TY  - JOUR
AU  - Srivastava, Alok M.
AU  - Brik, Mikhail G.
AU  - Beers, William W.
AU  - Ma, Chong-Geng
AU  - Piasecki, Michal
AU  - Cohen, William E.
PY  - 2023
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/10610
AB  - A comparative study of Eu3+ luminescence in an isostructural series of phosphate and vanadate compounds correlates the hypersensitivity of the 5D0→7F2 transition to the covalence and polarizability of the (XO4)3- (X = P, V) polyanion. The intensity of this transition, as measured by the ratio, [Formula presented], is always higher in the vanadate system [R (PO4)3-« R (VO4)3-]. Electronic energy band structure of these systems establishes higher covalence and polarizability of the (VO4)3- polyanion, which is due to strong V 3 d - O 2p covalent interaction via hybridization. The difference in the intensity of the hypersensitive transition between the phosphate and vanadate systems is consistent with the prediction of the ligand dipolar polarization model for the 4f-4f dipolar intensities. Our analysis supports the polarizability of (XO4)3- (X = P, V) over local site distortion effects as the intensity enhancing mechanism of the 5D0→7F2 transition. It is pointed out that the hybridization effect that serves as the source of the intensity of hypersensitive transition also accounts for the origin of second harmonic generation (SHG) in Li3VO4 and its absence in Li3PO4. © 2023 Elsevier B.V.
T2  - Journal of Luminescence
T1  - Intensity of the Eu3+ hypersensitive transition in isostructural phosphate and vanadate compounds
VL  - 257
DO  - 10.1016/j.jlumin.2023.119709
ER  - 

@article{
author = "Srivastava, Alok M. and Brik, Mikhail G. and Beers, William W. and Ma, Chong-Geng and Piasecki, Michal and Cohen, William E.",
year = "2023",
abstract = "A comparative study of Eu3+ luminescence in an isostructural series of phosphate and vanadate compounds correlates the hypersensitivity of the 5D0→7F2 transition to the covalence and polarizability of the (XO4)3- (X = P, V) polyanion. The intensity of this transition, as measured by the ratio, [Formula presented], is always higher in the vanadate system [R (PO4)3-« R (VO4)3-]. Electronic energy band structure of these systems establishes higher covalence and polarizability of the (VO4)3- polyanion, which is due to strong V 3 d - O 2p covalent interaction via hybridization. The difference in the intensity of the hypersensitive transition between the phosphate and vanadate systems is consistent with the prediction of the ligand dipolar polarization model for the 4f-4f dipolar intensities. Our analysis supports the polarizability of (XO4)3- (X = P, V) over local site distortion effects as the intensity enhancing mechanism of the 5D0→7F2 transition. It is pointed out that the hybridization effect that serves as the source of the intensity of hypersensitive transition also accounts for the origin of second harmonic generation (SHG) in Li3VO4 and its absence in Li3PO4. © 2023 Elsevier B.V.",
journal = "Journal of Luminescence",
title = "Intensity of the Eu3+ hypersensitive transition in isostructural phosphate and vanadate compounds",
volume = "257",
doi = "10.1016/j.jlumin.2023.119709"
}

Srivastava, A. M., Brik, M. G., Beers, W. W., Ma, C., Piasecki, M.,& Cohen, W. E.. (2023). Intensity of the Eu3+ hypersensitive transition in isostructural phosphate and vanadate compounds. in Journal of Luminescence, 257.
https://doi.org/10.1016/j.jlumin.2023.119709

Srivastava AM, Brik MG, Beers WW, Ma C, Piasecki M, Cohen WE. Intensity of the Eu3+ hypersensitive transition in isostructural phosphate and vanadate compounds. in Journal of Luminescence. 2023;257.
doi:10.1016/j.jlumin.2023.119709 .

Srivastava, Alok M., Brik, Mikhail G., Beers, William W., Ma, Chong-Geng, Piasecki, Michal, Cohen, William E., "Intensity of the Eu3+ hypersensitive transition in isostructural phosphate and vanadate compounds" in Journal of Luminescence, 257 (2023),
https://doi.org/10.1016/j.jlumin.2023.119709 . .

