Papers by Author: Jing Zhou

Abstract: A piezoelectric generator based on the piezoelectric stacked elements is applied to realize electro- mechanical energy conversion in this paper. The piezoelectric stacked generator is constructed. The relational expression about output electrical characteristic parameters, the constructional dimension parameters of piezoelectric stack elements and external driving forces is discussed here. Theoretical predictions confirmed by experimental results show that the piezoelectric generator produces electrical power with higher efficiency, and energy harvesting circuit can harvest energy from the piezoelectric generator effectively.

Abstract: In this work, 1-3 composites, which required for different devices applications, with the (PZT)-based (PZT-5, PMnS-PZN-PZT and PSN-PZN-PZT) piezoelectric fibers produced via a VPP method have been investigated. The relationship between the dielectric and piezoelectric properties of the 1-3 composites and different ceramic fibers with various aspect radios has been compared. We conclude that the properties of the 1-3 composites are well followed with the properties of the piezoelectric fibers, so the performance of the 1-3 composites can be improved for various devices by tuning the fiber properties.

Abstract: Effect of stacking layers on the structure and properties of Ca(Mg1/3Nb2/3)O3/CaTiO3 (CMN/CT) microwave dielectric heterogeneous thin films prepared was investigated. Precursor solutions for CMN and CT synthesis were obtained by Pechini method. The arrangement pattern has affected structure and properties of heterogeneous thin film. The CMN-CT arrangement heterostructure thin film has second phase from the CMN films layer. The CT-CMN heterostructure film which has a smooth and dense microstructure was composed of pure perovskite phase without any second phase, this result was attributed to the CT film layer which is a buffer layer between substrate and CMN film layer. At 1MHz frequency, CT-CMN exhibits the dielectric properties of εr=47.5, tanδ=0.020.

Abstract: The relationship between the character of the B-site cation–oxygen bond and the microwave dielectric properties in perovskites dielectric materials was studied in this paper. The atomic net charge of CaTiO3 (CT) and Ca(Zn1/3Nb2/3)O3 (CZN) was calculated respectively. The calculating result implies that the covalency of B-O bonds in CZN is stronger than that in CT. This predicted that the dielectric constant and loss of the ceramics will decrease after CZN incorporated in CT. To confirme the prediction, (1-x)CT-xCZN microwave dielectric ceramics were prepared by solid state reaction method with ZnNb2O6 as precursor. The structure analysis in terms of tolerance factor gives an identical result as calculation. The microwave dielectric properties, such as dielectric constants, Q×f values and τf were studied as a function of composition. With x increasing from 0.2 to 0.8, the dielectric constant linearly decreases from 109 to 49.37, the Q×f value increases from 8,340 to 13,200 GHz, and τf decreases from 321 to -18 ppm/°C. The properties trends are consistent with the previous calculation results, and confirm the relationship between the character of B-O bond and dielectric properties.

Abstract: A new kind of functionally graded materials (FGM) with density gradient has come to show great potentials as flier-plates for creating quasi-isotropic compression waves. In order to meet the demand of lower density in the front face and wider density range for such flier-plate, Mg with a density of 1.74g/cm3 and W of 19.3g/cm3 are selected to make Mg-W system density graded materials. Mg-W alloys with various mass fractions of Mg and W were sintered by spark plasma sintering (SPS) technique at low temperatures, and the processing of densification is mainly investigated. It is found that, up to 92wt%W, the Mg-W alloys can be fully densified at 873K due to the conglutination of Mg particles. The Mg-W alloys still exist as a mechanical mixture of Mg and W. Finally, the Mg-W density graded materials with a density change from 1.74g/cm3 to 10.55g/cm3 have been successfully prepared.

Abstract: Ca(Al1/2Nb1/2)O3 (CAN) and Ca(Fe1/2Nb1/2)O3 (CFN) were prepared by solid reaction route. With the sintering temperature increased, the Q×f value of CAN changes from 7 200 to 17 500 GHz due to the changing of the ordering degree, whereas, the dielectric constant and Q×f value of CFN decrease remarkably without structural changing. The reason of this phenomenon is that the difference in size of two B-site ions in CAN is larger than that in CFN. As a result, the ordering degree of CAN is more sensitive to the conditions of sample preparation, compared with CFN.

Abstract: Using Zr(NO3)4.5H2O as Zr source, PZT powder with a single-phase perovskite structure was synthesized by a sol-autocombustion method at a calcining temperature of 700°C. Compared with a solid-state reaction method, the calcining temperature of PZT can be lowered by 200°C when using the sol-autocombustion method. PMZN ceramic was prepared at a sintering temperature of 1050°C with the resulting PZT powder as a base, which can lower the sintering temperature by 150°C. The microstructure of the PMZN ceramic was investigated by XRD and SEM, and the dielectric and piezoelectric properties were measured. The results showed that the PMZN piezoelectric ceramic has a tetragonal perovskite structure, showing the main electrical properties as follows: Kp = 0.54, Qm = 1073, tgd £ 0.001, e33 T/ e0 = 1236, d33 = 454pC/N, and fs =136.1KHz.

Abstract: The electron structure of Pb(Zr1/2Ti1/2)O3(PZT), Pb(Zn1/3Nb2/3)O3(PZN) and Pb(Mn1/3Sb2/3)O3 (PMS) systems was calculated by the SCF-DV-Xα calculation method. The effects of ABO3-type perovskite and pyrochlore ceramic electron structure on their piezoelectricity were also studied. The results showed that the ferroelectric phase is more stable than paraelectric phase and the necessary condition of stable existing ferroelectric is the mixed orbit of O2p orbit and the out layer d orbit of B-site atom. The stability of ferroelectricity can be indicated by the strength of mixed orbit. When (Zr, Ti) was substituted by Mn1/3Sb2/3, Zn1/3Nb2/3, if it could form tetragonal perovskite structure, the total system energy would reduce and the mixed orbit will enhance, which improves the ferroelectricity of PZT system. However, if it forms a cubic pyrochlore structure, the ferroelectricity would lose because the covalent bond strength of B-O (axial direction) and B-O (vertical axial direction) is different obviously, which lead to the system structure become unstable.

Abstract: xPb(Ni1/3Nb2/3)O3-yPb(Mn1/3Nb1/3Sb1/3)O3-(1-x-y)Pb(Zr0.48Ti0.52)O3 ceramics have been prepared by a columbite two-step method. NiNb2O6, MnNb2O6 and MnSb2O6 were used as precursors to produce the pseudoquintnary system ceramics. X-ray diffraction (XRD) results indicate that the pseudoquintnary system ceramics have a single-phase perovskite structure. The piezoelectric and dielectric properties of the ceramics were investigated as functions of x or y. The addition of Pb(Ni1/3Nb2/3)O3 makes the piezoelectric properties
to become ‘soft’, while the addition of Pb(Mn1/3Nb1/3Sb1/3)O3 makes the piezoelectric properties to be ‘hard’. The Curie temperature (Tc) of the pseudoquintnary system decreases with the increase of Pb(Ni1/3Nb2/3)O3 or Pb(Mn1/3Nb1/3Sb1/3)O3 contents. The preferred piezoelectric properties were obtained in the composition with x=0.06 and y=0.06.