Search

The Dy3+ doped lithium sodium potassium borate glasses with white light-emitting were prepared by the melt quenching technique. In this work, optical, photoluminescence properties and Judd-Ofelt analysis of borate glasses have been investigated. For optical properties, Dy3+ doped glasses showed the absorption in visible and near-infrared region, which originate from 6H15/2 ground state to higher state. While the luminescence properties of Dy3+ doped glasses, the emission spectra were presented more intense at 484 nm (blue light) and 574 nm (yellow light) which are essential for white light emitting materials, whilst decay time decrease with an increase of Dy2O3 contents. The emission intensity of Dy3+ doped glasses were enhanced by adding Dy2O3 concentrations until 0.5 mol%, after that the emission intensities were decreased due to the concentration quenching effect. Judd-Ofelt is analyzed by using the absorption and photoluminescence results, The stimulated emission cross-section has been investigated in this work. The CIE 1931 chromaticity investigation shows that Dy3+ doped glass emitted light with white color. Hence, these glasses may be suitable candidates for use in W-LEDs material. [ABSTRACT FROM AUTHOR]

B2O3–Bi2O3–SiO2–Sm2O3 glasses have been synthesized by melt quench technique for different mol% Sm2O3. The electrical behavior of these glasses was studied by impedance spectroscopy technique at room temperature, covering the frequency range between 1 M and 1 GHz. In addition, dielectric measurements were made to evaluate the dependence of the dielectric constant different Sm ions. The dielectric constant is approximately 3200 at room temperature for 0.5 mol% Sm-doped compositions at 645 MHz frequency. The results show significant variations for the real part and large variations for the imaginary part among different frequency with different Sm fractions. Complex impedance analysis was used to estimate its electrical conductivity as well as its corresponding optical properties. [ABSTRACT FROM AUTHOR]

Phase formations and dielectric properties of lead free barium titanate bismuth zinc zirconate, BaTiO3-Bi(Zn0.5Zr0.5)O3 (BT-BZZ), were comparatively investigated between two different synthesis routes, solid state reaction and salt flux assistance methods. The perovskite (1-x)BT-(x)BZZ ceramics, where x = 0.02, 0.05 and 0.10, were synthesized by using reagent grade oxides and the NaCl salt was used as a surface active agent to lower the calcination temperature. Phase formations were examined by X-ray diffraction technique (XRD). It was found that the solid solutions of (1-x)BT-(x)BZZ can be obtained with lower temperature at least 200 °C via salt flux assistance method. The NaCl salt addition could result in single phase of perovskite structure at every compositions with the calcination temperature as low as 800 °C. Dielectric measurements revealed that the Curie temperature (Tc) shifted to lower temperature with increase of BZZ concentration. Moreover, the dielectric behavior transformed to diffuse phase transition when x = 0.1. The samples prepared via salt flux assistance method exhibited smaller grain size which were revealed by scanning electron microscope. In addition, P-E hysteresis measurements illustrated the higher high E-field dielectric constant with the narrower P-E loop when the salt flux was applied. [ABSTRACT FROM AUTHOR]

Ceramic systems of Ba1−xLaxTiO3 with La-doping contents of x = 0, 0.005, 0.01, 0.02, 0.04, and 0.08, denoted as BT, BLT0.5, BLT1, BLT2, BLT4, and BLT8, respectively, were synthesized by the solid-state reaction route. All systems were observed the crystal structure, dielectric constant ( ε r ), dielectric loss ( tan ⁡ δ ) , polarization and electric field-induced strain. Thermoelectric properties including electrical resistivity ( ρ), Seebeck coefficient (S), and power factor (PF) of all systems were also performed. The BT0.5 provided the best shot in a term of ferroelectric properties since lanthanum could well diffuse into the BT lattice and enhance the dielectric constant and polarization, while BT1 was quite good for thermoelectric aspect as ion displacement and electrical conductivity was well incorporated. The result suggests that the BT1 system has a possible potential to be further developed for high-temperature thermoelectric applications in the case of polycrystal ceramics. [ABSTRACT FROM AUTHOR]

Barium titanate (BaTiO3) has been recognized as an important perovskite ceramic since its discovery due to its excellent dielectric, ferroelectric and piezoelectric properties. Its modifications have been studied in many perspectives depending on applications. In this review, the basic principles of BaTiO3 were described, then followed by the explanation on the recent modifications of BaTiO3 to improve the dielectric properties. Relaxor ferroelectric behavior of BaTiO3 was revealed by combining BaTiO3 with other Bi-based perovskites. These modified- BaTiO3 opened the opportunities for emerging energy storage applications. Next, the modifications for ferroelectric and ferromagnetic aspects were further discussed. BaTiO3 can also be doped by other ions to enhance such properties. Solid solution between Bi-based perovskites such as BiFeO3, (Bi0.5K0.5)TiO3, or Bi(Zn0.5Ti0.5)O3 and BaTiO3 can also improve ferroelectric and ferromagnetic properties. Therefore, these details of recent BaTiO3 modifications may provide guidance for the next BaTiO3 investigations in order to gain the maximum benefits from BaTiO3. [ABSTRACT FROM AUTHOR]

The gadolinium tungsten calcium silicon borate glasses doped with Tb3+ were prepared using the melt quenching technique to study physical, absorption and luminescence properties. The results show that doping with Tb2O3 in high concentration makes the glass density tendency to increase. The absorption spectra indicate the photon absorption of Tb3+ in the visible and near infrared ranges. The emission spectra of these glasses have been recorded under 275 nm (Gd3+) and 377 nm (Tb3+) excitation wavelengths, and it is has been observed that these glasses show bright green emission. From the emission spectra, Tb3+ doped glasses perform the strongest emission with the wavelength 544 nm. The optimum concentration of Tb3+ with the strongest emission in Gd2O3--WO3--CaO--SiO2--B2O3 is 1.50 mol.%. CIE 1931 chromaticity investigation shows that Tb3+ doped glasses emit the light with yellowish green color. Tb3+-doped glasses have the interesting potential to further development for using as laser medium in yellowish green solid-state lasers. [ABSTRACT FROM AUTHOR]

Impedance spectroscopy was used in order to investigate the electric properties of double perovskites of the Y2NiMnO6 ceramics, which were prepared by thermal decomposition at 800 °C for 6 h followed by sintering at 1400 °C for 6, 12, 18 and 24 h. Consequently, the electric characterization of the Y2NiMnO6 ceramics was performed at temperature from °50 to 200 °C, in the frequency range from 10² to 108 Hz. Results in the activation energy relaxation (Ea(τg))are significantly increased from 0.1723 to 0.3813 eV and the conductivity activation energy (Eaσgb) in the grain boundary are dramatically increased from approximately 0.3599 to 0.6260 eV at 24 h. Dispersion was observed in the variation of impedance values with frequency. Possible reasons for these observations are discussed. [ABSTRACT FROM AUTHOR]