The orange red luminescence and conductivity response of Eu3+ doped GdOF phosphor: Synthesis, characterization and their Judd-Ofelt analysis

Present paper reports the synthesis of a series of Gd1-xEuxOF (0.01� x � 0.09) phosphor by solid state route at low temperature. Characterizations such as powder x-ray diffraction (PXRD), Rietveld refinement, scanning electron microscopy, UV-Visible absorption, AC conductivity and photoluminescence (PL) spectroscopy were carried out. Rietveld refinement of powder XRD data confirms the crystallization of the compounds in rhombohedral structure. Investigation of PL under 395 and 465 nm excitation wavelengths is done. Upon substitution Gd3+ by Eu3+ ions in GdOF, the PL spectra exhibited emission at 5D0 � 7F0 (579 nm), 5D0 � 7F1 (593 nm), 5D0 � 7F2 (612, 620 nm), 5D0 � 7F3 (651 nm) and 5D0 � 7F4 (705 nm) transitions. JO theory parameterization variation from emission spectra is used to compute the intensity parameters (Ω2, Ω4) of phosphors. Using the intensity parameters the radiative lifetime (�rad), radiative transition probabilities (AT), branching ratio (β) are evaluated. Dielectric and AC conductivity of Gd1�xEuxOF (0.01 � x � 0.09) is studied in the frequency range from 100 Hz to 5 MHz at a temperature of 300 K. Studies reveal that the AC conductivity increases gradually beyond 30 kHz up to100 kHz and rapidly increases at 300 kHz. At lower frequencies, it is found that the compound exhibit high values of dielectric loss and dielectric constant, which decreased drastically with increasing frequency. The result so obtained reveals that present phosphors could be a possible source for orange red constituent in white LEDs and is best suited for microwave device applications because of its low values of dielectric loss

Effect of Li, Na, K cations on photoluminescence of GdAlO3:Eu3+ nanophosphor and study of Li cation on its antimicrobial activity

Alkali metal cations such as Li, Na, K (1mol %) co-doped GdAlO3:Eu3+ (1 mol%) nanophosphors were synthesized by solution combustion technique using oxalyldihydrazide (ODH: C2H6N4O2) as fuel. The structural, morphological, luminescence and antimicrobial activity has been employed to the synthesized nanoparticles. All compounds crystallized in the pure orthorhombic phase with no impurity peak. SEM micrographs showed the agglomerated and irregular shaped particles. The average crystallite size was calculated by William-Hall plots and is found to be in the range 30-40 nm. The characteristic emission peaks of Eu3+ ions were recorded and it is due to D-5(0)-> F-7(J) (J = 1, 2, 3, 4) transitions. The PL intensity of GdAlO3:Eu(3+)nano phosphor was improved evidently by alkali metal cation co-doping, due to local distortion of crystal field surrounding the Eu3+ activator. These nanophosphors find potential applications in WLEDs and solid state lighting. Antimicrobial activity of GdAlO3:Eu3+:Li+ nanophosphor against pathogenic microorganisms of both human and plants was carried out by using micro plate dilution technique for bacteria and food poison method for fungi. (C) 2017 Elsevier B.V. All rights reserved