Photoluminescence properties of Ca 2 Al 2 O 5 :RE 3+ (RE = Eu, Dy and Tb) phosphors for solid state lighting

Structural, morphological, and photoluminescence properties of RE (RE = Dy3+ , Eu3+ , Sm3+ )-doped CaAlBO4 phosphor synthesized by combustion method

The CaAlBO4 :RE (RE = Dy3+ , Eu3+ , Sm3+ ) phosphor were prepared via combustion synthesis and studied by X-ray diffraction (XRD), Fourier-transform infrared (FTIR) analysis, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), photoluminescence (PL) spectra and CIE coordinates. The phase formation of the obtained phosphor was analyzed by XRD and the result was confirmed by standard PDF Card No. 1539083. XRD data successfully indicated pure phase of CaAlBO4 phosphor. The crystal structure of CaAlBO4 phosphor is orthorhombic with space group Ccc2 (37). The SEM image of CaAlBO4 phosphor reveals an agglomerated morphology and non-uniform particle size. The EDS image provides evidence of the elements present and the chemical makeup of the materials. Under the 350 nm excitation, the emission spectrum of Dy3+ activated CaAlBO4 phosphor consists of two main groups of characteristic peaks located at 484 and 577 nm which are ascribed to 4 F9/2  → 6 H15/2 and 4 F9/2  → 6 H13/2 transition of Dy3+ respectively. The PL emission spectra of CaAlBO4 :Eu3+ phosphor shows characteristics bands observed around 591 and 613 nm, which corresponds to 5 D0  → 7 F1 and 5 D0  → 7 F2 transition of Eu3+ respectively, upon 395 nm excitation wavelength. The emission spectra of Sm3+ activated CaAlBO4 phosphor shows three characteristic bands observed at 565, 601 and 648 nm which emits yellow, orange and red color. The prominent emission peak at the wavelength 601 nm, which is attributed to 4 G5/2  → 6 H7/2 transition, displays an orange emission. The CIE color coordinates of CaAlBO4 :RE (RE = Dy3+ , Eu3+ , Sm3+ ) phosphor are calculated to be (0.631, 0.368), (0.674, 0.325) and (0.073, 0.185). As per the obtained results, CaAlBO4 :RE (RE = Dy3+ , Eu3+ , Sm3+ ) phosphor may be applicable in eco-friendly lightning technology.

Synthesis and photoluminescence properties of Eu3+ -activated Ba2 Mg(PO4 )2 phosphor

In this paper, we have reported the photoluminescence (PL) properties of the Ba₂ Mg(PO₄ )₂ :Eu³⁺ phosphor synthesized using a wet chemical method. The preliminary scanning electron microscopy (SEM) investigation of the sample revealed irregular surface morphology with particle sizes in the 10-50 μm range. The strongest PL excitation peak was observed at 396 nm. The emission spectra indicated that this phosphor can be effectively excited by the 396 nm wavelength. Upon 396 nm excitation, the emission spectrum showed characteristics peaks located at 592 nm and 615 nm. These intense orange-red emission peaks were obtained due to f→f transitions of Eu³⁺ ions. The emission peak at 592 nm is referred to as the magnetic dipole ⁵ D₀ →⁷ F₁ transition and the emission peak at 615 nm corresponded to the electric dipole ⁵ D₀ →⁷ F₂ transition of Eu³⁺ . The Commission Internationale de l'Eclairage (CIE) coordinates of the Ba₂ Mg(PO₄ )₂ :Eu³⁺ phosphor were found to be (0.586, 0.412) for wavelength 592 nm and (0.680, 0.319) for wavelength 615 nm situated at the edge of the CIE diagram, indicating high colour purity of phosphors. Due to the high emission intensity and a good excitation profile, Eu³⁺ -doped Ba₂ Mg(PO₄ )₂ phosphor may be a promising orange-red phosphor candidate for solid-state lighting applications.

Site preference for luminescent activator ions in doped fluoroperovskite RbZnF3

With the dual objective of investigating the site preferences of larger sized activator ions and to append luminescence property to the perovskite structured RbZnF₃, doping of manganese(II), cerium(III), europium(III) and terbium(III) ions (5 mol%) was carried out. Although cubic symmetry of RbZnF₃ was preserved for all the doped samples, site preference of rare-earth ions for the A-site Rb⁺ leading to an inverse perovskite arrangement has been noticed from careful analysis of lattice parameters from refinement of powder X-ray diffraction data. Undoped RbZnF₃ exhibited rod-like morphology in the transmission electron microscopic image. In addition to an intense band around 230 nm assignable to the charge transfer from ZnF₃^- to Rb⁺, typical transitions of respective dopant ions were observed in their UV-visible spectra. The doped samples showed luminescence in blue, green and red regions and time decay experiments suggested uniform dispersion of them without any clustering effect. The lower phonon energy of RbZnF₃ matrix by virtue of the presence of heavier rubidium at the A-site together with its doping with rare-earth ions resulting in an inverse perovskite like arrangement could favour their utility in various practical applications.