Dong-Yun Guo

Effects of ion doping at different sites on electrical properties of multiferroic BiFeO3 ceramics

Pure, La3+ doped at A site, V5+ doped at B site, and La3+ and V5+ co-doped multiferroic BiFeO3 ceramics: BiFeO3 (BFO), Bi0.85La0.15FeO3 (BLF), BiFe0.97V0.03O3 (BFV), Bi0.85La0.15Fe0.97V0.03O3 (BLFV), etc were successfully prepared by a rapid liquid sintering technique. X-ray diffraction indicated that these ceramics were of polycrystalline perovskite structures, accompanied with a tiny residual Bi2O3 phase. It was found that, among these ceramics, BLFV ceramic exhibited the best electrical properties. The leakage current density of BLFV ceramic was only 2.1 × 10−6 A cm−2 at 10 kV cm−1, two and one orders of magnitude lower than those of the BLF and BFV ceramics, respectively. In the measuring frequency of 4 KHz–1 MHz, the dielectric constants and losses of this sample exhibited slight variation and the lowest loss tangent was 0.08. The sample had a relatively saturated ferroelectric hysteresis loop. These suggested that the co-doped BiFeO3 ceramic by La3+ and V5+ at A and B sites showed advantages in application over the pure BFO, doped BLF and BFV ceramics, respectively.

Enhanced electrical properties in multiferroic BiFeO3 ceramics co-doped by La3+ and V5+

La3+ and V5+ co-doped Bi0.85La0.15Fe1?xVxO3 (BLFVx, x = 0?0.1) ceramics were prepared by a rapid liquid sintering technique. The effects of the V5+-doping content on the structure and electrical properties of BLFVx ceramics were investigated. In the range of the V5+ content x from 0 to 0.03, BLFVx ceramics had a polycrystalline perovskite structure with tiny residual Bi2O3, while an impurity phase appeared for x > 0.03. As the x increased from 0 to 0.1, both the leakage current density and the dielectric loss (tan ?) for BLFVx ceramics decreased gradually, while the dielectric constant (?r) first increased and then decreased gradually in this process, reaching a maximum value of 273 for x = 0.03. Among the BLFVx ceramics, the BLFVx=0.01 ceramic showed a well-saturated hysteresis loop with large remanent polarization (Pr) of 39.4??C?cm?2 and a low coercive electric field (Ec) of ?43.1?kV?cm?1 under an applied electric field of ?75?kV?cm?1. In addition, these ceramics exhibited good anti-fatigue characteristics after 2 ? 1010 read/write polarization cycles. These suggested that La3+ and V5+ co-doping was beneficial for enhancing the dielectric, ferroelectric and anti-fatigue properties of the BLFVx ceramics.

Effect of precursor solution concentration on the grain orientation of Bi3.15Nd0.85Ti3O12 thin films

Polycrystalline Bi3.15Nd0.85Ti3O12 (BNT) thin films were fabricated on Pt/Ti/SiO2/Si by the sol–gel method. The dependence of precursor solution concentration (PSC) on the grain orientation of the films was observed, and a model was proposed to explain it by taking into account the effect of bulk nucleation. With increasing PSC, the BNT thin film turned from c-axis-preferential-oriented to random-oriented. It is suggested that a competition exists between the nucleation and grain growth on the grain orientation. When the PSC is low, the former plays a predominant role, while in the opposite case, the latter is dominant. The bulk nucleation inhibits the homoepitaxial grain growth, and it gradually replaces the heterogeneous nucleation as the main nucleation mechanism with the increase in PSC.

The use of electron backscatter diffraction to measure the elastic strain fields in a misfit dislocation-free InGaAsP/InP heterostructure

Elastic strain fields at the interface of the epilayer and buffer layer of the InGaAsP/InP heterostructure were characterized by electron backscatter diffraction (EBSD) technology based on scanning electron microscopy. The InGaAsP/InP heterostructure which contained lattice misfit was under a dislocation-free condition. Image quality (IQ) was used as the strain sensitive parameter. From the image quality map and image quality curve, we observed directly the distribution of the elastic strain fields at the interface along the direction perpendicular to the interface as well as the interface structure between the epilayer and buffer layer by transmission electron microscopy and high resolution transmission microscopy.