Spin-Forbidden Transitions in the Spectra of Transition Metal Ions and Nephelauxetic Effect

Brik, M.G.; Camardello, S.J.; Srivastava, A.M.; Avram, N.M.; Suchocki, A.

doi:10.1149/2.0091601jss

Cited by 203 publications

(152 citation statements)

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“…The reduction of the Racah parameters B and C for TM ions into crystalline solids is due to the delocalization of the outer d‐orbitals (nephelauxetic effect) induced by the formation of chemical bonds with ligands. Recently, Brik et al [ 19 ] have introduced a new parameter,

β_{1} = \sqrt{{(\frac{B}{B_{0}})}^{2} + {(\frac{C}{C_{0}})}^{2}}

, where B , C and B 0 , C 0 are the Racah parameters in crystal and free states, respectively ( B 0 = 918 and C 0 = 3850 cm −1 ), to describe the relationship between the energy of the 2 E g → 4 A 2g spin‐forbidden transition and the covalence of the “metal‐ligand” chemical bonds. Figure 1f shows the plot of 2 E g energy versus β 1 for a set of aluminate‐based hosts confirming the reliability of the results.…”

Section: Resultsmentioning

confidence: 99%

Effective Ratiometric Luminescent Thermal Sensor by Cr³⁺‐Doped Mullite Bi₂Al₄O₉ with Robust and Reliable Performances

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Ueda

et al. 2020

Advanced Optical Materials

121

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The design of effective optical systems featuring high thermal sensitivity able to discriminate ever smaller variations of temperature in noncontact mode is of critical importance to face the challenges brought by the modern‐day technological revolution. If from one hand, the ratiometric optical thermometers based on Boltzmann distribution are demonstrated to be characterized by a unique reliability, on the other hand, robust performances in different environments are highly desired for new applications such as in situ thermal sensing of catalytic reactions. Here, the crystal field experienced by Cr3+ in Bi2Al4O9 is investigated demonstrating the potential of this system as ratiometric self‐referencing thermal sensor being characterized by high relative sensitivity (1.24% K−1 at 290 K). The remarkable absolute sensitivity results in an exceptional low thermal resolution of ≈0.2 K, 15‐fold lower than for the conventional Nd3+‐based thermometers used in biological applications. The comparison of the performances among different systems evidences the potential of Cr3+‐based thermometers with thermal resolution even lower than the state of the art diamond. In addition, the pH dependence of the photoluminescence emission confirms a high stability also at extreme conditions of basic and acid environments and the aging effects are tested for one week.

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β_{1} = \sqrt{{(\frac{B}{B_{0}})}^{2} + {(\frac{C}{C_{0}})}^{2}}

Section: Resultsmentioning

confidence: 99%

Effective Ratiometric Luminescent Thermal Sensor by Cr³⁺‐Doped Mullite Bi₂Al₄O₉ with Robust and Reliable Performances

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Ueda

et al. 2020

Advanced Optical Materials

121

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“…More details about this remarkable feature of these two energy levels can be found in recent publications. 20,21 It is obvious that if Dq = 0, we recover the energy level scheme of a free ion. With increasing Dq we see how the energy levels are split and how they behave.…”

Section: Electronic Properties Of Ions With D 3 Electron Configuratiomentioning

confidence: 99%

Critical Review—A Review of the Electronic Structure and Optical Properties of Ions with d³Electron Configuration (V²⁺, Cr³⁺, Mn⁴⁺, Fe⁵⁺) and Main Related Misconceptions

Brik

Srivastava

2017

ECS J. Solid State Sci. Technol.

