Barium titanate powder

Table 2. Commercial Hydrothermal Barium Titanate Powders ...

Fine chemicals These are produced in small volumes and purchased on the basis of chemical composition, purity and price. Examples are chloropropylene oxide (used for the manufacture of epoxy resins, ion-exchange resins and other products), dimethyl formamide (used, for example, as a solvent, reaction medium and intermediate in the manufacture of pharmaceuticals), n-butyric acid (used in beverages, flavorings, fragrances and other products) and barium titanate powder (used for the manufacture of electronic capacitors). 

There are four principal routes to producing barium titanate powders. 

John Wang, Jiye Fang et al., Ultrafme barium titanate powders via microemulsion proessing routes. J. Am. Ceramic Soc. 82(1999) pp.873-881. 

Blanco-Lopez, M.C., Rand, B., and Riley, RL., J. Ear. Ceram. Soc., 17, 281,1997. Lu, S., Lee, B.I., and Wang, Z., Synthesis of redispersible nano-sized barium titanate powders by hydrothermal method, in Ceramic Transactions, vol. 106, Dielectric Materials Devices, edited by K.M. Narr and A.R. Bhalla, American Ceramic Society, Westerville, OH, 2000. 

Blanco-Lopez, M.C.. Fourlaris, G., and Riley, EL.. Interaction of barium titanate powders with an aqueous suspending medium. 7. Eur. Ceram. Soc., 18, 2183, 1998. 

Phule, D. P., and Risbud, S. H., Sol-gel synthesis of barium titanate powders using barium acetate and titanium(IV) isopropoxide, Adv. Ceram. Mat., 3, 183 (1988). 

Mazdiyasni, K. S., Effects of dispersion of barium titanate powder on measure ments in an electrical-sensing-zone particle size counter. Am. Ceram. Soc. Bull 57, 448 (1978). 

The slurry formulation for tape casting barium titanate sheets consists of the following ingredients barium titanate powder, phosphate ester, methyl ethyl ketone, ethanol, acrylic resin, benzyl butyl phthalate, and poly(ethylene glycol), (a) Explain the function that each of the ingredients has in the formulation, (b) What would be the usual amounts (in wt%) of each of the ingredients in a typical tape cast formulation ... 

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.

Fig. 40.4 SEM images of barium titanate powders synthesized at 850°C. (a) Barium concentration is 0.3 molA- and titanium source is Ti02 sols (b) Barium concentration is 0.03 mol/L and titanium source is Ti02 sols (c) Barium concentration is 0.3 mol/L and titanium source is TiCl4. (Reprinted from [3] with permission. Copyright 1999 Springer)...

Fig. 5.14 Sonochemically prepared nanosize barium titanate powder [272]...

An example of kinetic optimization is the nanosize barium titanate powder with specific surface area of 38 0 m /g and particle size of 25-30 nm. According to electron microscopy the dispersion range was a little broader (around 8-40 nm,... 

Chien, A.T., Speck, J.S., Lange, F.F., Daykin, A.C., Levi, C.G. Low temperature/low pressure hydrothermal synthesis of barium titanate powder and heteroepitaxial thin films. J. Mater. Res. 10, 1784-1789 (1995)... 

Mazdiyasni, K.S., DoUoff, R.T., Smith II, IS. Preparation of high-purity submicron barium titanate powders. J. Am. Ceram. Soc. 52, 523-526 (1969)... 

Ragulya, A.V., Vasyl kiv, O.O., Skorokhod, V.V. Synthesis and sintermg of nanociystaUine barium titanate powder under non-isothermtd conditions I. Control of dispersity of barium titanate during its synthesis from btirium tittmyl-oxtdate. Powder Metall. Metal Ceram. 36(3/4), 170-175 (1997)... 

Ragulya, A.V. Rate-controlled synthesis tmd sintering of nanocrystaUme barium titanate powder. Nanostruct. Mater. 10,349-355 (1998)... 

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

Arima M., Kakihana M., Nakamura Y., Yashima M., Yoshimura M. Polymerized conplex route to barium titanate powders using barium-titanium mixed-metal citric acid complex. J. Am. Ceram Soc. 1996 79 2847-2856... 

Barium titanate powders were produced using either an amorphous hydrous Ti gel or anatase precursor in a barium hydroxide (Ba(OH)2) solution via a hydrothermal technique in order to discern the nucleation and formation mechanisms of BaTi03 as a function of Ti precursor characteristics. Isothermal reaction of the amorphous Ti hydrous gel and Ba(OH)2 suspension is believed to be limited by a phase boundary chemicd interaction. In contrast, the proposed BaTi03 formation mechanism from the anatase and Ba(OH>2 mixture entails a dissolution and recrystallization process. BaTi03 crystallite nucleation, studied using high resolution transmission electron microscopy, was observed at relatively low temperatures (38°C) in the amorphous hydrous Ti gel and Ba(OH)2 mixture. Additional solution conditions required to form phase pure crystallites include a C02-free environment, temperature >70°C and solution pH >13.4. Analysis of reaction kinetics at 75°C was performed using Hancock and Sharp s modification of the Johnson-Mehl-Avrami approach to compare observed microstructural evolution by transmission electron microscopy (7). 

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