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

Abstract

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. ...

Multimodal Non-Contact Luminescence Thermometry with Cr-Doped Oxides

“…It should be noted that the extent to which these characteristics are investigated and discussed is determined by the potential for application in non-contact luminescence cryothermometry. A more comprehensive discussion of the optical properties in question can be found elsewhere (see References [ 39 , 41 , 63 , 64 ] and also the papers quoted throughout this work).…”

“…The luminescence excitation spectra consist of two broad excitation bands assigned to the 4 A 2 → 4 T 1g (Y-band) and 4 A 2 → 4 T 2g (U-band) transitions of Cr 3+ in the 350–500 nm and 500–650 nm wavelength range, respectively. The excitation spectra measured at low temperature exhibit a sharp line structure at the low-energy side of the main bands attributed to the zero-phonon transitions to the 4 T 1g , 4 T 2g levels of Cr 3+ , and/or appropriate doublet 2 T 1g,2g levels [ 63 ]. The position of these bands is defined by the strength of the crystal field and Racah parameters B and C. The excitation band emerging below 350 nm in Ga 2 O 3 -Cr is due to charge transfer transitions from O 2− to Cr 3+ [ 65 ].…”

Analysis of crystal-field effect on luminescence spectra of Mn4+ (3d3) ion-doped double perovskite La2ZnTiO6 phosphor by semiempirical computations: exchange charge model and superposition model

“…However, the calculated energy of the 2 T 2g level differs from the observed energy; this difference may be attributed to the uncertainty in the experimental determination of the spinforbidden 4 A 2g -2 T 2g transition, which borrows intensity from the allowed transitions due to the presence of the spin-orbit and electron-vibrational interactions. 14,20,40,66 Let us discuss the reliability of the two sets of CFPs and the so-obtained energies. To match the calculated and observed energies 14,20 for Mn 4+ ions in La 2 ZnTiO 6 satisfactorily, the parameter G was varied using the structural data A 33 from 8.88 to 7.8, and from 9.41 to 8.325 using the structural data B.…”

Combustion Synthesis of Some Cr3+-Activated Aluminate Phosphors

“…It can be seen that parameters B and C are reduced compared to the free ion values 918 and 3850 cm -1 , respectively [50]. This reduction is due to the so-called "nephelauxetic" effect: delocalization of the 3d electrons of the activator ions because of formation of the chemical bonds with ligands [51]. Such chemical bonds are due to the overlap of the corresponding ions' wave functions and such an overlap varies strongly from one host lattice to another, depending on the Aluminate phosphors activated by Cr 3+ can be easily prepared by combustion synthesis.…”