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Tetravalent manganese ions with the 3d 3 electronic configuration have recently began to play a major role as a red photon generator in the LED based lighting and display devices. The goal of this article is to tutorize the fundamental optical properties of Mn 4+ and to clear up some common misconceptions that we have encountered in the archival literature that pertains to the spectroscopic properties of this ion and other ions with the same electron configuration. The methods to properly interpret the optical spectra of these systems are also discussed. This is accomplished by presenting a discussion on the electronic properties of the free d 3 ions and the changes which occur when the ion is introduced in a crystalline lattice. It is hoped that such systematic presentation of spectroscopic properties of the d 3 ions and their variation from the free state to the crystalline solids will be useful for many researchers -mainly experimentalists -actively working in the field and will help them avoiding many mistakes when presenting their experimental results. pl). This paper is part of the JSS Focus Issue on Visible and Infrared Phosphor Research and Applications.The development in 1994 of the first high brightness LED by the Nichia Corporation was followed by a renaissance of interest in developing phosphors, which in combination with the blue LED radiation would produce white light with suitable efficacy and color rendering for general lighting applications. Basically, the research has targeted the development of custom-made new phosphors (such as the nitride and oxynitride family of materials) and changing the composition of existing phosphors (such as the garnet family of materials) to produce luminescent materials that satisfy the pertinent requirements of general illumination devices. Such phosphors have been based on the luminescence of Rare-earth (RE) and Transition metal (TM) ions. Among the improved phosphors that is devised to produce red photons in general illumination and display devices is the family of phosphors with the general formulation A 2 MF 6 activated with Mn 4+ , a TM ion with the 3d 3 electronic configuration. Since the recent commercialization of the K 2 SiF 6 :Mn 4+ phosphor there has been burgeoning interest among phosphor scientist and engineers to research and develop alternative red emitting Mn 4+ activated phosphors. According to the Web of Science data base, the number of research papers containing two key words "phosphor" and "Mn 4+ " increased from nearly 0 in 2007 to more than 80 in 2016, with the number of citations going up to about 1500 in 2016 alone (Fig. 1). 1 Having seen such a reviving interest in the Mn 4+ doped phosphors, on one hand, and having met several incorrect statements in some of those papers, on the other hand, we deemed it necessary to write a tutorial review of basic spectroscopic properties of such systems with a clear aim of helping scientists, mainly targeting the young and experimental researchers, to avoid simple mistakes and basic misunderstanding. ...

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“…The energy position of the Mn 4+ 2 E g state can be altered by controlling the strength of Mn 4+ -ligand covalent mixing. [13][14][15] Literature data reveals that the energy of the 2 E g → 4 A 2g transition changes little in fluoride compounds and varies greatly in oxides. 13,14 This is because variation in covalence is smaller in fluorides than in oxides.…”

Section: Crystal Structure Of α-Lialomentioning

confidence: 99%

Interpretation of the Spectroscopic Properties of α-LiAlO₂: Mn⁴⁺

Srivastava

Brik

2017

ECS J. Solid State Sci. Technol.

