Structures and luminescence properties of Yb ³ + in the double perovskites Ba ₂ Y B ′O ₆ ( B ′=Ta ⁵⁺ , Nb ⁵⁺ ) phosphors

Abstract

The Yb3+ doped Ba2YB′O6 (B′=Ta5+, Nb5+) were prepared by high temperature solid-state reaction method, their structures were determined by x-ray diffraction and refined by Rietveld method. The diffuse reflection absorption, excitation and emission spectra of Yb3+:Ba2YB′O6 (B′=Ta5+, Nb5+) were measured at room temperature. Under the excitation of ultraviolet light, these phosphors exhibit broad charge transfer band emissions of TaO6 or NbO6 centre with large Stokes shift. The Yb3+ doped into these hosts are situated at Y3+ sites of cubic symmetry (Oh). The experimental energy levels of Yb3+ in Ba2YTaO6 and Ba2YNbO6 were determined by photoluminescence and diffuse reflection absorption spectra. Their wavefunctions and theoretical energy levels were obtained by diagonalising the Hamiltonian matrix. The experimental energy levels were fitted by Levenberg—Marquardt iteration algorithm to determine crystal field parameters. Then, the magnetic-pole transition line strengths of Yb3+:Ba2YB′O6 (B′=Ta5+, Nb5+) from (2F5/2)Γ−8 to the low-energy states were calculated.

Double Perovskite Structure: A Vibrational and Luminescence Investigation Providing a Perspective on Crystal Field Strength

“…The spectral resolution is not adequate for band assignments of crystal field levels. The emission spectra (Figure b) exhibit maximum intensity at ∼595 nm and differ considerably from those reported by Xiao and Yan but are consistent with the emission spectrum of Blasse et al and Yu et al The room temperature charge transfer excitation and emission bands of Ba 2 YNbO 6 and Ba 2 YTaO 6 have been reported at 314, 263 nm (excitation) and 530, 390 nm (emission), respectively . The maxima in the room temperature excitation spectra (Figure a) are at 262 nm and 277, 305 nm, respectively for Ta–O and Nb–O charge transfer bands, but the corresponding emission bands are almost quenched via energy transfer to Eu 3+ .…”

“…This value is in fact the calculated energy difference between the 7 F 0 and 7 F 1 multiplet states and in the absence of J -mixing would be equal to ζ(4f)/6. Zhou et al have investigated the luminescence of Ba 2 YMO 6 (M = Nb, Ta) doped with Yb 3+ at room temperature. The spectra were assigned to Yb 3+ at an octahedral site in this host.…”

“…Nanorods of Ba 2 YNbO 6 have been embedded in YBa 2 Cu 3 O 7 films in order to improve flux pinning in magnetic fields . Other applications include a lead-free ultrasonic transducer for microelectronics, solid oxide fuel cells, and microwave tunable systems. − The band gaps of Ba 2 YTaO 6 and Ba 2 YNbO 6 are 4.6 and 3.8 eV, respectively . The valence band is mainly composed of O(2p) orbitals, whereas the conduction band arises from the interaction between oxygen and transition metal t 2g orbitals for which the overlap increases when replacing a 4d ion with a more electropositive 5d ion …”

Electronegativity, Charge Transfer, Crystal Field Strength, and the Point Charge Model Revisited

“…Plot of N v against number of 4f electrons of Ln 3+ in (a) LnCl 6 3– (data from ref ) and (b) LnO 6 9– (data from refs , , and . In ref , the multiplicative factors arising from the reduced matrix elements were omitted from the values of crystal field parameters.…”

Density-functional theory investigation of electronic structure, elastic properties, optical properties, and lattice dynamics of Ba2ZnWO6

“…Due to their uncommon properties and potential applications, double perovskite A 2 BCO 6 compounds have been investigated extensively. [1][2][3][4][5][6][7][8][9][10] The ideal double perovskite structure of the general formula A 2 BCO 6 is constructed with the B cation substituted partially by a C cation in an ordered 1:1 way in the ideal perovskite structure ABO 3 . Monoclinic, tetragonal, trigonal, and cubic structures have been discovered in this family, [11][12][13][14][15] some of which display this sequence on increase of temperature.…”