A study of Mg2+ ions effect on atoms segregation, defects formation, luminescence and scintillation properties in Ce3+ doped Gd3Al2Ga3O12 single crystals.

• Mg2+ codoping effect on the atoms segregation in GAGG:Ce single crystal studied. • The formation of defects in Mg2+ and Ce3+ codoped GAGG crystals discussed. • The luminescence quenching mechanism in Mg2+ codoped proposed. • The charge compensation mechanism discussed. • Mg2+ codoping influence on the scintillation and luminescence properties investigated. The undoped, Mg2+ doped, Ce3+ doped as well as Mg2+:Ce3+ codoped Gd 3 Al 2 Ga 3 O 12 crystals were grown from the melt by the micro-pulling down method. Ce3+ and Mg2+ ions were codoped in a wide concentration range. A study of Mg2+ ion concentration effect on the luminescence and scintillation properties as well as segregation of atoms and defects creation processes were carried out. Mg2+ doping in Gd 3 Al 2 Ga 3 O 12 led to the creation of O O • defects localized next to Mg2+ sites due to charge imbalance compensation. Consequently, neutral (Mg Ga/Al/Gd O O) x defects were formed. In Ce3+ doped crystals, Mg2+ codoping changed the valence state from Ce3+ to Ce4+ to maintain charge neutrality. Hence, additional neutral (Ce Gd • -Mg Ga/Al/Gd ′) x and (Ce Gd -Mg Ga/Al/Gd O O) x defects appeared. Moreover, Mg2+ induced charge imbalance in GAGG crystal might also be compensated by the formation of oxygen vacancies (V O •• ). The Mg2+ ions imposed defects deteriorated the segregation of atoms. Accordingly the radial inhomogeneity of the crystals was diminished. The presence of stable Ce4+ and defects imposed by Mg2+ ions codoping were proved by absorption, photoluminescence, and scintillation decay time analysis. Hence, Mg2+ codoping resulted in quenching of the Ce3+ luminescence, acceleration of scintillation response, reduction of light yield, and thermally stimulated luminescence. The mechanism explaining a strong luminescence quenching with increasing Mg2+ ions concentration was proposed. [ABSTRACT FROM AUTHOR]