TY  - JOUR
AU  - Srivastava, Alok M.
AU  - Brik, Mikhail
AU  - Beers, William W.
AU  - Lou, B.
AU  - Ma, C.-G.
AU  - Piasecki, Michal
AU  - Cohen, William E.
PY  - 2023
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/11170
AB  - A comparative study of Eu3+ ion luminescence in YXO4 (X=P, As, V) with the tetragonal zircon structure is conducted in relation to the intensity of the hypersensitivity 5D0 → 7F2 Δ J = 2 transition. Both the asymmetry ratio, R = I 5 D 0 − 7 F 2 I 5 D 0 − 7 F 1 , and the Judd-Ofelt Ω2 intensity parameter increases in the order YPO4 < YAsO4 < YVO4. This correlation is interpreted qualitatively in terms of the covalency and polarizability of (XO4)3−, which increases in the order (PO4)3− < (AsO4)3− < (VO4)3−. The trend is supported by the results of electronic band structure calculations of the three compounds which establish the strength of hybridization between the X cation and the oxygen 2p states. The electronic structure of YAsO4 is calculated to probe the covalence of As-O bonding. The increasing oscillator strength of the Eu3+5D0 → 7F2 transition in going from YPO4 to YAsO4 to YVO4 is consistent with the expectation of ligand dipolar polarization model for hypersensitivity which states that the oscillator strength of the 5D0 → 7F2 transition is proportional to the square of the ligand dipolar polarizability. The connection between the mechanism of hypersensitivity and second harmonic generation (SHG) is presented. © 2023 The Electrochemical Society (“ECS”). Published on behalf of ECS by IOP Publishing Limited.
T2  - ECS Journal of Solid State Science and Technology
T1  - Orbital Hybridization and Hypersensitivity of Eu3+ in YXO4 (X=P, As, V)
VL  - 12
IS  - 6
SP  - 066001
DO  - 10.1149/2162-8777/acd80f
ER  - 

@article{
author = "Srivastava, Alok M. and Brik, Mikhail and Beers, William W. and Lou, B. and Ma, C.-G. and Piasecki, Michal and Cohen, William E.",
year = "2023",
abstract = "A comparative study of Eu3+ ion luminescence in YXO4 (X=P, As, V) with the tetragonal zircon structure is conducted in relation to the intensity of the hypersensitivity 5D0 → 7F2 Δ J = 2 transition. Both the asymmetry ratio, R = I 5 D 0 − 7 F 2 I 5 D 0 − 7 F 1 , and the Judd-Ofelt Ω2 intensity parameter increases in the order YPO4 < YAsO4 < YVO4. This correlation is interpreted qualitatively in terms of the covalency and polarizability of (XO4)3−, which increases in the order (PO4)3− < (AsO4)3− < (VO4)3−. The trend is supported by the results of electronic band structure calculations of the three compounds which establish the strength of hybridization between the X cation and the oxygen 2p states. The electronic structure of YAsO4 is calculated to probe the covalence of As-O bonding. The increasing oscillator strength of the Eu3+5D0 → 7F2 transition in going from YPO4 to YAsO4 to YVO4 is consistent with the expectation of ligand dipolar polarization model for hypersensitivity which states that the oscillator strength of the 5D0 → 7F2 transition is proportional to the square of the ligand dipolar polarizability. The connection between the mechanism of hypersensitivity and second harmonic generation (SHG) is presented. © 2023 The Electrochemical Society (“ECS”). Published on behalf of ECS by IOP Publishing Limited.",
journal = "ECS Journal of Solid State Science and Technology",
title = "Orbital Hybridization and Hypersensitivity of Eu3+ in YXO4 (X=P, As, V)",
volume = "12",
number = "6",
pages = "066001",
doi = "10.1149/2162-8777/acd80f"
}

Srivastava, A. M., Brik, M., Beers, W. W., Lou, B., Ma, C.-G., Piasecki, M.,& Cohen, W. E.. (2023). Orbital Hybridization and Hypersensitivity of Eu3+ in YXO4 (X=P, As, V). in ECS Journal of Solid State Science and Technology, 12(6), 066001.
https://doi.org/10.1149/2162-8777/acd80f

Srivastava AM, Brik M, Beers WW, Lou B, Ma C, Piasecki M, Cohen WE. Orbital Hybridization and Hypersensitivity of Eu3+ in YXO4 (X=P, As, V). in ECS Journal of Solid State Science and Technology. 2023;12(6):066001.
doi:10.1149/2162-8777/acd80f .

Srivastava, Alok M., Brik, Mikhail, Beers, William W., Lou, B., Ma, C.-G., Piasecki, Michal, Cohen, William E., "Orbital Hybridization and Hypersensitivity of Eu3+ in YXO4 (X=P, As, V)" in ECS Journal of Solid State Science and Technology, 12, no. 6 (2023):066001,
https://doi.org/10.1149/2162-8777/acd80f . .

