Electron paramagnetic resonance absorption studies of (Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;)&lt;sub&gt;1-x&lt;/sub&gt; (Cr&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;)&lt;sub&gt;x&lt;/sub&gt; with controlled neutron treatments

Wenzel, Richard F.

doi:10.2172/4311973

Cited by 1 publication

(5 citation statements)

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“…Cr 3+ in the d 3 configuration is an ESR active ion, and the ESR technique was expected to effectively detect the differences in the electronic structures affected by the coordination environment. Figure 8 compares the ESR spectra of 0.5% Cr 3+ doped α-Al 2 O 3 (a), LiAl 5 O 8 (b), and ALFO (c) prepared at 1200 • C. Cr 3+ in α-Al 2 O 3 was focused on in the 1960s as a good model example for ESR measurements [44,[50][51][52][53][54][55][56][57][58]. The ESR signal of Cr 3+ in α-Al 2 O 3 (Figure 8a) was consistent with those reported for Cr 3+ in polycrystalline α-Al 2 O 3 in the previous literature [50] and consisted of several peaks corresponding to g = 3.79, 2.26, 1.72, and 1.46.…”

Section: Local Environments Around Cr 3+mentioning

confidence: 99%

“…For octahedrally coordinated d 3 ions placed in a magnetic field, the lowest energy state is the spin quartet, with the spin quantum number s = −3/2 along the direction of the magnetic field. The signal of a polycrystalline sample is the average of the spectra of individual crystallites, and the angular dependence of Cr 3+ in single crystalline Al 2 O 3 [59] indicated that the peaks at g = 3.79 and 2.26 were assigned to the s = −3/2 to −1/2 transition, and the peaks at g = 1.72 and 1.46 to the −1/2 to +1/2 transition and +1/2 to +3/2 transition, respectively (Appendix B) [50,51]. in ALFO and LiAl5O8.…”

Section: Local Environments Around Cr 3+mentioning

confidence: 99%

“…Figure 8 compares the ESR spectra of 0.5% Cr 3+ doped α-Al2O3 (a), LiAl5O8 (b), and ALFO (c) prepared at 1200 °C. Cr 3+ in α-Al2O3 was focused on in the 1960s as a good model example for ESR measurements [44,[50][51][52][53][54][55][56][57][58]. The ESR signal of Cr 3+ in α-Al2O3 (Figure 8a) was consistent with those reported for Cr 3+ in polycrystalline α-Al2O3 in the previous literature [50] and consisted of several peaks corresponding to g = 3.79, 2.26, 1.72, and 1.46. octahedrally coordinated d 3 ions placed in a magnetic field, the lowest energy state is the spin quartet, with the spin quantum number s = −3/2 along the direction of the magnetic field.…”

Section: Local Environments Around Cr 3+mentioning

confidence: 99%

“…The ESR signal of Cr 3+ in α-Al2O3 (Figure 8a) was consistent with those reported for Cr 3+ in polycrystalline α-Al2O3 in the previous literature [50] and consisted of several peaks corresponding to g = 3.79, 2.26, 1.72, and 1.46. octahedrally coordinated d 3 ions placed in a magnetic field, the lowest energy state is the spin quartet, with the spin quantum number s = −3/2 along the direction of the magnetic field. The signal of a polycrystalline sample is the average of the spectra of individual crystallites, and the angular dependence of Cr 3+ in single crystalline Al2O3 [59] indicated that the peaks at g = 3.79 and 2.26 were assigned to the s = −3/2 to −1/2 transition, and the peaks at g = 1.72 and 1.46 to the −1/2 to +1/2 transition and +1/2 to +3/2 transition, respectively (Appendix B) [50,51]. Cr 3+ in LiAl5O8 showed essentially the same ESR signal (Figure 8b) as reported by Singh et al [45] for LiAl5O8:Cr 3+ .…”

Section: Local Environments Around Cr 3+mentioning

confidence: 99%

“…According to de Biasi [59], the ESR peaks of a polycrystalline α-Al 2 O 3 :Cr 3+ sample occur at θ ≈ 40 • and 90 • , the angle (θ) between the direction of the applied magnetic field and the z axis. From the angle dependence of the ESR signal of a Cr 3+ -doped α-Al 2 O 3 single crystal [51], the peaks were assigned as shown in Table S3 in Supplementary Materials.…”

Section: Supplementary Materialsmentioning

confidence: 99%

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Deep Red Photoluminescence from Cr3+ in Fluorine-Doped Lithium Aluminate Host Material

Kamada,

Hayasaka,

Uchida

et al. 2024

Materials

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Deep red phosphors have attracted much attention for their applications in lighting, medical diagnosis, health monitoring, agriculture, etc. A new phosphor host material based on fluorine-doped lithium aluminate (ALFO) was proposed and deep red emission from Cr3+ in this host material was demonstrated. Cr3+ in ALFO was excited by blue (~410 nm) and green (~570 nm) rays and covered the deep red to near-infrared region from 650 nm to 900 nm with peaks around 700 nm. ALFO was a fluorine-doped form of the spinel-type compound LiAl5O8 with slightly Li-richer compositions. The composition depended on the preparation conditions, and the contents of Li and F tended to decrease with preparation temperature, such as Al4.69Li1.31F0.28O7.55 at 1100 °C, Al4.73Li1.27F0.17O7.65 at 1200 °C, and Al4.83Li1.17F0.10O7.78 at 1300 °C. The Rietveld analysis revealed that ALFO and LiAl5O8 were isostructural with respect to the spinel-type lattice and in a disorder–order relationship in the arrangement of Li+ and Al3+. The emission peak of Cr3+ in LiAl5O8 resided at 716 nm, while Cr3+ in ALFO showed a rather broad doublet peak with the tops at 708 nm and 716 nm when prepared at 1200 °C. The broad emission peak indicated that the local environment around Cr3+ in ALFO was distorted, which was also supported by electron spin resonance spectra, suggesting that the local environment around Cr3+ in ALFO was more inhomogeneous than expected from the diffraction-based structural analysis. It was demonstrated that even a small amount of dopant (in this case fluorine) could affect the local environment around luminescent centers, and thus the luminescence properties.

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