A homogeneous and stoichiometric fine powder of the piezoelectric oxide Pb(Zr0.52Ti0.48)O3(PZT) has been prepared by the hydroxide coprecipitation route. By considering the thermodynamic equilibrium constants, the solubility and ionic equilibria relationships for individual metal hydroxides in aqueous media could be theoretically evaluated as a function of solution pH and metal ion concentration. An optimal pH of 9 for the coprecipitation of the ternary Pb-Zr-Ti system as hydroxides was predicted from the solubility diagrams, and the quantitative coprecipitation of metal hydroxides was confirmed experimentally. Pb(Zr0.52Ti0.48)O3 as a single phase was obtained by thermal decomposition of the coprecipitated hydroxide precursor above 500 °C. The calcined powders at various temperatures were characterized by inductively coupled plasma (ICP) studies, thermogravimetry-differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) surface area measurements.

Hydroxide coprecipitation route to the piezoelectric oxide Pb(Zr,Ti)O3(PZT)

Preparation and magnetic properties of ultrafine SrFe12O19 particles derived from a metal citrate complex

Highly reactive and ultra-fine barium polytitanates (BaO-nTiO2, n= 4, 4.5, 5) with a particle size of 30–50 nm have been prepared by the citrate route. Solubility isotherms were calculated for the BaCO3-citric acid-H2O and TiO(OH)2-citric acid-H2O2-H2O systems at 25 °C to predict the optimum pH condition for preparing pure and stable citrate complexes. Pure and well crystallized powders with monodispersive, nanometer-sized particles could be obtained by thermal decomposition of the optimally prepared citrate precursors at relatively low temperatures. Details of the crystallization process and particle characteristics of citrate-derived barium polytitanates are described. The sinterability and microwave dielectric properties of BaTi4O9 and Ba2Ti9O20 were also measured and are discussed briefly.

Citrate route to ultra-fine barium polytitanates with microwave dielectric properties

Dissolution of BaCO 3 and its effect on the dispersion behavior of aqueous BaCO 3 suspensions at various pH values have been investigated. The amount of leached Ba 2+ decreases with increasing pH value, which agrees with thermodynamically calculated results. The dissolution of BaCO 3 also causes an increase in pH value of the suspension, but the change decreases with increasing initial pH value. The isoelectric point (IEP) of leached BaCO 3 powder is at a pH of ∼10-10.5 and remains unchanged with increasing solids loading. The IEP of BaCO 3 shows no significant change with added KCI or K 2 CO 3 , but shifts to a higher pH with increasing concentration of added BaCl 2 .

Dissolution and Dispersion Behavior of Barium Carbonate in Aqueous Suspensions

Citrate sol-gel method for the preparation of β/β′'-alumina

Optimization of precursor fiber formation conditions from the Y-Ba-Cu-citric acid-H2O sol

In order to synthesize high-purity alpha alumina fine powder, the aluminum hydroxide and ammonium aluminum sulfate(alum) precursor were prepared from natural alumino-silicate(halloysite). The thermal decomposition mechenism for both precursors was elucidated by DTA/TG, XRD and IR analysis. The microstructure, specific surface area and purity of were characterized by SEM, and BET analysis. The particle size of was determined to be = 0.1∼0.5 m. However, the specific surface area for the alum derived (89.0 m/g) was extremely higher than that for the aluminum hydroxide derived one(7.3 m/g).

https://www.koreascience.or.kr:443/article/JAKO199113464511491.pdf

Yoo Jong-Seok

Papers

Optimization of precursor fiber formation conditions from the Y-Ba-Cu-citric acid-H2O sol

Alum and Hydroxide Routes to ${\alpha}-Al_2O_3$ (II) Ultra-Fine Alumina by Thermal Decomposition