TY  - JOUR
AU  - Srivastava, Alok M.
AU  - Brik, Mikhail G.
AU  - Beers, William W.
AU  - Cohen, William E.
PY  - 2022
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/10601
AB  - The relationship between the Stokes shift of Bi3+ emission and the volume of the unit-cell in two series of orthorhombic perovskites, LnB 3+O3 (Ln = La, Gd, Y; B 3+ = Al, In, Ga) and AB 4+O3 (A = Ca, Sr; B 4+ = Zr, Sn) is explored. The Stokes shift increases linearly with increasing cell volume. This is explained qualitatively by the lattice chemical pressure acting on the Bi3+ ion. The degree of Bi3+ ion off-centering displacement, which is due to the stereochemical activity of the lone-pair electrons (6 s2), is controlled by the chemical pressure. A small cell suppresses the off-centering displacement to produce a small Stokes shift of emission by limiting the excited state structural distortion. In large cell, the off-centering displacement is more easily accommodated. The elimination of ground state distortion in the excited state gives larger Stokes shift of emission. These qualitative arguments are supplemented by recent first-principles calculations on Bi3+ luminescence in these perovskites. The Bi3+ luminescence in SrZrO3, previously assigned to emission from the D-state, is now assigned to the localized 3P0,1 → 1S0 transition. The energy of the 1S0 → 3P1 transition is correlated with the covalence of the BO6/2 perovskite framework. Discussion on the effective ionic radius of the Bi3+ ion in these perovskites is presented.
T2  - ECS Journal of Solid State Science and Technology
T1  - Chemical Pressure Effects on the Stokes Shift of Bi3+ Luminescence in Orthorhombic Perovskites
VL  - 11
IS  - 9
SP  - 096003
DO  - 10.1149/2162-8777/ac915b
ER  - 

@article{
author = "Srivastava, Alok M. and Brik, Mikhail G. and Beers, William W. and Cohen, William E.",
year = "2022",
abstract = "The relationship between the Stokes shift of Bi3+ emission and the volume of the unit-cell in two series of orthorhombic perovskites, LnB 3+O3 (Ln = La, Gd, Y; B 3+ = Al, In, Ga) and AB 4+O3 (A = Ca, Sr; B 4+ = Zr, Sn) is explored. The Stokes shift increases linearly with increasing cell volume. This is explained qualitatively by the lattice chemical pressure acting on the Bi3+ ion. The degree of Bi3+ ion off-centering displacement, which is due to the stereochemical activity of the lone-pair electrons (6 s2), is controlled by the chemical pressure. A small cell suppresses the off-centering displacement to produce a small Stokes shift of emission by limiting the excited state structural distortion. In large cell, the off-centering displacement is more easily accommodated. The elimination of ground state distortion in the excited state gives larger Stokes shift of emission. These qualitative arguments are supplemented by recent first-principles calculations on Bi3+ luminescence in these perovskites. The Bi3+ luminescence in SrZrO3, previously assigned to emission from the D-state, is now assigned to the localized 3P0,1 → 1S0 transition. The energy of the 1S0 → 3P1 transition is correlated with the covalence of the BO6/2 perovskite framework. Discussion on the effective ionic radius of the Bi3+ ion in these perovskites is presented.",
journal = "ECS Journal of Solid State Science and Technology",
title = "Chemical Pressure Effects on the Stokes Shift of Bi3+ Luminescence in Orthorhombic Perovskites",
volume = "11",
number = "9",
pages = "096003",
doi = "10.1149/2162-8777/ac915b"
}

Srivastava, A. M., Brik, M. G., Beers, W. W.,& Cohen, W. E.. (2022). Chemical Pressure Effects on the Stokes Shift of Bi3+ Luminescence in Orthorhombic Perovskites. in ECS Journal of Solid State Science and Technology, 11(9), 096003.
https://doi.org/10.1149/2162-8777/ac915b

Srivastava AM, Brik MG, Beers WW, Cohen WE. Chemical Pressure Effects on the Stokes Shift of Bi3+ Luminescence in Orthorhombic Perovskites. in ECS Journal of Solid State Science and Technology. 2022;11(9):096003.
doi:10.1149/2162-8777/ac915b .

Srivastava, Alok M., Brik, Mikhail G., Beers, William W., Cohen, William E., "Chemical Pressure Effects on the Stokes Shift of Bi3+ Luminescence in Orthorhombic Perovskites" in ECS Journal of Solid State Science and Technology, 11, no. 9 (2022):096003,
https://doi.org/10.1149/2162-8777/ac915b . .

