Formation of luminescence centres under excitation with electron beams in PbWO ₄ and ZnWO ₄ crystals

Abstract

PACS 78.55.Hx, 78.90+t The leading edge of intrinsic luminescence pulse in PbWO 4 and ZnWO 4 single crystals is studied. The rise of luminescence intensity is observed after excitation with electron beam pulse. The luminescence rise is shown to be a result of luminescence center formation via electron-hole recombination within spatially correlated pairs. An electron of a geminate electron-hole pair of PbWO 4 crystal self-traps and stimulates self-trapping of a hole at a close distance. In the ZnWO 4 crystal a hole of a geminate electron-hole pair self-traps and stimulates self-trapping of the electron producing a W 5+ center at a short distance. The risetime of luminescence depends on spatial separation of recombining components. It is short even at 80 K (100 ns in PbWO 4 and 10 ns in ZnWO 4 ). The reasons for different rise time and different spatial distribution of electron and hole self-trapped centers are discussed.

Phase Transformation of Lead Tungstate at Normal Temperature from Tetragonal Structure to Monoclinic Structure

“…Even small changes in these conditions induce considerable changes of emission spectra . The “blue luminescence” is usually originated from a regular WO 4 2− complex anion, whereas the discussion about the “green luminescence” still remains controversial …”

Presence of excited electronic state in CaWO4 crystals provoked by a tetrahedral distortion: An experimental and theoretical investigation

“…Therefore, for AWO 4 scheelite, the material properties can be primarily associated to the cluster constituents, and the disparity or mismatch of both clusters can induce structural order-disorder effects, which will significantly influence the luminescence properties of the scheelites-type tungstates. [14][15][16] This structural pattern is a characteristic key for all the AWO 4 scheelites.…”

Surfactant-Assisted Hydrothermal Synthesis, Physical Characterization, and Photoluminescence of PbWO4

“…It is one of the most challenging issues to control the particle sizes, morphologies, and structures of inorganic crystals for which the physical properties of micro- and nanocrystals can be significantly determined by their dimensions, crystallinity, size, morphology, and geometry. − Recently, micro- and nanostructured tungstate compounds, such as ZnWO 4 , , CaWO 4 , Bi 2 WO 6 , BaWO 4 , PbWO 4 , FeWO 4 , etc., have aroused much interest because of their luminescent behavior, structural properties, and potential applications. Tungstate crystals belong to the so-called self-activated scintillator family, and their intrinsic luminescence are due to radiative annihilation of self-trapped excitons localized on the regular WO 4 or WO 6 units for sheelite or wolframite crystals, respectively. − As an important scintillating crystal, lead tungstate (PbWO 4 ) has attracted great attention in high-energy physics due to its high density (8.3 g/cm 3 ), fast decay time (less than 10 ns for the most part of light output), high irradiation damage resistance, interesting excitonic luminescence, thermoluminescence, and stimulated Raman scatting behavior . PbWO 4 exists in nature as tetragonal stolzite with scheelite-type structure.…”

“…Tungstate crystals belong to the so-called self-activated scintillator family, and their intrinsic luminescence are due to radiative annihilation of self-trapped excitons localized on the regular WO 4 or WO 6 units for sheelite or wolframite crystals, respectively. [15][16][17] As an important scintillating crystal, lead tungstate (PbWO 4 ) has attracted great attention in high-energy physics due to its high density (8.3 g/cm 3 ), fast decay time (less than 10 ns for the most part of light output), high irradiation damage resistance, interesting excitonic luminescence, thermoluminescence, and stimulated Raman scatting behavior. 18 PbWO 4 exists in nature as tetragonal stolzite with scheelite-type structure.…”