Eduard Madirov, Sergey V. Kuznetsov, Vasilii A. Konyushkin, Andrey N. Nakladov, Pavel P. Fedorov, Thomas Bergfeldt, Damien Hudry, Dmitry Busko, Ian A. Howard, Bryce S. Richards, Andrey Turshtov. Effect of Yb3+ and Er3+ concentration on upconversion luminescence of co-doped BaF2 single crystals. Journal of Materials Chemistry C, 2021, 9, 3493 – 3503 DOI: 10.1039/d1tc00104c