Manganese Luminescent Centers of Different Valence in Yttrium Aluminum Borate Crystals.

We present an extensive study of the luminescence characteristics of Mn impurity ions in a YAl 3 (BO 3 ) 4 :Mn crystal, in combination with X-ray fluorescence analysis and determination of the valence state of Mn by XANES (X-ray absorption near-edge structure) spectroscopy. The valences of manganese Mn 2+ (d 5 ) and Mn 3+ (d 4 ) were determined by the XANES and high-resolution optical spectroscopy methods shown to be complementary. We observe the R 1 and R 2 luminescence and absorption lines characteristic of the 2 E ↔   4 A 2 transitions in d 3 ions (such as Mn 4+ and Cr 3+ ) and show that they arise due to uncontrolled admixture of Cr 3+ ions. A broad luminescent band in the green part of the spectrum is attributed to transitions in Mn 2+ . Narrow zero-phonon infrared luminescence lines near 1060 nm (9400 cm -1 ) and 760 nm (13,160 cm -1 ) are associated with spin-forbidden transitions in Mn 3+ : 1 T 2 → 3 T 1 (between excited triplets) and 1 T 2 → 5 E (to the ground state). Spin-allowed 5 T 2 → 5 E Mn 3+ transitions show up as a broad band in the orange region of the spectrum. Using the data of optical spectroscopy and Tanabe-Sugano diagrams we estimated the crystal-field parameter Dq and Racah parameter B for Mn 3+ in YAB:Mn as Dq = 1785 cm -1 and B = 800 cm -1 . Our work can serve as a basis for further study of YAB:Mn for the purposes of luminescent thermometry, as well as other applications.