Hydrothermal synthesis and dielectric properties of lanthanum titanate ceramics

Lanthanum titanate （La2/3 TiO3） powders were synthesized by hydrothermal method based on the reaction of TiO2, La（NO3）3 and KOH at 160℃ for 24 h followed by the treatment of acidification. The microstructure, morphology and dielectric properties were investigated by using X-ray diffraction, scanning electron microscope, transmission electron microscope and impedance method. The results show that the La2/3TiO3 particles consist of nearly homogenous and lamellar grains. The particles can be sintered into porous ceramics above 1150℃. The dielectric properties of La2/3 TiO3 show that both the dielectric constant and the dielectric loss tangent decrease with the increase of frequency.

Josephson effect in the strontium titanate/lanthanum aluminate junction

We report theoretical studies on the newly discovered novel Josephson effect and scanning tunneling spectroscopy(STS) at the interface of strontium titanate/lanthanum aluminate(STO/LAO).With a phenomenological boson-fermion model, the density of states is calculated and the results are consistent with the STS experiments.A typical calculation of Josephson effect is performed, and it is in qualitative agreement with the experiments.The calculations indicate that the gap states come from the pairing of quasi-particles with a finite total momentum and the Josephson current comes from the tunneling of quasi-particle pairs with zero momentum.The quasi-particles are Bogoliubov quasi-particles.Moreover, the fits using Kulik's formula imply that the Josephson junction at the STO/LAO interface has a point contact with the clean superconductor limit.

Rapid Synthesis and FT-Raman Spectroscopic Study of Lanthanum Modified Lead Titanate Nanocrystals

Pb_ 1-xLa_xTi_ 1-x/4O_3 nanocrystals with different amounts of lanthanum were prepared by modified sol-gel method and detected by FT-Raman spectra at 288 and 378 K, respectively. The improved synthetic technique used in this paper could obtain nanocrystals with apparently promoted synthetic speed from a few days to several hours (4 times faster of hydrolytic process than that of traditional sol-gel method and reduced preparation period of gel from 24 h to several hours) at relatively lower temperature by hydrolysis of sol to gel through adding methyl alcohol/water solution into sol under vigorous stirring and annealed the fresh gel directly. The effects of lanthanum′s amount, annealed temperature and nanocrystals′ grain size of Pb_ 0.9La_ 0.1Ti_ 0.975O_3 nanocrystals on frequency, shape and width of the phonon peak were also discussed in detail.

Sol-gel synthesis and photoluminescence characterization of La_2Ti_2O_7:Eu^(3+) nanocrystals

Eu3＋ doped La2Ti2O7 nanocrystals with pure monoclinic phase and size of about 100 nm were prepared by a citric acid （CA） assisted sol-gel method. Techniques of thermo-gravimetric （TG） and differential scanning calorimetry （DSC）, X-ray diffraction （XRD）, as well as transmission electron microscopy （TEM） were employed to characterize the as-synthesized nanoparticles. Furthermore, photoluminescence （PL） performances of the Eu3＋ doped La2Ti2O7 nanocrystals were evaluated with focus on the effects of calcination temperature and Eu3＋ doping concentration on the photoluminescence properties.

Synthesis and Property of H_2La_2Ti_3O_(10)/CdS Layered Nanocomposite Photocatalyst

H2La2Ti3O10/CdS nanocomposite with er photoactivity was synthesized by a stepwise exchange process from H2La2Ti3O10, which was obtained by H^＋ -exchanging reaction of H2La2Ti3O10 with HCl other than the normally used HNO3. The pillaring process was investigated by XRD, TEM, FT-IR and BET methods. The photocatalytic decomposition of aniline was used as the model system to evaluate the photochemical properties of H2La2Ti3O10/CdS,H2La2Ti3O10 and K2La2Ti3O10. It is found that the photoactivity of layered H2La2Ti3O10 is greatly improved by the intercalation of CdS in the interlayer. In general, the excellent photoactivity of the H2La2Ti3O10/CdS nanocomposite might be attributing to the extremely small particle size of incorporated CdS and good contact between CdS and La2Ti3O10^2- layers. On the other hand, the coupling of two semiconductor particles with different energy gap is useful to achieve effective charge separation. In H2La2Ti3O10/CdS, a photo-generated electron can transfer from CdS to the La2Ti3O10^2- layer, while the holes remain in the CdS particles. This helps to diffuse the electrons and holes before reaching the interface, and the holes and electrons can be effectively captured by the electrolyte in the solution. Simuhaneously, the optimal operating condition of photodecomposition aniline was investigated.

Synthesis of Ultrafine K_2Ln_2Ti_3O_(10) by Microemulsion Method and Its Photoactivity Research

A series of uhrafine K2Ln2Ti3O10（Ln = La, Ce, Pr, Nd, Sm, Eu, Dy）photocatalyst was prepared by microemulsion method based on tetrabutyl titanate reacting with potassium hydroxide and lanthanumoxide. The obtained products were characterized by XRD, TEM and UV-Vis spectra. These results indieate that highly ultrafine K2Ln2Ti3O10 can be accessible at lower fabricating temperature and shorter reation time by this approach. In addition, the investigation on their eatalytieal behavior based on the degradation of methyl orange under UV-Vis light suggests that the degradation rate can reach up to 60%.