate precursor

A variety of related compounds, such as M(OSi(OR)3)4 (M = Hf and Zr) species has recently been studied, and some have been found to form stable aqua adducts below 10 °C.80-82 Another example is the barium titanate precursor, Ba2Ti2(acac)4 (OEt)g.83... 

Figure 13-19, SEM images of (a) a bare latex opal, (b) a latex opal infiltrated with a barium titanate precursor and (c) a barium titanate inverse opal obtained at 750 C (Soten, 2002).

TEM of barium titanate precursor obtained by aging a solution containing Ti(lV) iso-propoxide at (a) 60°C for 2 hours or (b) 40°C for 2 hours. From Matijevic and Gherardi [163). See also discussions in Chapters 2 and 4. 

Figure 21.8 Time-resolved SAXS patterns of drying barium titanate precursor film with [Ti] = 0.5 mol r and [H20]/[Ti] = 5.6 at 60 °C. Experimental data are fitted with double...

Hennings, D. Rosenstein, G. Schreinemacher, H. 1991. Hydrothermal preparation of barium titanate from barium-titanium acetate gel precursors. J. Euro. Ceram. Soc. 8 107-115. 

The products of the precursor method are usually crystalline solids, often containing small particles of large surface area. For some applications, such as catalysis and barium titanate capacitors, this is an advantage. 

Barium titanate and BaTi03-based materials are most commonly used for ceramic capacitors with high dielectric permittivity. BaTi03 powder of extremely high quality (in respect of its purity, stoichiometry, particles morphology) is required for most of the modem applications. This characteristic may be considerably improved by the application of alkoxide precursors. Thus, it is of no surprise that synthesis of BaTi03 and BaTi03-based materials from metal alkoxides attracted considerable attention for several decades. The first works on... 

If the cations of interest, Ba2+ and Ti4+ in the case of barium titanate, can be obtained in solution in the correct ratio then precursors to the final required product can be formed. Subsequent heating of the precursors leads to the formation of BaTi03 (BT) involving the minimum of ion diffusion distances. Because of this the oxides can be formed at relatively low temperatures, for example 500 °C rather than the usual > 1000 °C necessary to effect the solid state reaction between mixed oxides. 

This is a relatively low-temperature, water-based route capable of producing submicron, spherical and uniform sized particles of either high purity or chemically modified BT. Essentially barium, titanium and dopant compounds are reacted in a basic aqueous medium to form hydroxides. Under the hydrothermal conditions, typically in the temperature and pressure ranges 100-250 °C and 100kPa-3MPa ( —30 atm) respectively, sub-micron particles of either pure or modified barium titanate are precipitated. There are many variables which need careful control, especially the reactive areas of the precursors and the degrees of supersaturation of the various species. 

All the aforementioned precursors are pivotal to the development of nonsupercon-ducting metal oxide films such as the barium titanates, barium tantalates, and tantalum... 

The inverse-micelle approach may also offer a generalized scheme for the preparation of monodisperse metal-oxide nanoparticles.The reported materials are ferroelectric oxides and, thus, stray from our emphasis on optically active semiconductor NQDs. Nevertheless, the method demonstrates an intriguing and useful approach the combination of sol-gel techniques with inverse-micelle nanoparticle synthesis (with /Hoc/erate-temperature nucleation and growth). Monodisperse barium titanate, BaTiOs, nanocrystals, with diameters controlled in the range from 6-12nm, were prepared. In addition, proof-of-principle preparations were successfully conducted for Ti02 and PbTiOs. Single-source alkoxide precursors are used to ensure proper stoichiometry in the preparation of complex oxides (e.g. bimetallic oxides) and are commercially available for a variety of systems. The... 

