Mechanism of Luminescence Enhancement in Eu3+ Activated Double Perovskite Phosphors Bi2-xEuxWO6 (x = 0-0.24) Prepared by Sol-Gel Method

Abstract

A double perovskite structured series Bi_2–xEu_xWO₆ (x = 0.03-0.24) was prepared by using simple citrate sol-gel method at 700 ºC for 5 h of sintering. The double perovskite structure and its lattice parameters were analyzed by the XRD technique and found to be pure orthorhombic phase. The concentrated sample of x = 0.12 exhibits more intensity than all other concentration in their emission spectra. Particle size, thickness of the particle, distance between particles and its surface morphology were identified by scanning electron microscopy. The size and distance between particles lies in between the range of 1-50 nm and 20-50 nm, respectively. In addition to this the absorption of light capacity for every sample was investigated through diffuse reflectance spectra method. All the samples of double perovskite structures exhibit a sharp cut-off of absorption light in the UV and visible regions of diffuse reflectance spectra. Predominantly, sample x = 0.12 shows very good charge transfer band in their excitation spectra that leads to more absorption of light correspondingly emits high intensity in emission spectra. All the samples of series emit main peaks in the range of 550-700 nm in their emission spectra. Out of all four main peaks, 614 nm peak represents the red phosphor with ⁵D₀−⁷F₂ transition in the emission spectra. The prepared double perovskite structure compound CRI co-ordinates (0.6254, 0. 3739) are almost close to commercially available red phosphor i.e. Y₂O₂S (0.67, 0.33) as per NTSC. Hence, the prepared red phosphors can be used in order to display devices, luminescent materials and WLEDs.