On the electrical conductivity, thermoelectric power and dielectric constant of Y2Ti2O7 single crystals

Pandit, Abhiyan; Ansari, T.H.; Prasad, Mahesh; Singh, R. A.; Wanklyn, B.M.

doi:10.1016/0167-577x(91)90061-a

Cited by 12 publications

(6 citation statements)

References 9 publications

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“…The optical band gap of the YTO is determined to be ∼4.93 eV from extrapolation of the linear part of the [ f ( R ∞ )hν] n plot based on the direct transition ( n = 2), as presented in the Figure c inset. This value is larger than that of any previously reported optical band gap values of YTO, which vary from 3.12, 3.44, and 3.50 to 4.32 eV . The difference between the obtained results can be reasonable.…”

Section: Resultscontrasting

confidence: 76%

Charge Transfer-Triggered Bi³⁺Near-Infrared Emission in Y₂Ti₂O₇for Dual-Mode Temperature Sensing

Wang

Jahanbazi

Wei

et al. 2022

ACS Appl. Mater. Interfaces

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Trivalent bismuth is a popular main group ion showing versatile luminescent behaviors in a broad spectral range from ultraviolet to visible, but barely in the near-infrared (NIR) region. In this study, we have observed unexpected NIR emission at ∼744 nm in a Bi3+-doped pyrochlore, Y2Ti2O7 (YTOB). Our first-principles electronic structure calculation and analysis of the Bi local structure via extended X-ray absorption fine structure indicate that only Bi3+ species appears in YTOB and it has a similar local environment to that of Y3+. The NIR emission is assigned to a Ti4+ → Bi3+ metal-to-metal charge transfer process. Moreover, we have demonstrated dual-mode luminescence thermometry based on the luminescence intensity ratio (LIR) and lifetime (τ) in 0.5% Bi3+ and 0.5% Pr3+ co-doped Y2Ti2O7 (YTOB0.5P0.5). It exhibits high thermometric sensitivity simultaneously in the cryogenic temperature range from 78 to 298 K based on τ of the NIR emission of Bi3+ at 748 nm and in the temperature range of 278–378 K based on the LIR of Bi3+ to Pr3+ emissions (I 748/I 615). As a novel LIR-τ dual-mode thermometric material over a wide temperature range, the maximum relative sensitivities of the YTOB0.5P0.5 reach 3.53% K–1 at 298 K from the τ mode and 3.52% K–1 at 318 K based on the LIR mode. The dual-mode luminescence thermometry with high responsivity from our Bi3+-based pyrochlore Y2Ti2O7 phosphor opens a new avenue for more luminescent materials toward multi-mode thermometry applied in complex temperature-sensing conditions.

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Section: Resultscontrasting

confidence: 76%

Charge Transfer-Triggered Bi³⁺Near-Infrared Emission in Y₂Ti₂O₇for Dual-Mode Temperature Sensing

Wang

Jahanbazi

Wei

et al. 2022

ACS Appl. Mater. Interfaces

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“…Bulk Y 2 Ti 2 O 7 has a direct band gap with an energy of 2.75 eV, which is smaller than the experimental value of 3.12 eV. 51 It appears that the creation of a Ti vacancy affects the valence band structure of bulk Y 2 Ti 2 O 7 by shifting the Fermi level from the bulk value of 3.26 eV to a value of 2.86 eV and creating p-type doping characteristics. However, such character cannot be reproduced by the DFT+U method, since the Fermi level shifts to a slightly higher energy level, indicating that the on-site Coulomb interaction is overcorrected.…”

Section: Resultsmentioning

confidence: 83%

Impact of point defects on electronic structure in Y2Ti2O7

2012

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“…The forbidden gap at ¥ is 2.78 eV®almost 11% smaller than the experimental value (3.12 eV). 13) Terki et al and Jiang et al have reported similar theoretical values of 2.87 14) and 2.84 eV, 15) respectively. The underestimation of bandgaps based on the local density approximation and GGA approaches is well documented; this underestimation results from the self-interaction error and the integer discontinuity in the exchange correlation energy and potential when the number of electrons is changed.…”

