Structural Characterization of B-Site Ordered Ba₂Ln_2/3TeO₆ (Ln = La, Pr, Nd, Sm, and Eu) Double Perovskites and Probing Its Luminescence as Eu³⁺ Phosphor Hosts

Abstract

BaLnTeO (Ln = La, Pr, Nd, Sm, and Eu) double perovskites were synthesized via solid-state ceramic route. Preliminary X-ray diffraction studies indicated a pseudocubic structure with lattice parameters ranging from 8.55 to 8.44 Å for the substitution of rare earths from La to Eu. Raman spectra show the frequency dependence of various Raman bands with respect to rare-earth substitution and exhibit a significant shift in peaks to higher wavenumber region, which was observed only for symmetric stretching modes of LnO and TeO octahedra. In accordance with observed number of bands and group theoretical predictions, the most likely symmetry of all compounds in the BaLnTeO system was found to be monoclinic with P2 /n space group. Rietveld refinement of the XRD patterns further confirmed the P2 /n space group and also the 1:1 rock salt ordering of the B-site cations. Diffuse reflectance spectra of BaLnTeO showed the optical bandgaps of these compounds between 3.9 and 4.8 eV, indicating the suitability as luminescent host material. The reduction in bandgap energy with lanthanide contraction of rare-earth ions is attributed to the widening of conduction band with octahedral tilting. Photoluminescence (PL) spectra and PL excitation spectra of BaLaEu TeO ( x = 0.025, 0.05, 0.075, 0.1, 0.125, 0.15) were investigated and found to exhibit bright orange-red emission under UV excitation. Chromaticity coordinates closely resemble those of commercial red phosphor SrSiN:Eu, which points toward the possible applicability of these new red phosphors in solid-state lighting industry. Finally, Judd-Ofelt intensity parameters Ω (λ = 2 and 4) were calculated, which indicate that Eu ions occupy the symmetric octahedral B-site of the BaLaTeO.

Near infrared mechanoluminescence from Sr3Sn2O7: Nd3+for in situ biomechanical sensor and dynamic pressure mapping

“…The refinement process also produced lattice parameters of a = 20.676 03 Å, b = 5.728 16 Å, c = 5.710 01 Å for Sr 2.99 Sn 2 O 7 : 0.01Nd 3+ . These parameters are smaller than a = 20.68 83 Å, b = 5.736 07 Å, c = 5.710 07 Å for the blank sample, which can be ascribed to the successful substitution of larger Sr 2+ sites (R Sr 2+ = 1.41 Å for CN = 9 where CN means coordination number) by smaller Nd 3+ ions (R Nd 3+ = 1.163 Å for CN = 9) . Figure C denotes a perovskite stacked crystal structure of Sr 3 Sn 2 O 7 .…”

“…Comparison between the experimental and calculated results confirms that the sample crystallizes into orthorhombic where CN means coordination number) by smaller Nd 3+ ions (R Nd 3+ = 1.163 Å for CN = 9). 22,23 Figure 1C The SEM images of Sr 3-x Sn 2 O 7 : xNd 3+ with different Nd 3+ contents are shown in Figure 2A-F. Large amounts of intertwined columnar polyhedra are attached to the grain surfaces, and the main grain size ranges from 0.3 to 10 μm. Energy-dispersive X-ray (EDX) data of Sr 2.99 Sn 2 O 7 : 0.01Nd 3+ depicted in Figure 2G confirm that the sample is composed of Sr, Sn, O, and Nd elements, and the elements distribute uniformly throughout the samples.…”

Luminescence Properties of Rare Earth–Doped Cubic Double Perovskite Tungstate Ba2(1−x)(Na,RE)xZnWO6 (RE = Ce3+, Eu3+ and Dy3+) Phosphors

“…The RE 3þ ions interact each other through exchange and electric multipolar interaction within the host lattice, which leads to concentration quenching. [7,8,11] The mechanism of energy transfer could be identified through the calculation of the critical distance (R c ). The exchange interaction is dominant if the separation between RE 3þ ions in the host lattice is equal to or less than 5 Å, whereas for a distance larger than 5 Å the electric multipolar interaction is responsible for concentration quenching of the PL emission.…”

“…[1][2][3][4][5][6][7][8][9] Recently, perovskite materials have gained more attention for their noteworthy application in photovoltaic [6] and perovskite light-emitting diodes (LEDs). [3,4] This family of materials has proven to be the best for doping of transition metal ions [9,10] as well as rare earth ions [7,8,[11][12][13] for the enhancement of physical properties for various applications. Nevertheless, rare earth ions are preferred over transition metal ions as dopants in perovskite host lattices due to the very peculiar spectroscopic characteristics required for developing a good phosphor.…”

“…Perovskites, with their variety of new forms, interesting physical and chemical properties, and wide spectrum of applications, are one of the most extensively studied family of materials. [ 1–9 ] Recently, perovskite materials have gained more attention for their noteworthy application in photovoltaic [ 6 ] and perovskite light‐emitting diodes (LEDs). [ 3,4 ] This family of materials has proven to be the best for doping of transition metal ions [ 9,10 ] as well as rare earth ions [ 7,8,11–13 ] for the enhancement of physical properties for various applications.…”