Change in the state of $Eu^{2+}$ ions in phosphors $BaMg_2Al_{16}O_{27}:Eu^{2+}$ and $(Sr,Ba)_5(PO_4)_3Cl:Eu^{2+}$ during annealing in argon

The authors investigate the effect of high temperature annealing in argon on the EPR spectra and luminescence of $Eu^{2+}$ ions in the grounds of the phosphors $BaMg_2Al_{16}O_{27}$ and $(Sr,Ba)_5(PO_4)_3Cl$. It was found that annealing leads to diffusion of argon atoms inside the crystal lattice phosphors, blocking the diffusion of oxygen, resulting in high temperatures observed in the oxidation of europium ions. It is established that annealing in argon the modification of the crystal structure of phosphors occurs at higher temperatures than in air.