The influence of rare-earth ions on the low-temperature thermoluminescence of Bi₄Ge₃O₁₂

Abstract

Low-temperature (20-290 K) thermoluminescence spectra of Bi4 Ge3 O12 reveal a range of trapping levels, some of which are common to both undoped and doped material. The emission spectra for undoped and transition-metal-doped Bi4 Ge3 O12 indicate that at low temperatures, intrinsic luminescence centres result in broad-band emission typical of signals from relaxed excitons or possibly excited bismuth ions. For material containing rare-earth ions, the signals are characteristic of the rare-earth dopants, even when the rare-earth ions are present in concentrations as low as 3 ppm. The temperatures of the glow peaks seen at ~54, 105 and 141 K for undoped material are strongly modified by the rare-earth ions. The trapping and recombination sites, monitored by rare-earth emission, are intimately linked, probably within large complex structures. For these three glow peaks the peak temperature varies smoothly with the ionic radii of the rare-earth impurities. These movements are substantial, with changes of up to 50 K, as a function of the rare-earth radii. Of all the rare-earth ions, europium forms the most stable recombination centres. This is probably because the trivalent europium ion is similar in size to the host (bismuth) ion for which it substitutes. Tentative models for trapping sites and thermoluminescence mechanisms are proposed.

Complex oxide scintillators: Material defects and scintillation performance

“…Such effects lower the capacity of the PbWO 4 lattice to trap and store generated charge carriers after X-or γ-irradiation. Consistently, the faster scintillation and photoluminescence decays are obtained [49,56], transmission [50,57] and especially radiation resistance [52,58] characteristics are noticeably improved, see Fig. 4.…”

“…This may mean that the thermally destroyed dipoles at this temperature can contain both the spatially correlated electron and hole trap creating thus a kind of complex defect. Such kind of defects has been considered in explaining the TSL characteristics of different compounds [49,50]. It is worth noting that TSL emission spectra of the peaks at ~50 K, 190 K and 320 K show maxima at different energies (inset of Fig.…”

Ion size effects on thermoluminescence of terbium and europium doped magnesium orthosilicate

“…Thus, we prefer a more general model 20,[23][24][25][26][27] in which there is a close association of the trap and emission center. Such packages are not unexpected as the rare earth ions differ in valence from the host ions and also differ in size.…”

Characterization of Bi4Ge3O12 single crystal by impedance spectroscopy

“…Bismuth germanate (Bi 4 Ge 3 O 12 -BGO), which has a cubic crystalline structure known as eulitine, has been demanded a great deal of interest due to its electro-optic, electro-mechanical and scintillator properties [1][2][3] . In particular, the use of BGO single crystals in electromagnetic measurements presents many advantages, since it possesses small temperature-dependence of electro-optic effect, high electrical resistivity, no optical activity, no natural birefringence and no pyroelectric effects 2,4 .…”