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  • Low-Temperature Luminescenc...
    Khaidukov, N. M.; Nikonov, K. S.; Brekhovskikh, M. N.; Kirikova, N. Yu; Kondratyuk, V. A.; Makhov, V. N.

    Inorganic materials, 07/2022, Letnik: 58, Številka: 7
    Journal Article

    — Ceramic LiAl 5 O 8 lithium aluminate spinel materials doped with trivalent chromium ions have been prepared by high-temperature solid-state synthesis. The intensity, spectral shift, and width of two zero-phonon luminescence lines ( R lines) due to transitions from the 2 E excited state to the 4 A 2 ground state of Cr 3+ ions have been measured as functions of temperature in the range 80–295 K. Analysis of luminescence and luminescence excitation spectra of the ceramics points to severe local lattice distortion around the Cr 3+ ions, which shows up, in particular, as large inhomogeneous broadening of the zero-phonon Cr 3+ luminescence lines. The temperature dependences of the relative intensity, spectral shift, and width of the two zero-phonon lines can be sufficiently well described in terms of existing models for optical centers in crystals. The feasibility of using these temperature dependences for noncontact luminescence thermometry is assessed. Analysis of the data obtained in this study provides no way to uniquely identify the observed zero-phonon lines as due to transitions from two sublevels of the 2 E state of a single type of chromium center (that is, as R 1 and R 2 lines) or transitions of two inequivalent chromium centers coupled by nonresonant energy transfer.