Papers by Author: Zhi Yong Yu

Abstract: Steady organic-inorganic perovskite hybrids with (H22-Ap)3/2Fe(CN)6, (H23-Ap)3/2Fe(CN)6 and (H24-AP)3/2Fe(CN)6 (2-AP = 2-aminopyridine, 3-AP = 3- aminopyridine, 4-AP = 4- aminopyridine) were formed from aqueous solution. Each structure was an unusual layered organic-inorganic structural type. A device was designed to construct electrochemical sensing devices using above organic-inorganic perovskite hybrids. The sequence of redox activity is (H24-Ap)3/2Fe(CN)6 > (H22-Ap)3/2Fe(CN)6 > (H23-AP)3/2Fe(CN)6 and that of electrocatalytical activity is (H22-Ap)3/2Fe(CN)6 > (H23-Ap)3/2Fe(CN)6 > (H24-AP)3/2Fe(CN)6. The variation coefficients (RSD) of successive and interval assays are less than 2.0%. Three electrochemical sensing devices display a remarkable electrochemical sensitivity and stability.

Abstract: The energy storage density of (1-x) BaTiO3 – x Ba(Mg1/3Nb2/3)O3 (x = 0, 0.1, 0.2, 0.3) ceramics was investigated. The microstructure of samples was characterized by scanning electron microscopy (SEM). The energy storage density was calculated from the P-E hysteresis loops measured at room temperature. Experimental results show that the energy storage density of 0.9 BaTiO3 – 0.1 Ba(Mg1/3Nb2/3)O3 ceramics is highest among all compositions. At 15.8kV/mm electric field, the energy storage density of the sample can reach up to 1.07J/cm3, which is about 1.5 times higher than pure BaTiO3. The improvement of the energy density can be due to two factors: one is the improved breakdown strength caused by the optimized microstructure, the other is the decreased remnant polarization. This result indicates that bulk 0.9 BaTiO3 – 0.1 Ba(Mg1/3Nb2/3)O3 ceramic has advantages compared with pure BaTiO3 ceramic for energy storage applications, and with further improvements in microstructure and reduction of sintering temperature, could be a good candidate for energy storage capacitors.

Abstract: Temperature-dependent Raman scattering, dielectric properties, and Impedance spectra have been carried out on Ba(Ti0.8Sn0.2)O3 ceramic sample. The number of modes observed for the compositions of cubic symmetry is more than that predicted by group theory, and the A1(TO1) and E(TO2) modes become Raman active below the critical temperature (around 300K) in the lower frequency region. This gives evidence that there are some deviations of the local structure from the average global symmetry. Moreover, The characteristic of A1(TO3) mode is confirmed be associated with the diffused dielectric properties. Impedance/modulus analyses indicate that a third resistance-capacitance (RC) response is present in the sample, in addition to the grain and grain-boundary RC elements above 573K. Thus, it probably inferred that the existence of inter- and/or intra-granular surface layers associate with the abnormal dielectric properties, which is different from the normal ferroelectrics. Variation of bulk ac conductivity as a function of temperature shows that Ba(Ti0.8Sn0.2)O3 follows the classical Arrhenius relation.The results show that the activation energy of grains and grain boundaries are 0.61 and ~1.08 eV, respectively.

Abstract: (1-x)(K0.44Na0.52Li0.04)(Nb0.84Ta0.10Sb0.06)O3-xSrTiO3 (KNNT-ST) lead free piezoelectric ceramics have been synthesized by a solid state reaction method. The effect of SrTiO3 content on the piezoelectric properties, sintering behavior and microstructure of (1-x) KNNT-x ST ceramics was investigated. The experimental results showed that the addition of SrTiO3 can restrain the volatilization of Na ions and K ions and improve relative density of the samples. A morphotropic phase boundary between orthorhombic and tetragonal phases is found in the composition range of 0.03

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