Racah Parameter Ratio C/B for the 3d³-Configuration Ions Like Mn⁴⁺and Cr³⁺in the Tanabe-Sugano Diagram

Abstract

The 3d 3 -configuration transition metal ions like Mn 4+ and Cr 3+ are very important activator ions for the realization of warm white-LED lighting and indoor plant cultivation applications using an UV/blue-chip InGaN device. The Racah parameters in conjunction with the Tanabe−Sugano energy-level diagram are widely used as a means of describing the effects of electron−electron repulsion within the transition metal complexes in coordination chemistry. In constructing the Tanabe−Sugano diagram for specific ions of 3d n configuration, an approximate value of C/B is assumed and an excited-state energy divided by B is plotted as a function of Dq/B. Once the various optical spectra have been identified a more refined comparison can then be made between theory and experiment, and more accurate values of Dq (crystal-field strength), B and C can be deduced. The present study discusses an importance of the Racah parameter ratio C/B ≡ r for better understanding of the Tanabe−Sugano energy-level diagram. A new calculation model for the Racah and related parameters is reported for this purpose. A comparison of its results with the generally accepted model results is made by focusing on the Mn 4+ -activated phosphors. Results are successfully interpreted by considering a value of r = 4.7 for such phosphors.

A novel red phosphor Cs2NaGaF6:Mn4+ with ultra-strong zero-phonon lines and long wavelength phonon sidebands for high-quality WLEDs

“…The “ZPL” energy is clearly different from a maximum or a peak energy of such excited states (especially, the 4 T 2g and 4 T 1g states give the overestimated energy values) and, therefore, the Racah parameter calculations sometimes resulted in unreliable values. 37,38 Nevertheless, in some cases eqn (1) and (2) provided values that look plausible. This may be because such overestimated 4 T 2g and 4 T 1g values favorably cancelled out each other.…”

A novel Mn4+-activated fluoride red phosphor Cs30(Nb2O2F9)9(OH)3·H2O:Mn4+ with good waterproof stability for WLEDs

“…2b and c). [41][42][43][44] Several coupled sharp red-light emission peaks occurred in the emission spectrum, resulting from the spin-forbidden transition from 2 E g to 4 A 2 coordinated with the anti-symmetric odd-parity vibronic transitions n 3 (T 1u ), n 4 (T 1u ), and n 6 (T 2u ), which can be sequentially divided into a duplicate degenerate state and a non-degenerate state (Fig. 2b).…”

Derivation of Dq/B and C/B from Electronic Spectra of Transition Metal Ions in Cubic Fields Using Auxiliary Tanabe–Sugano Diagrams

“…Nevertheless, as shown recently, the Racah parameter C plays an important role in the nephelauxetic effect and in the covalency of the metal–ligand bond for ions like Mn 4+ , Cr 3+ and Ni 2+ in several crystal hosts . Ignoring the relevance of the Racah parameter C is more dramatic when trying to explain the students the position of the spin-forbidden signals since it depends on C . − Discussion of the spin-forbidden signals in the classroom is essential for introducing the students the laser effect. , In fact, the observation of both spin-allowed and spin-forbidden d–d electronic transitions in a single complex has been implemented in the laboratory at the undergraduate level, for instance using [Cr­(oxalate) 3 ] 3– (aq) or [Al 2 O 3 :Cr 3+ ](s) . Therefore, the relevance of both Racah parameters in the nephelauxetic effect and the necessity of explaining with detail, i.e.…”