Papers by Author: Yi Hua Deng

Abstract: The dispersion and stability of PZT aqueous suspensions were investigated by using ammonium salt of polyacrylic acid (PMAA-NH4) as the dispersant. By observing the sedimentation behavior and measuring the viscosity, the effects of dispersant concentration and pH value on the dispersion and stability of the suspensions were studied. The experiment results showed that the optimum concentration of PMAA-NH4 and the optimum pH were 0.25-0.45 wt.%( by weight of the PZT powders) and 8.5-10, respectively. When the dispersant concentration was about 0.45 wt.%, and pH value was about 9.4, the stable PZT suspensions with high solids loading (up to 52 vol.%) and low viscosity (<1Pa.s) was obtained for gelcasting. The microstructure of ceramic formed by gelcasting was denser and more homogeneous than that by die pressing.

Abstract: The influences of the substitution of (Zn1/3Nb2/3) group for Ti as well as addition of Fe2O3 and K2CO3 on d33, kp, εr, and tgδ of the Pb[Zr0.46Ti0.54-x(Zn1/3Nb2/3)x]O3 + y mol%Fe2O3+z mol%K2CO3 (PZNPZT) (0 ≤ x ≤ 0.20, 0 ≤ y ≤ 0.10, 0 ≤ z ≤ 0.20) ceramics were investigated. The experimental results demonstrated that when x increases in Pb[Zr0.46Ti0.54-x(Zn1/3Nb2/3)x]O3+0.3 mol%Fe2O3+0.5mol%K2CO3 ceramics, the d33, kp, εr, and tgδ increase and approach to their maximum values, then eventually decrease. XRD analysis revealed that the perovskite structure of the materials transfers from tetragonal phase to rhombohedral phase. The relative dielectric constant (εr) decreases dramatically in the rhombohedral phase area near the MPB; the d33 and εr decrease with the small amount of added Fe2O3 and K2CO3, which also contributes to densification of the PZN-PZT ceramics. The optimized piezoelectric performances through the experiment were obtained as d33=280 pC/N, kp=0.62, εr=900, tgδ=0.003.

Abstract: (Na0.5Bi0.5)TiO3 (Abbreviated to BNT) was synthesized by hydrothermal process and the average gain size was 15 nm with narrow size distribution. Pure perovskite structure of BNT particles was identified by XRD analysis. The nanoscale BNT powder was selected as raw material to fabricate BNT based ceramics with BaTiO3 (Abbreviated to BT) and Ba(Cu0.5W0.5)O3 (Abbreviated to BCW) doping. SEM images show that the ceramic using nanoscale BNT powder as raw material has a high dense body with the average gain size from 0.5 μm to 1 μm. The experimental results show that with increasing amount of BCW, d33 and Kp of (0.94-x)BNT-0.06BT-xBCW increase initially, then reach the maximum values of 130 pC/N and 0.32 when 5mol% of BCW was added. Further increasing amount of BCW leads to decreasing d33 and Kp. The optimal piezoelectric and dielectric properties were obtained as d33 = 130 pC/N, Kp = 0.32, εr = 800, tgδ = 0.06.