Jiangying Wang

Facile Synthesis of Highly Efficient p–n Heterojunction CuO/BiFeO3 Composite Photocatalysts with Enhanced Visible‐Light Photocatalytic Activity

A novel heterostructured CuO/BiFeO3 composite photocatalyst was successfully prepared through a simple combination of hydrothermal and impregnation process. CuO was uniformly deposited on the surface of BiFeO3 particles with a p–n heterojunction formed at the interface between CuO and BiFeO3. CuO/BiFeO3 heterostructured photocatalysts improved the UV/Vis spectral absorption ability, and exhibited enhanced photocatalytic activities for photodegradation of methylorange or a colorless compound (i.e., phenol) under visible light. In addition, after five recycles for the photodegradation of methylorange, CuO/BiFeO3 did not exhibit significant loss of photocatalytic activity, confirming its stability and long‐time reusability. The enhanced photocatalytic activity could be mainly ascribed to the p–n heterojunction structure between CuO and BiFeO3, which could significantly facilitate the separation and transfer of photogenerated electron–hole pairs. On the basis of the calculated energy bands, the photocatalytic mechanism was also proposed.

Infrared dielectric response and Raman spectra of tunable Ba0.5Sr0.5TiO3–Mg2TiO4 composite ceramics

Dielectric properties of (1−y)Ba0.5Sr05TiO3–yMg2TiO4 (y=0.5–0.8) composite ceramics were studied by using spectroscopic techniques. Increasing the concentration of Mg2TiO4 resulted in hardening of the softest mode, which is responsible for the decrease in the intrinsic permittivity and dielectric loss with increasing y. The soft mode hardens with y and becomes harmonic, which caused the reduction in tunability of the Ba0.5Sr05TiO3–Mg2TiO4 composite ceramics. Raman spectra revealed that linewidth of the MgO4 bending vibration decreases with increasing y, confirming the increase in intrinsic quality factor with y.

Raman and dielectric response of BaTi1-x(Mg1/3Nb2/3)xO3 solid solution

Structural evolution and dielectric analysis have been performed for BaTi1-x(Mg1/3Nb2/3)xO3 solid solutions with x ≤ 0.07, together with the analysis of Raman spectroscopy. X-Ray diffraction and Raman results show a structural evolution from a tetragonal phase to a cubic one with increasing x. Dielectric analysis reveals a low critical concentration corresponding to ferroelectric–relaxor crossover (xc = 0.05). Activation energy with dozens meV is obtained using the Vogel–Fulcher relationship, which is attributed to thermally activated off-center ion hopping.

Dielectric, ferroelectric and ferromagnetic properties of multiferroic (1-x)Ba0.99Ca0.01Zr0.02Ti0.98O3-xBiFeO3 ceramics

ABSTRACT Dielectric, ferroelectric and ferromagnetic properties of (1-x)Ba0.99Ca0.01Zr0.02Ti0.98O3 (BCZT)-xBiFeO3 (BFO) (x = 0.00, 0.05, 0.10, 0.15) ceramics have been investigated. X-ray diffraction and Raman data documented the tetragonal-to-pseudocubic phase transformation with increasing the concentration of BFO and the formation of BFO when the composition with x = 0.15 was sintered at 1100°C. Correspondingly, the samples showed a high temperature at permittivity maxima along with a weak frequency dispersion feature. Surprisingly, the composition with x = 0.15 exhibited weak ferroelectric and good magnetic properties with 2Mr∼0.60 emu/g, 2Hc∼0.36 kOe.

Dielectric Response of Ba0.5Sr0.5TiO3-Mg2SiO4 Composites Synthesized by a Citrate Gel In-Situ Process

(1-x)Ba0.5Sr0.5TiO3(BST)-xMg2SiO4 (MS) composite ceramics have been synthesized in-situ via a citrate-nitrate combustion process, and their structure and effective dielectric response have been investigated. The compositions with x ≥ 0.3 formed a second phase Ba2TiSi2O8, besides BST and MS phases. The BST-MS composites showed an uniform microstructure with MS particles homogeneously dispersed in BST particles. The temperature at the permittivity maxima of the composites was nearly unchanged with increasing the volume fraction of MS (ƒMS) from 0.1 to 0.4 and then slightly decreased with further increasing ƒMS. According to the modified effective medium approx-imation couple with the spherical inclusion model, the permittivity (ϵBST) of BST in the composites was strongly dependent on ƒMS, which was defined by the relation .

Controllable-permittivity and low-loss of Ba0.5Sr0.5TiO3/MgO composites prepared by citrate gel derived core-shell powders

Core-shell Ba0.5Sr0.5TiO3(BST)/MgO nano-composites have been synthesized by using an oleic acid modified citrate gel in situ process. The nano-composites exhibit a spherical microstructure consisting of large amounts of small particles with average sizes of 50-100 nm, which results in high F center levels in the composite ceramics. Interestingly, microwave permittivity of the composite can be reduced significantly with increasing volume fraction of MgO, while microwave loss and tunability remain almost unchanged, which is in good agreement with the results of the columnar model.