Manganese agglomeration and radiation damage in doped Li₂B₄O₇

Manganese clustering effects were studied in Li₂B₄O₇ (LTB) ceramics. The samples LTB:Me + Mn (Me = Sn, Cu, Mn, Zn, Be) were prepared by a two-stage doping method (except for LTB doped with Mn solely). EPR, pulsed cathodoluminescence, thermoluminescence (TL) were measured. Mn clustering causes supralinearity of the material response to the radiation dose, reversible shift of the dosimetric TL peak, and irreversible radiation damage. Radiation damage of the LTB crystal lattice is accompanied with the formation of a peroxide bridge instead of a single oxygen at the common vertex of two BO₄ tetrahedra. Repelled by an excessive positive charge of a Mn cluster, holes are localized around at traps including the peroxide bridges where they are stable up to 630 K. The extent of the radiation damage can be estimated by the intensity of the high-temperature TL at 630 K, when the released holes recombine with the electrons near regular Mn²⁺. The most stable against the radiation damage and also suitable for TL dosimetry is LTB:Sn + Mn.