Section: Supercell Constructionmentioning

confidence: 72%

First-principles energy band calculation of a (Ca2+, V5+)-doped Y2Ti2O7 pigment

Matsushima

Tanaka

Ishii

et al. 2019

J. Ceram. Soc. Japan

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A first-principles energy band calculation is performed with respect to the V 5+-and (Ca 2+ , V 5+)-doped Y 2 Ti 2 O 7 supercells to elucidate the effect of Ca 2+ doping on the electronic structure and optical properties of a V 5+-doped Y 2 Ti 2 O 7 pigment in the present study. The structural optimization calculation reveals that the theoretical lattice constant of the Y 2 Ti 2 O 7 unit cell slightly increases when compared with that in the experimental data. The forbidden gap at the ¥ point is estimated to be 2.78 eV. On the basis of the density-of-states analysis, the valence band (VB) of Y 2 Ti 2 O 7 mainly comprises the O 2p states and hybridizes with the Ti 3d and Y 4d states. The conduction band (CB) can be divided into two energy regions. The lower CB comprises the Ti 3d states and hybridizes with the O 2p states, whereas the upper CB comprises the Y 4d, Ti 3d, and O 2p states. When Y 2 Ti 2 O 7 is doped with a V atom, the VB width and bandgap are observed to expand by 0.7 and 0.2 eV, respectively, with respect to the pristine Y 2 Ti 2 O 7. Two strongly localized peaks, corresponding to the V 3d states, appear in the bandgap. Further, three strongly localized peaks appear in the bandgap when V 5+-doped Y 2 Ti 2 O 7 is doped with a Ca atom. In the dielectric function calculation of the V 5+-doped Y 2 Ti 2 O 7 , there is broad absorption from the O 2p VB states to the V 3d gap states as well as a VBCB optical transition in the host crystal. When the V 5+-doped Y 2 Ti 2 O 7 is doped with a Ca atom, the distortion of the VO 6 octahedron becomes large, leading to an increment of O 2p state densities near the valence-band maximum of the host. Thus, it is considered the momentum matrix elements between occupied states (O 2p states) and unoccupied states (V 3d states) becomes large in comparison with the case before a Ca doping.

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On the electrical conductivity, thermoelectric power and dielectric constant of Y2Ti2O7 single crystals

Cited by 12 publications

References 9 publications

Charge Transfer-Triggered Bi³⁺Near-Infrared Emission in Y₂Ti₂O₇for Dual-Mode Temperature Sensing

Charge Transfer-Triggered Bi³⁺Near-Infrared Emission in Y₂Ti₂O₇for Dual-Mode Temperature Sensing

Impact of point defects on electronic structure in Y2Ti2O7

First-principles energy band calculation of a (Ca<sup>2+</sup>, V<sup>5+</sup>)-doped Y<sub>2</sub>Ti<sub>2</sub>O<sub>7</sub> pigment

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On the electrical conductivity, thermoelectric power and dielectric constant of Y2Ti2O7 single crystals

Cited by 12 publications

References 9 publications

Charge Transfer-Triggered Bi3+Near-Infrared Emission in Y2Ti2O7for Dual-Mode Temperature Sensing

Charge Transfer-Triggered Bi3+Near-Infrared Emission in Y2Ti2O7for Dual-Mode Temperature Sensing

Impact of point defects on electronic structure in Y2Ti2O7

First-principles energy band calculation of a (Ca<sup>2+</sup>, V<sup>5+</sup>)-doped Y<sub>2</sub>Ti<sub>2</sub>O<sub>7</sub> pigment

Contact Info

Product

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Charge Transfer-Triggered Bi³⁺Near-Infrared Emission in Y₂Ti₂O₇for Dual-Mode Temperature Sensing

Charge Transfer-Triggered Bi³⁺Near-Infrared Emission in Y₂Ti₂O₇for Dual-Mode Temperature Sensing