Luminescence Properties of Spinels Doped with Manganese Ions
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HESIS AND PROPERTIES OF INORGANIC COMPOUNDS
Luminescence Properties of Spinels Doped with Manganese Ions N. M. Khaidukova, M. N. Brekhovskikha, *, N. Yu. Kirikovab, V. A. Kondratyukb, and V. N. Makhovb aKurnakov
Institute of General and Inorganic Chemistry, Russian Academy of Sciences, Moscow, 119991 Russia b Lebedev Physical Institute, Russian Academy of Sciences, Moscow, 119991 Russia *e-mail: [email protected] Received March 12, 2020; revised March 30, 2020; accepted March 31, 2020
Abstract—A method to synthesize spinel (MgAl2O4)–based compounds doped with magnesium ions was developed, which makes it possible to create red-emitting phosphors (band peak at 651 nm) or green-emitting phosphors (band peak at 525 nm) due to the luminescence of Mn4+ or Mn2+, respectively, and also phosphors that have both (red and green) emission bands. Both types of luminescence exhibit quite high thermal stability; particularly, the green luminescence does. Namely, the temperature at which the luminescence intensity halves in comparison with the maximum intensity is T0.5 = 448 and 737 K for the red (Mn4+) and green (Mn2+) luminescence, respectively. On the other hand, for the phosphors that have both emission bands, the temperature dependences of the intensities of the red and green luminescence more closely resemble each other because of the energy transfer from Mn4+ ions to Mn2+ ions. Both emission bands are efficiently excited in the blue spectral region, which enables the use of the conventional three-color RGB (red–green–blue) method to create LED white-light sources based on a combination of a blue light-emitting diode and a phosphor containing manganese ions with an optimally chosen ratio between the intensities of the green and red emission bands. Keywords: ceramics, luminescence, thermal quenching, color coordinates, white light-emitting diode DOI: 10.1134/S0036023620080069
INTRODUCTION Since recently, LED white-light sources have been extraordinarily widely used and continue to replace other, less efficient types of lamps, in particular, in indoor lighting. For this reason, the search for and development of new phosphors for such LEDs are underway to further increase their efficiency. Great attention is paid to the development of new narrowband red phosphors emitting in the range 620–650 nm for LED warm white-light sources [1]. It is well known that Mn4+ ions in the octahedral environment emit narrow-band luminescence in the red spectral region [2–13]; therefore, red phosphors doped with Mn4+ ions are considered among the most promising for using in such LEDs. A problem in LED technology is that fact that green LEDs, which emit in the spectral region that is critical for light color sensing, have much less efficiency than red and blue LEDs. This circumstance, known as “green gap,” significantly restricts the development of LEDs for many applications. One of the ways to create green LEDs is to use phosphors that efficiently convert the emission of a blue LED to green luminescence. Phosphors based on the luminescence of M
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