Zuyong Feng

Aging effect evolution during ferroelectric-ferroelectric phase transition: A mechanism study

Aging can significantly modify the dielectric, piezoelectric, and ferroelectric performance of ferroelectrics. However, little attention has been paid to the aging effect during ferroelectric-ferroelectric phase transitions that is essentially correlated with real applications. In this letter, the authors report the aging effect evolution between two ferroelectric phases in an acceptor-doped piezoceramics. The results show that aging-induced double hysteresis loops were exhibited in different ferroelectric phases, but disappeared during ferroelectric-ferroelectric phase transitions, suggesting the mechanism that the intrinsic restoring force for the reversible switching of domains caused by the alignment of defect dipoles was weakened due to ferroelectric dipole reorientation.

Large piezoelectric effect in low-temperature-sintered lead-free (ba0.85ca0.15)(zr0.1ti0.9)o-3 thick films

High-quality piezoelectric (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 thick films with dense and homogenous microstructures were fabricated at a low sintering temperature (900°C) using a CuBi2O4 sintering aid. The 10 μm thick film exhibited a high longitudinal piezoelectric constant d33,eff of 210 pC/N with estimated unconstrained d33 value of 560 pC/N very close to that in the corresponding bulks. Such excellent piezoelectric effect in the low-temperature sintered (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 thick films is comparable to the case of lead-based PZT thick films, and may be a promising application in lead-free microdevices such as piezoelectric microelectromechanical systems (MEMS).

Influence of Sodium Carbonate Amount on Crystalline Phase and Structure Stability for Doping Nickel Hydroxide

Alpha nickel hydroxide has better performances than commercial beta nickel hydroxide. However, the main defect is that α-phase is difficult to synthesize and easily transformed to β-phase Ni(OH)2 upon aging in a strong alkaline solution. In this study, the Al-Co, Al-Yb, Yb-Co and Al-Yb-Co multiple doping was used respectively. By controlling the amount of sodium carbonate, the α-Ni(OH)2 was prepared by ultrasonic-assisted precipitation. And the influence of sodium carbonate on the crystalline phase and structure stability for alpha nickel hydroxide was studied. The results demonstrate that, with increasing amount, the biphase nickel hydroxide transforms to pure alpha nickel hydroxide gradually, and the structure stability is also improved. When the amount of sodium carbonate is 2 g, the sample still keeps α-Ni(OH)2 after being aged for 30 days, for Al-Yb-Co-Ni(OH)2. And when the amount is less than 2 g, the phase transformations exist in the samples with different extents. These results demonstrated that the amount of sodium carbonate is a critical factor to maintain the structural stability of α-Ni(OH)2.

Luminescence and cathodoluminescent properties of monoclinic Y2WO6 co-doped with Dy-Bi

Dy-Bi co-doped yttrium tungstate crystal materials were synthesized by high temperature solid-state method. To reveal the photoluminescence features and properties of the samples, some measurements have been taken. It turned out that different Bi3+ concentrations play obvious influence in emission performance, and show visible light emission under ultraviolet light excitation. Besides, the effect of temperature on phase structure of samples has also been studied here. Superhigh X-ray luminescence of the phosphors exhibited the promising application in the field of high energy detection. The X-ray irradiation crystal resistance stability of the phosphors has also been investigated through the subsequent testing of XRD and spectra.

Photoluminescence and Photocatalytic Activity in Ca2+ and Dy3+ Co-doped ZnWO4 System

Ca2+ and Dy3+ co-doped ZnWO4 system was synthesized successfully via high temperature solid-state reaction. The photoluminescent, X-ray diffraction (XRD), and photocatalytic properties of the phosphors had been studied systematically. The results indicated that Ca2+ and Dy3+ co-doped ZnWO4 phosphors have lower luminescent intensity than that of ZnWO4: Dy3+ phosphors. The result of UV-Vis diffuse reflectance spectra demonstrated that Ca2+ and Dy3+ co-doped ZnWO4 phosphors show higher UV absorption efficiency. In addition, photocatalytic activities of the Ca2+ and Dy3+ co-doped ZnWO4 phosphors were evaluated by photo-degradation of RhB under ultraviolet irradiation. The result shows that Ca2+ and Dy3+ co-doped ZnWO4 phosphors can exhibit higher photocatalytic activity than pure ZnWO4:Dy3+, which could be ascribed to more electron-hole pairs generated and the combination of electrons and holes decreased in the co-doped phosphors. Thus, resulting in the increase of photocatalytic activity.