Papers by Author: Dan Xie

Abstract: Multifunctional BiFeO3 (BFO) thin films were deposited on Bi3.15Nd0.85Ti3O12 (BNdT)/Pt and Pb(Zr1−x,Tix)O3 (PZT)/Pt substrates respectively by sol-gel process. The ferroelectric properties were studied for Metal-Ferroelectric-Mental (MFM) capacitors. The MFM structure exhibited well clockwise capacitance-voltage hysteresis loops due to the ferroelectric polarization of multilayer thin films achieved. The remnant polarization (2Pr) of the BFO/PZT and BFO/PZT multilayer capacitors were 45.1μC/cm2 and 23.2μC/cm2, respectively at the applied voltage of 8V. The leakage current of Pt/BFO/BNdT/Pt is about 3×10-5A/㎝2 at applied voltage of 4V, one order smaller than Pt/BFO/PZT/Pt capacitor. For the BFO/BNdT/Pt, it exhibited a weak saturated ferromagnetic response at room temperature and the multilayer was anti-ferromagnetic. However, for the BFO/PZT/Pt, well-developed M-H loops together with remnant magnetizations can be observed in at room temperature. The highest saturation magnetizations (Ms) of both capacitors were measured to be 2.47emu/cm3.

Abstract: {0.75SrBi2Ta2O9-0.25Bi3TiTaO9}(SBT-BTT) thin films were prepared by the modified metalorganic solution deposition (MOSD) technique. The microstructure and ferroelectric properties of SBTBTT thin films were studied. The SBT-BTT thin films were produced at 750°C. The grain size and surface roughness of SBT-BTT films showed significant enhancement with an increase in annealing temperatures. It is found that SBT-BTT thin films have good ferroelectric properties. The measured remanent polarization values for SBT-BTT, SBT and BTT capacitors were 15, 7.5 and 4.8μC/cm2, respectively. The coercive field for SBT-BTT capacitors was 50kV/cm. More importantly, the polarization of SBT-BTT capacitors only decreased 5% after 1011 switching cycles at a frequency of 1MHz.

Abstract: Ni-Si-O thin films on Si substrate have been prepared by a sol-gel method. The microstructure and phase composition of the films were investigated by XRD, SEM, FTIR. The XRD results showed that the films are amorphous while annealed at 800oC for 10 min, the SEM imagines proved that the films are smooth and thickness is about 190 nm. Electrical property of the film indicated that the leakage current was as low as 10-6A/cm2 at an electric field of 1MV/cm. The dielectric properties of Ni-Si-O thin films can be improved as increasing the annealed temperature.

Abstract: The uniform Sr0.5Ba0.5Bi4Ti4O15 thin films were prepared using a modified Sol-Gel technique and the influence of precursor on the microstructure and characterization of thin films were studied. The stability and uniformity of precursor solution is key issue for the quality of thin films. Ethanolamine is an effective complexation reagent of Bi3+, which could moderate the acidity of precursor. When pH value and concentration of precursor solution was about 3.5 and 0.35M respectively, the smooth and uniform Sr0.5Ba0.5Bi4Ti4O15 thin films could be obtained. The Bi-layered perovskite structure of Sr0.5Ba0.5Bi4Ti4O15 formed at 750°C. The morphology of the grains in Sr0.5Ba0.5Bi4Ti4O15 thin films was elliptoid and the grain size was about 90 ~ 100 nm.

Abstract: The preparation and the microstructure of BaBi4Ti4O15 (BBT) thin films were reported in the paper. BBT thin films were fabricated on silicon substrate using a modified Sol-Gel technique. A key issue of Sol-Gel processing is the chemical reaction and mechanism of precursor solution, which governs the crystallization and characteristics of the final oxide layer. Ethanolamine is an effective complexation reagent of Bi3+, which could moderate the acidity of precursor. When pH value is about 3.5, the stable and uniform BBT precursor solution could be obtained. The Bi-layered perovskite structure of BBT forms at 750°C. The morphology of the grains in BBT thin films is spheroidal and the grain size is about 120nm.

Abstract: Bismuth sodium titanate ceramic was prepared by sol-gel method. The crystallization, density and microstructure were determined. The grains of BNT ceramic prepared by sol-gel method were equiaxial, ~ 2 µm, which was smaller than that prepared by solid-state reaction method. The piezoelectric and dielectric properties were investigated. When the sintering temperature was 1140°C, maximum relative dielectric constant and piezoelectric constant can be obtained. The piezoelectric constant of BNT ceramic prepared by sol-gel method was higher than those prepared by solid-state reaction method.

Abstract: In the paper, the microstructure and properties of Sr1-xBaxBi4Ti4O15 (SBBT) ceramics with different Ba contents were investigated. SBBT ceramics were fabricated by means of the method combining Sol-Gel process and ordinary firing. The morphology will change when Ba2+ is doped in SrBi4Ti4O15 (SBTi), which will lead to the change of structure and ferroelectric properties. The microstructure of SBTi and BaBi4Ti4O15 (BBTi) ceramics were characterized by scan electron microscopy (SEM). With the increase of Ba2+ doping contents, the sintering temperature of SBBT ceramics decreases, 1120°C for SBTi and 1060°C for BBTi. BBTi ceramics contain more and larger plate-like grains than that in SBTi, the diameter of the grains in BBTi is about 8~10 µm, the thickness is about 2.5 µm. With the increase of Ba2+ doping contents, remanent polarization (Pr) and coercive electric-field (Ec) increase first and then decrease. At the molar ratio of Sr:Ba=0.5:0.5, SBBT ceramics exhibited the highest Pr and Ec.