Figure 40.4 shows the SEM images of barium titanate powders synthesized at 850°C. The effect of using various barium concentration and precursor sources for titanium was studied [3] In Fig. 40.4a barium concentration is 0.3 mol/L and titanium source is Ti02 sols, in Fig. 40.4b barium concentration is 0.03 mol/L and the titanium source is the same as above, i.e., Ti02 sols in Fig. 40.4c the barium concentration is 0.3 mol/L the same as Fig. 40.4a, but the titanium source is the TiCl4 precursor. When a high concentration of barium was used (0.3 mol/L), the particles were spherical with diameters of 200-500 nm (Fig. 40.4a), whereas for a low concentration of 0.03 mol/L the particle diameter is from 100 to 200 nm (Fig. 40.4b). Therefore, the particle diameter of the barium titanate may be controlled by the metal ion concentration in the emulsion droplet. Particles in Fig. 40.4c exhibited a broader particle size distribution [3]. The diagram of Fig. 40.2 and the discussion provided later may help interpret the results observed in Figs. 40.3 and 40.4.

Ozen M, Mertens M, Luyten J, Snijkers F, D Hondt H, Cool P (2012) Hydrothermal S3mthesis of carbonate-free submicron-sized barium titanate from an amtnphous precursor S3mthesis and characterization. Ceram Int 38 619-625... 

Moon, J., Suvaci, E., Li, T., Sostantino, S.A., Adair, I.H. Phase development of barium titanate from chemically modified amorphous titanium (hydrous) oxide precursor. J. Eur. Ceram. Soc. 22, 809-815 (2002)... 

The second class of sol-gels contains redox-active metal oxides, such as tungsten oxide, vanadium pentoxide, manganese oxide, and other transition metal oxides. Moreover, many n-type semiconductors such as zinc oxide, barium titanate, and titanium dioxide can be used in this class (113). The structures of these gels are sensitive to the pH and oxidation state of the precursors. Many redox-active sol-gels exhibit electrochromism (different oxidation states exhibit different colors, allowing spectroscopic determination of redox states). These gels can also accommodate the reductive insertion of lithium and other moieties. 

Synthesis of barium titanate powders by aerosol pyrolysis of a Pechini-type precursor solution./. Mater. Chem.,... 

Kakihana M., Yoshimura M. Synthesis and characteristics of complex multicomponent oxides prepared by polymer complex method. Bull. Chem. Soc. Jpn. 1999a 72 1427-1443 Kakihana M., Arima M., Nakamura Y., Yashima M., Yoshimura M. Spectroscopic characterization of precursors used in the Pechini-type polymerizable complex processing of barium titanate. Chem. Mater. 1999b 11 438-450... 

An aqueous precursorfor 0.75Pb(Zni/3- Nb2/3)O3-0.25BaTiOs solid solution was synthesized by Van Werde et al. (2001). They used acetates of lead and zinc, and Nb(V) peroxocitrato complex. The solution of lead zincate niobate was prepared by adding the compounds into aqueous solution of ammonium citrate. The aqueous solution was stable when pH was higher than 8 and the citrate acid/cation mole ratio was higher than 1.5. The aqueous precursor for barium titanate was prepared by using titanium(IV) peroxocitrato complex and barium acetate. They found that the solid solution of PZN and BT is crystallized as a perovskite phase at temperatures as low as 800°C. 

XRD patterns, 86 polymeric precursors, 59 polymeric siloxanes, 401 polymerizable complex (PC) method for barium titanate synthesis, 82 for photocatalysts synthesis, 93 use of, 77... 

BaTiOs nanopowders were synthesized from the alkoxide solution precursor by the sol-gel process [99]. The barium titanate sol synthesis route employed... 

Stawski, T.M., Veldhuis, SA., Besselink, R., Castricum, HX., Portale, G., Blank, DJIA, and ten Elshof, JX. (2012) Nanostructure development in alkoxide-carboxylate-derived precursor films of barium titanate. /. Phys. Chem. C, 116, 425 34. 

Nanoscale structure evolution in alkoxide-carboxylate sol-gel precursor solutions of barium titanate. / Phys. 

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