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

Abstract

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 (τrad), 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.