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A general and facile ultrasonic irradiation method has been established for the synthesis of the lanthanide orthovanadate LnVO4(Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) nanoparticles from an aqueous solution of Ln(NO3)3and NH4VO3without any surfactant or template. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), and photoluminescence (PL) spectra as well as kinetic decays were employed to characterize the as-prepared products. Ultrasonic irradiation has a strong effect on the morphology of the LnVO4nanoparticles. The SEM and TEM images illustrate that the as-formed LnVO4particles have a spindle-like shape with an equatorial diameter of 30−70 nm and a length of 100−200 nm, which are the aggregates of even smaller nanoparticles of 10−20 nm. The results of XRD confirm the formation of a well-crystallized LnVO4phase with a tetragonal zircon structure. Eu3+and Dy3+doped zircon type LnVO4(Ln = La, Gd, Lu) samples show the characteristic dominant emissions of Eu3+at 613 nm (5D0-7F2) and Dy3+at 572 nm (4F9/2-6H13/2), respectively, as a result of an energy transfer from the VO43−to Eu3+(Dy3+). The formation mechanism of the spindle-like LnVO4nanoparticles with ultrasonic irradiation is discussed in the context. [ABSTRACT FROM AUTHOR]

Lu3Ga5O12Eu3+, Lu3Ga5O12Tb3+, and Lu3Ga5O12Pr3+, phosphors were prepared through a Pechini-type sol-gel process. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), photoluminescence, and cathodoluminescence spectra were utilized to characterize the synthesized phosphors. The XRD results reveal that the sample begins to crystallize at 800°C and fully crystallined pure Lu3Ga5O12 phase can be obtained at 1000°C. The FESEM image indicates that the phosphor sample is composed of aggregated rice grainlike particles with sizes around 80-120 nm. Under the excitation of ultraviolet light (250-275 nm) and low-voltage electron beams (1-3 kV), the Lu3Ga5O12Eu3+, Lu3Ga5O12Tb3+, and Lu3Ga5O12Pr3+ phosphors show the characteristic emissions Eu3+ (5D0 → 7F4,3,2,1 transitions, orange-red), Tb3+ (5D4 → 7F6,5,4,3 transitions, green), and Pr3+ (³P0 → ³H4, ³P1 → ³H5, ³P0 → ³H5, and ¹D2 → ³H4 transitions, green), respectively. The corresponding luminescence mechanisms are discussed. These phosphors have potential applications in area of field emission displays. [ABSTRACT FROM AUTHOR]

Trivalent dysprosium (Dy3+)-activated β-gallium oxide (β-Ga2O3) phosphors were synthesized by solid-state (SS), coprecipitation (CP), and citrate gel (CG) methods, respectively. The resulting β-Ga2O3:Dy3+F phosphors were well characterized by X-ray diffraction, field-emission scanning electron microscopy (FESEM), and by photoluminescence and cathodoluminescence spectra. The phosphors prepared by different methods show different luminescence properties under the excitation of UV and low-voltage cathode rays. There exists an energy transfer from the β-Ga2O3 host lattices to Dy3+, and the energy transfer efficiency was higher in the CG-derived phosphors than those of the SS- and CP-derived phosphors. Factors influencing the intensity of luminescence and the energy transfer efficiency from β-Ga2O3 host to Dy3+ in β-Ga2O3:Dy3+ phosphors were investigated in detail. It is shown that the CG method is the most respected process for the preparation of β-Ga2O3:Dy3+ phosphors. [ABSTRACT FROM AUTHOR]