Host Dependency of Boundary between Strong and Weak Crystal Field Strength of Cr³⁺ Luminescence

Abstract

Cr 3+ doped near-infrared phosphors hold significant applications and generate considerable research interest. The critical parameter for assessing the strength of the crystal field for Cr 3+ in the Tanabe−Sugano diagram is the boundary value of Dq/B, representing the ratio of crystal field splitting to the Racah parameter B. Nevertheless, there are conflicting values for this parameter, as reported in various studies, such as 2.1, 2.2, and 2.3 for C/B = 4.5−4.8. Moreover, some Cr 3+ doped phosphors with wide-band emissions exhibit a Dq/B value that falls within the region of a contradictory strong field. In this study, we numerically determine the boundary value of Dq/B, which distinguishes between strong and weak fields. The results then demonstrate a dependence on the host material and are correlated with the values of Racah parameters B and C. This work resolves the inconsistency between the boundary values of Dq/B and the emission profile of Cr 3+ , providing researchers with a more profound comprehension of Cr 3+ luminescence.

Blue light-excited broadband NIR-II-emitting Li2ZnSn3O8:Cr3+,Ni2+ phosphor for multifunctional optical applications

“…The online calculation program developed by Song et al was used to calculate the D q / B values related to the matrix for the 3d 3 electronic configuration of Cr 3+ . 38 The calculated intersection points for the 2 E and 4 T 2 levels were found to be at 1.94, with the sample's D q / B value at 2.13, close to the intersection point value. The crystal field strength in octahedrally coordinated approximation of Ni 2+ can be calculated using eqn (S1) and (S2) †.…”

Two-Site Occupation for Constructing Double Perovskite BaLaMgNbO6:Cr3+ Ultrabroadband NIR Phosphors

“…However, the typical Tanabe–Sugano diagram is designed according to the ideal octahedron and does not apply to all hosts. According to the online calculation program of transition metal 3d 3 electronic configuration energy level developed by Song et al, the D q /B value dependent on the host is calculated, as shown in Figure c. The calculated intersection point of 2 E and 4 T 2 is 2.04, and the D q /B value of the prepared sample is 2.29, which is close to the intersection value.…”