Anomalous R-Line Behaviour in Nanocrystalline Al2O3:Cr3+

Abstract

The photoluminescence spectra of Al 2 O 3 : Cr 3 nanopowder under excitation by a frequencydoubled YAG:Nd laser (l ex 532 nm) and a nitrogen-vapour pulsed laser (l ex 337:1 nm) have been studied. A considerable difference between the spectra of nanocrystalline and macrocrystalline samples has been observed. The nanocrystalline samples reveal a broad asymmetric line with the maximum at 690 nm under the YAG : Nd excitation, whereas under the nitrogen-vapour laser excitation, the broad line becomes more symmetric, and its maximum shifts by 45 nm to the longer-wavelength region. The above shift is shown to be due to a drastic change in the HuangRhys parameter of the 2 E± 4 A 2 transition. A decay of the broad line with the increase of the duration of UV illumination has been observed.

Nanophosphor aluminum oxide: Luminescence response of a potential dosimetric material

“…The growth and production of Al 2 O 3 :C has been well established and led to the development of the commercial Luxel s system. The incorporation of carbon in a reducing atmosphere during the crystal growth of a-Al 2 O 3 promotes oxygen vacancies which lead to F + and F centers, one and two electrons trapped at an oxygen vacancy, respectively, and these serve as recombination centers in Al 2 O 3 [3]. However, other synthesis techniques may lead to unique luminescence dosimetry properties and simpler synthesis procedures.…”

“…However, other synthesis techniques may lead to unique luminescence dosimetry properties and simpler synthesis procedures. In particular, unique luminescence behavior was reported in nanocrystalline Al 2 O 3 :Cr when compared to bulk [3].…”

Synthesis and Optical Properties of Al2O3:Cr3+ Powders

“…The position of the peak at 691 nm indicates that the broad band belong to the non-uniformly broadened 2 E( 2 G)→ 4 F) transitions in the Cr 3+ ions. The extended longwavelength structure of the non-uniformly broadened Rline is assigned to a vibronic tail of the pure electronic 2 E( 2 G)→ 4 A 2 ( 4 F) transitions [4]. Figure 8 shows the PL spectra of the Al 2−x Cr x O 3 samples with different mole fractions x and undergone a heattreatment at 900…”

“…6 [4][5][6]. Figure 10 shows the PLE spectra of the Al 2−x Cr x O 3 samples with x = 0.005, heat-treated at 1300…”

Pulsed cathodoluminescence of nanoscale aluminum oxide with different phase compositions

“…It is also to be noticed that PL spectrum of nanocrystalline Al 2 O 3 :Cr 3 þ powder with maximum at 740 nm can be observed under the UV-laser (l¼337, 1 nm) excitation with high average laser emission power density (0.2 W/cm 2 ) [11]. Authors supposed that excitation of alumina nanopowder by laser radiation of specified wavelength causes the 4 A 2 -4 T 1 transition in Cr 3 þ ions accompanied by phonon generation.…”