TY  - JOUR
AU  - Đorđević, Vesna R.
AU  - Brik, Mikhail G.
AU  - Srivastava, Alok M.
AU  - Medić, Mina M.
AU  - Vulić, Predrag J.
AU  - Glais, Estelle
AU  - Viana, Bruno
AU  - Dramićanin, Miroslav
PY  - 2017
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/7197
AB  - Herein, the synthesis, structural and crystal field analysis and optical spectroscopy of Mn4+ doped metal titanates ATiO(3) (A = Ca, Mg) are presented. Materials of desired phase were prepared by molten salt assisted sol-gel method in the powder form. Crystallographic data of samples were obtained by refinement of X-ray diffraction measurements. From experimental excitation and emission spectra and structural data, crystal field parameters and energy levels of Mn4+ in CaTiO3 and MgTiO3 were calculated by the exchange charge model of crystal-field theory. It is found that crystalline field strength is lower (Dq = 1831 cm(-1)) in the rhombohedral Ilmenite MgTiO3 structure due to the relatively longer average Mn4+-O2- bond distance (2.059 angstrom), and higher (Dq = 2017 cm(-1)) in orthorhombic CaTiO3 which possess shorter average Mn4+-O2- bond distance (1.956 angstrom). Spectral positions of the Mn(4+2)Eg - GT (4)A(2g) transition maxima is 709 nm in MgTiO3 and 717 nm in CaTiO3 respectively in good agreement with calculated values. (C) 2017 Elsevier B.V. All rights reserved.
T2  - Optical Materials
T1  - Luminescence of Mn4+ ions in CaTiO3 and MgTiO3 perovskites: Relationship of experimental spectroscopic data and crystal field calculations
VL  - 74
SP  - 46
EP  - 51
DO  - 10.1016/j.optmat.2017.03.021
ER  - 

@article{
author = "Đorđević, Vesna R. and Brik, Mikhail G. and Srivastava, Alok M. and Medić, Mina M. and Vulić, Predrag J. and Glais, Estelle and Viana, Bruno and Dramićanin, Miroslav",
year = "2017",
abstract = "Herein, the synthesis, structural and crystal field analysis and optical spectroscopy of Mn4+ doped metal titanates ATiO(3) (A = Ca, Mg) are presented. Materials of desired phase were prepared by molten salt assisted sol-gel method in the powder form. Crystallographic data of samples were obtained by refinement of X-ray diffraction measurements. From experimental excitation and emission spectra and structural data, crystal field parameters and energy levels of Mn4+ in CaTiO3 and MgTiO3 were calculated by the exchange charge model of crystal-field theory. It is found that crystalline field strength is lower (Dq = 1831 cm(-1)) in the rhombohedral Ilmenite MgTiO3 structure due to the relatively longer average Mn4+-O2- bond distance (2.059 angstrom), and higher (Dq = 2017 cm(-1)) in orthorhombic CaTiO3 which possess shorter average Mn4+-O2- bond distance (1.956 angstrom). Spectral positions of the Mn(4+2)Eg - GT (4)A(2g) transition maxima is 709 nm in MgTiO3 and 717 nm in CaTiO3 respectively in good agreement with calculated values. (C) 2017 Elsevier B.V. All rights reserved.",
journal = "Optical Materials",
title = "Luminescence of Mn4+ ions in CaTiO3 and MgTiO3 perovskites: Relationship of experimental spectroscopic data and crystal field calculations",
volume = "74",
pages = "46-51",
doi = "10.1016/j.optmat.2017.03.021"
}

Đorđević, V. R., Brik, M. G., Srivastava, A. M., Medić, M. M., Vulić, P. J., Glais, E., Viana, B.,& Dramićanin, M.. (2017). Luminescence of Mn4+ ions in CaTiO3 and MgTiO3 perovskites: Relationship of experimental spectroscopic data and crystal field calculations. in Optical Materials, 74, 46-51.
https://doi.org/10.1016/j.optmat.2017.03.021

Đorđević VR, Brik MG, Srivastava AM, Medić MM, Vulić PJ, Glais E, Viana B, Dramićanin M. Luminescence of Mn4+ ions in CaTiO3 and MgTiO3 perovskites: Relationship of experimental spectroscopic data and crystal field calculations. in Optical Materials. 2017;74:46-51.
doi:10.1016/j.optmat.2017.03.021 .

Đorđević, Vesna R., Brik, Mikhail G., Srivastava, Alok M., Medić, Mina M., Vulić, Predrag J., Glais, Estelle, Viana, Bruno, Dramićanin, Miroslav, "Luminescence of Mn4+ ions in CaTiO3 and MgTiO3 perovskites: Relationship of experimental spectroscopic data and crystal field calculations" in Optical Materials, 74 (2017):46-51,
https://doi.org/10.1016/j.optmat.2017.03.021 . .