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The energy position of the 2 E g → 4 A 2g emission transition of Mn 4+ in α-LiAlO 2 is identified and the electronic energy levels calculated using the exchange charge model of crystal field theory. The results of our calculations yield the crystal field splitting and Racah parameters of Dq = 2351 cm −1 , B = 650 cm −1 and C = 3469 cm −1 , with C/B = 5.3. The calculated Mn 4+ energy levels are in good agreement with the experimental spectra that have been presented in the literature. A study that develops the relationship between the energy of the 2 anions. The Mn 4+ with the 3d 3 electronic configuration prefers to occupy an octahedral site due to the attainment of large crystal field stabilization energy when each of the 3d electron occupy singly each t 2g orbital. The Mn 4+ will occupy the Al 3+ site in α-LiAlO 2 due to closeness in the electronic charges and ionic radii; the Shannon and Prewitt ionic radii for Al 3+ = 67 pm, Mn 4+ = 68 pm and Li + = 88 pm, respectively.4 Charge compensation could be attained via cation vacancies. The hexagonal α-LiAlO 2 transformed to the tetragonal (γ) modification beyond 700 C. 3 The latter structure which was fully formed at 900• C does not support Mn 4+ luminescence because in this structure the Al 3+ ions occur in tetrahedral coordination. Although the local symmetry differs from the ideal O h , in what follows we shall use the "cubic" crystal field notation t 2g and e g , and we shall denote by those symbols the groups of levels arising from the t 2g and e g states after they are split by the low symmetry component of crystal field. We shall also keep the cubic crystal field notations for the groups of levels arising from the split orbital triplets and doublets of the Mn 4+ ions.The energy of the Mn 4+ 2 E g → 4 A 2g emission transition in α-LiAlO 2 is not properly identified in the work of Aoyama et al. 3 The purpose of this paper is to identify the energy position of this transition and to calculate the electronic energy levels using the exchange charge model of crystal field theory. The calculated energy levels are compared with the experimental data. The calculations yield the extraction of three principal physical parameters of interest (1) the crystal field splitting (10Dq) and, (2) the Racah parameters, B and C. In this paper, we also develop relationship between the energy of the 2 E g → 4 A 2g emission transition with the connectivity of the octahedral moieties and the deviation of O-Mn-O bond angle in the equatorial plane from the ideal value of 90• . * Electrochemical Society Member. z E-mail: srivastava@ge.com Crystal Structure of α-LiAlO 2The structural modification of LiAlO 2 studied in the present work is described by the R-3m space group (No. 166), 2 with the lattice constants (in Å) a = b = 2.8003, c = 14.216 and three formula units per unit cell. One unit cell of α-LiAlO 2 is depicted in Fig. 1. Both Li and Al ions are six-fold coordinated by the oxygen ions forming trigonally distorted octahedra. The Li-O bond distances are 2.11 Å and the Al-O bond ...

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Spin-Forbidden Transitions in the Spectra of Transition Metal Ions and Nephelauxetic Effect

Cited by 203 publications

References 169 publications

Effective Ratiometric Luminescent Thermal Sensor by Cr³⁺‐Doped Mullite Bi₂Al₄O₉ with Robust and Reliable Performances

Effective Ratiometric Luminescent Thermal Sensor by Cr³⁺‐Doped Mullite Bi₂Al₄O₉ with Robust and Reliable Performances

Critical Review—A Review of the Electronic Structure and Optical Properties of Ions with d³Electron Configuration (V²⁺, Cr³⁺, Mn⁴⁺, Fe⁵⁺) and Main Related Misconceptions

Interpretation of the Spectroscopic Properties of α-LiAlO₂: Mn⁴⁺

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Spin-Forbidden Transitions in the Spectra of Transition Metal Ions and Nephelauxetic Effect

Cited by 203 publications

References 169 publications

Effective Ratiometric Luminescent Thermal Sensor by Cr3+‐Doped Mullite Bi2Al4O9 with Robust and Reliable Performances

Effective Ratiometric Luminescent Thermal Sensor by Cr3+‐Doped Mullite Bi2Al4O9 with Robust and Reliable Performances

Critical Review—A Review of the Electronic Structure and Optical Properties of Ions with d3Electron Configuration (V2+, Cr3+, Mn4+, Fe5+) and Main Related Misconceptions

Interpretation of the Spectroscopic Properties of α-LiAlO2: Mn4+

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Effective Ratiometric Luminescent Thermal Sensor by Cr³⁺‐Doped Mullite Bi₂Al₄O₉ with Robust and Reliable Performances

Effective Ratiometric Luminescent Thermal Sensor by Cr³⁺‐Doped Mullite Bi₂Al₄O₉ with Robust and Reliable Performances

Critical Review—A Review of the Electronic Structure and Optical Properties of Ions with d³Electron Configuration (V²⁺, Cr³⁺, Mn⁴⁺, Fe⁵⁺) and Main Related Misconceptions

Interpretation of the Spectroscopic Properties of α-LiAlO₂: Mn⁴⁺