Local Structure and Spectroscopic Properties of Eu³⁺-Doped BaZrO₃

Abstract

Pristine and Eu3+-doped BaZrO3 were synthesized via a solid-state reaction method, and the synthesized samples were systematically characterized. X-ray diffraction confirmed the formation of single and pure phases of cubic-structured BaZrO3. Extended X-ray absorption fine structure (EXAFS) spectroscopy revealed the site occupancy of Eu3+ and coordination environment around the different atomic sites. Photoluminescence (PL) excitation and emission spectra revealed the dominant absorption at 275 nm and a broad emission centered at 400 nm due to oxygen vacancies below the conduction band (CB). The PL emission intensity at 597 nm increased with increasing Eu3+ doping concentration; simultaneously, emission from the defect level decreased. This confirmed the efficient energy transfer from oxygen vacancies to Eu3+. Density functional theory was employed to calculate the density of states (DOS) to explain the mechanisms of the PL phenomenon. DOS also showed the presence of impurity states due to Eu3+ doping within the band-gap region. The coincidence of the oxygen vacancy state with Eu f state at the bottom of the CB confirmed the PL energy-transfer mechanisms from the oxygen vacancy to europium. The excited-state lifetime values of the 5D0 state decreased with increasing doping concentration due to the increase of the nonradiative transition rate. The internal quantum efficiency, small excited-state lifetime, and photometric parameters indicated that 3 mol % Eu3+-doped BaZrO3 can be a suitable candidate for the red-light-emitting device applications.

Dependence of Luminous Performance on Eu3+ Site Occupation in SrIn2(P2O7)2: The Effect of the Local Environment

“…According to eq , the calculated values of Ω 2 and Ω 4 for S 0.9 IP: Eu 0.1 are 3.73 × 10 –20 and 2.06 × 10 –20 cm 2 , and the values of Ω 2 and Ω 4 for SI 1.92 P: Eu 0.08 are 3.92 × 10 –20 and 2.16 × 10 –20 cm 2 , respectively. As a general rule, Ω 2 is particularly influenced by the local crystal environment of the luminescence center, which can be used as an index to judge the asymmetry of Eu 3+ , while the crystal environment hardly affects Ω 4 , which generally reflects the overall property and rigidity of the host lattice . Herein, the J–O intensity parameter factor Ω 2 of both S 0.9 IP: Eu 0.1 and SI 1.92 P: Eu 0.08 is much higher than the corresponding Ω 4 , which proved the low symmetry nature of the Sr and In sites occupied by Eu 3+ .…”

Site-Selective Eu3+ Doping and Enhanced Luminescence from Eu3+ at B Sites in Perovskite-Type Strontium Zirconate and Hafnate

“…However, two different spectral shapes of photoluminescence (PL) were obtained probably because the charge compensation by La 3+ and B-site doping of Eu 3+ were not satisfactory. Similar difficulties in the site-selective doping of Eu 3+ were also reported in BaHfO 3 . , Therefore, the actual occupation sites of Eu 3+ ions and the accurate PL properties and efficiencies have not been understood sufficiently. − Because Eu 3+ ions are often incorporated at either A or B sites unintentionally in the perovskite-type zirconates, − highly controlled site-selective doping of Eu 3+ is essential to obtain the expected high luminescence efficiency.…”

KNN–Eu transparent ferroelectrics: Local structure and luminescent property

“…All the samples display two yellow emissions, two orange emissions, and a strong red emission in the visible range, corresponding to the 5 D 0 → 7 F 0 (578 nm), 5 D 0 → 7 F 1 (591 nm), 5 D 0 → 7 F 2 (614 nm), 5 D 0 → 7 F 3 (650 nm), and 5 D 0 → 7 F 4 (700 nm) transitions of Eu 3+ ions, respectively 40,41 . Among these spectral emission bands, all the samples show the sharpest emission peak located at 700 nm due to the electric dipole transition 5 D 0 → 7 F 4 , much higher than the 5 D 0 → 7 F 0 and 5 D 0 → 7 F 1 transition that belong to magnetic dipole transition 42 . It is known that the intensities of the electric dipole transition and the magnetic dipole transition depend on the local symmetry of the Eu 3+ ions location 43 .…”

“…40,41 Among these spectral emission bands, all the samples show the sharpest emission peak located at 700 nm due to the electric dipole transition 5 D 0 → 7 F 4 , much higher than the 5 D 0 → 7 F 0 and 5 D 0 → 7 F 1 transition that belong to magnetic dipole transition. 42 It is known that the intensities of the electric dipole transition and the magnetic dipole transition depend on the local symmetry of the Eu 3+ ions location. 43 The A-site that Eu 3+ ions occupied in the KNN matrix without inversion symmetry and result in the dominant of electric dipole transition.…”