Review—Photoluminescence Properties of Cr³⁺-Activated Fluoride Phosphors

Abstract

The Cr3+-activated phosphor properties are discussed in detail from an aspect of spectroscopic point of view. The host materials considered here are a various kind of fluoride compounds. The photoluminescence (PL) and PL excitation spectra of such Cr3+-activated fluoride phosphors are analyzed based on Franck−Condon analysis within the configurational-coordinate model. A method is proposed for obtaining reliable crystal-field (Dq) and Racah parameters (B and C) based on a general ligand field theory with paying an attention to difficulty in the exact estimation of such important ligand field parameters. The intra-d-shell Cr3+ states, such as 2 Eg (2 G), T 2 g 4 (4 F), and T 1 g 4 (4 F), in various fluoride hosts are determined and plotted against Dq in the Tanabe−Sugano energy-level diagram. A comparative discussion of Cr3+ and Mn4+ as efficient activator ions for near-IR and red-emitting phosphors is given. Key properties of the Cr3+-activated fluoride phosphors are also presented for use of such near-IR or red-emitting fluoride phosphors in future light-emitting and related device applications.

Fundamental luminescence properties of Mn4+ activated Ca14Al10Zn6O35 phosphor

“…The larger DE 1 and the smaller DE 2 mainly affect the thermal quenching at higher and lower temperatures, respectively. 78 As shown in Fig. 8b and Fig.…”

“…Taking the radiative vibronic emissions and the nonradiative transition into consideration simultaneously, the temperature dependence of the PL intensity is proposed to be: 4,78…”

Metal–Organic Framework Optical Thermometer Based on Cr3+ Ion Luminescence

“…The luminescence properties of transition metal ions, such as Cr 3+ , originate from d–d electronic transitions, which are not shielded by the outer orbitals, unlike the 4f orbitals in trivalent lanthanide ions . Consequently, the spectroscopic characteristics of Cr 3+ ions are strongly affected by the crystal field strength of the matrix material; thus, the emission type, range, and thermal quenching rate can be tuned by changing the matrix type. − The sensitivity of spectroscopic properties to the change of crystal field parameters plays a particular role in research on TM-based luminescence thermometers. ,, The irradiation with 405 nm wavelength excites a higher 4 T 1g level. The nonradiative energy transfer causes the increase in the population of the lowest vibrational level of 2 E g .…”

A Geometrically Frustrated Family of MIIMIIIF5(H2O)2 Mixed–Metal Fluorides with Complex Magnetic Interactions

“…The Tanabe–Sugano diagram for d 3 suggested that these are 4 A 2g → 4 T 1g (P), 4 A 2g → 4 T 1g , and 4 A 2g → 4 T 2g transitions, respectively. Using the Tanabe–Sugano diagram for d 3 , the crystal field for ZnCrF 5 (H 2 O) 2 ( 5 ) was estimated as ∼15000 cm –1 (∼1.86 eV), which is in line with the reported Cr 3+ -activated fluoride phosphors . For Co 2+ - and Ni 2+ -based materials only two absorption bands originating from d–d transitions fall into the visible region, while low-energy 4 T 1g → 4 T 2g (Co 2+ ) and 3 A 2g → 3 T 2g (Ni 2+ ) transitions lie in the near-IR region and hence could not be observed with the available instrumentation.…”

“…Using the Tanabe− Sugano diagram for d 3 , the crystal field for ZnCrF 5 (H 2 O) 2 (5) was estimated as ∼15000 cm −1 (∼1.86 eV), which is in line with the reported Cr 3+ -activated fluoride phosphors. 75 For Co 2+ -and Ni 2+ -based materials only two absorption bands originating from d−d transitions fall into the visible region, while low-energy 4 T 1g → 4 T 2g (Co 2+ ) and 3 A 2g → 3 T 2g (Ni 2+ ) transitions lie in the near-IR region and hence could not be observed with the available instrumentation. The typical Co-containing inverse weberite exhibits 4 T 1g → 4 A 2g (670−700 nm) and 4 T 1g → 4 T 2g (∼505 nm) bands.…”