Papers by Author: Shao Jun Qiu

Abstract: Pb(Zr0.95Ti0.05)O3 powders were prepared by one-step pyrolysis process from non-aqueous Pechini method. Porous Pb(Zr0.95Ti0.05)O3 ceramics were obtained by sintering the chemically prepared powders and the grain growth in the porous ceramics was investigated. For the powders calcined at 450 °C for 10 h by one-step pyrolysis process, the grain growth exponent value was observed to be 3.3 while the apparent activation energy was 193 kJ/mol.

Abstract: Lanthanum-modified bismuth titanate, Bi3.25La0.75Ti3O12 (BLT), powders were prepared from polymerized precursors using citric acid as a chelating agent and ethylene glycol as an esterification agent. The effect of calcination temperature on the microstructure and morphology of powders were studied. It was shown that the pure and normally stoichiometric phase of BLT powders could be obtained at relative low temperature from 550o to 700oC even if the bismuth content is not excess in the starting precursors while the secondary phase could be detected at both lower and higher calcination temperatures. The shape of the BLT grains is also strongly influenced by the calcination temperature.

Abstract: Relaxor-based ferroelectrics, 0.65Pb(Mg1/3Nb2/3)O3-0.35PbTiO3 (PMN-PT) with a pyrochlore-free phase, was prepared by a modified polymerized complex process. The reactive columbite (MgNb2O6) phase was synthesized by the polymerized complex method at 1050oC for 4 h with 3wt% excess MgO. Lead acetate and tetrebutyl titanate were used to synthesize pyrochlore-free PMN-PT powder via the columbite route, from 800oC to 900oC, in air for 4 h. X-ray diffraction and scanning electron microscopy were used to detect the perovskite phase evolution and the presence of the pyrochlore phase in PMN-PT. The formation of perovskite PMN-PT is a function of the time and temperature conditions of the precursor calcinations, and an optimum condition for the thermal decomposition of the precursor was determined to avoid the formation of the pyrochlore phase.

Abstract: To adjust the morphology and crystallinity of the chemically prepared Zr-riched` lead zirconate titanate (Pb(Zr0.95Ti0.05)O3) powders, polyethylene glycol (PEG 20000) was used in aqueous solution (modified Pechini method). Thermal analysis of the as-synthesized gel showed two distinct stages, which indicates the volatilization of water and the decomposition of polymers, respectively. When the gel were calcined at 400 oC, the powders consisted mainly of perovskite PZT accompanied with small amounts of secondary phases. The higher the calcination temperature applied, the stronger the intensity of XRD, which means the crystallinity were improved. Scanning electron microscopy of as-prepared powders suggested that the powders were soft agglomerate particles when calcined at 600 to 800 oC. Compared with the normal Pechini method, PEG could help the formation of crystalline phase and soft agglomerate. When the powders compacts were sintered at 975 to 1125 oC, high pure (>99.5%) of tetragonal phase ceramics were got having relative density of 85% to 94%.

Abstract: A relaxor ferroelectric material, Pb(Mg1/3Nb2/3)O3 (PMN) powder with a pyrochlore-free phase, was prepared by using a one-step calcinations method. The pyrochlore phase was prevented by coating Mg(OH)2 on Nb2O5 particles. Pure-perovskite PMN powder was synthesized by a single calcination of the coating powder mixed with appropriate amounts of PbO at 900 oC for 2 h. The pyrochlore-free perovskite PMN powders were sintered to 96.9% density at 1100 oC. The sintered PMN ceramics exhibited a dielectric constant maximum of ~11 700 at room temperature at a frequency of 1 kHz.