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A series of blue-emitting NaCaBeSi2O6F:Eu2+ phosphors were obtained via a solid state reaction. NaCaBeSi2O6F:Eu2+ exhibit a broad absorption from 250 to 450 nm when monitored at 467 nm and display a broad emission band from 400 to 600 nm when excited at 397 nm. The concentration quenching was obtained when the concentration of Eu2+ was increased to 0.8 mol%. Energy transfer interactions between Eu2+ in host is due to dipole-dipole mechanisms and the critical distance was calculated to be 31.96 A. The results obtained in this study highly indicates that NaCaBeSi2O6F:Eu2+ can be a potential blue-emitting phosphor for light quality improvement in white-LED applications.

A novel green-emitting phosphor – K 2 Ba 5 Si 12 O 30 :Eu 2+ (KBSO:Eu 2+ ) was successfully synthesized via a solid state reaction. The crystal structure, luminescent properties as well as thermal quenching and LED fabrication were systematically carried out in this study. The emission and excitation spectra indicate that KBSO:Eu 2+ phosphors exhibit broad excitation spectra ranging from 260 to 480 nm and an intense broad green emission at 497 nm under 370 nm excitation. The chromaticity coordinates of composition-optimized KBSO:Eu 2+ phosphor is situated in the green region with coordinates (0.2404, 0.4429). The temperature-dependent photoluminescence demonstrates that KBSO:Eu 2+ gives a good thermal quenching performance of ∼80% at 100 °C, which is much superior to that of commercial silicate-based phosphor of (Ba, Sr) 2 SiO 4 :Eu 2+ . Warm-white light-emitting diodes (LEDs) fabricated using an NUV-chip combined with the KBSO:3%Eu 2+ phosphor gave color rendering indices 82.65, correlated color temperatures 4939 K, and the CIE chromaticity coordinates 0.3064, 0.3325). These results indicate that KBSO:Eu 2+ is a potential green-emission phosphor for near UV and high powder white-light LEDs.

Novel silicate-based phosphors—NaCaGaSi2O7:RE, Li+ (RE = Ce3+, Eu3+ or Tb3+) was synthesized by a solid state reaction. The crystal structure, luminescence properties, as well as concentration quenching, thermal stability and CIE chromaticity coordinates were investigated. By introducing Ce3+, Eu3+ and Tb3+ into NaCaGaSi2O7, an intense blue emission at 388 nm, red emission at 613 nm and green emission at 541 nm could be generated in optimal excitation wavelengths of 332 nm, 393 nm and 377 nm, respectively. The optimized doping concentration and critical energy transfer distance of Ce3+, Eu3+ and Tb3+ in NaCaGaSi2O7 were determined to be 1, 10, 25 mol% and 30.61, 10.47 and 14.21 A, respectively. The CIE coordinates of NaCaGaSi2O7: 1% Ce3+, 1% Li+, NaCaGaSi2O7: 10% Eu3+, 10% Li+ and NaCaGaSi2O7: 25% Tb3+, 25% Li+ phosphors were (0.1602, 0.0192), (0.6470, 0.3493) and (0.3211, 0.4820), respectively. The results indicate that the as-synthesized NaCaGaSi2O7:RE, Li+ phosphors were potential candidates for UV-LEDs.

In this paper, the stepped reduction method is used to find general solutions for the nonaxisymmetric bending of arbitrary axisymmetric nonhomogeneous annular plates of variable thickness under an arbitrary nonaxisymmetric temperature field and an arbitrary nonaxisymmetric distributed load. In spite of a large number of steps, eventually only two simultaneous algebraic linear equations with two unknowns have to be solved. As an example, the bending of a circular plate, whose solution is known, is carried out by the proposed approach, and it is shown that results obtained by the proposed method compare well with previous solutions obtained by other methods and hence prove the accuracy of the proposed method.

The original contribution in the present paper can be described as: using the equilibrium equations of paraboloidal shallow shells expressed by displacements and by introducing a displacement function U , the general solution of the equation can be represented by U ( r , ϕ ), and the equations can be reduced to single eighth-order equation of U ( r , ϕ ). The displacement function introduced initially by the authors plays an important role as does Vlasov's displacement function for the cylindrical shell. The exact series form solution of the equation has been obtained for the bending problem of the shells. Numerical examples have been carried out for the shell with clamped boundary condition.

A new Eu2+-doped barium beryllium silicate, BaBeSiO4:xEu2+ (1% ≤ x ≤ 10%) phosphor was successfully synthesized by the high temperature solid-state reaction. The phosphor system was investigated as a novel candidate for phosphor-converted white light-emitting diode (LED) applications. The evolution of luminescence and structure of the phosphors induced by variation of sintering temperature are investigated using photoluminescence spectra and X-ray diffraction techniques. The concentration quenching and thermal quenching process of the phosphor were also investigated in detail. The BaBeSiO4:Eu2+ phosphor exhibits broad excitation spectra ranging from 250 to 400 nm, and a blue emission band centered at 460 nm under λex = 337 nm. The main parameters of the electron-vibrational interaction, such as Huang-Rhys factor, effective phonon energy, and zero-phonon line position, were all estimated. The optimal concentration of Eu2+ ions in BaBeSiO4 was determined to be 3 mol.%. The corresponding concentration quenching mechanism was verified to be the electric dipole−dipole interaction. The activation energy of BaBeSiO4:Eu2+ for thermal quenching was calculated to be 0.19 eV with the Arrhenius equation. The LED device exhibited an excellent color-rendering index Ra of 90.13 at a correlated color temperature of 4077 K with CIE color coordinates of (0.38, 0.39) under a 350 mA forward-bias current. Based on these results, we are currently evaluating the potential application of BaBeSiO4:Eu2+ as a white-emitting UV-convertible phosphor for high power LED applications.

A rotating disk with varying thickness and inhomogeneity, and subjected to a steady, inhomogeneous temperature field is analyzed. To handle the arbitrary profile, the disk is discretized into a series of uniform annular disks possessing constant material properties and then solved by the step-reduction method. Analytic expressions for thermoelastic stresses are given, and based on these results, the formulation is extended to include the calculation of shrink fit, the solving of the inverse problem for equistrength rotating disks, and the computations of plastic stresses and creep at elevated temperatures.