A new single-crystal scintillator intended for applications in a scanning electron microscope (SEM) is presented. It is a single-crystal disc of yttrium aluminium perovskite activated by trivalent cerium free of traces of Fe ions. The single crystals of YAI(h : Ce 3 + (YAP: Ce 3 +) were prepared by the Czochralski method in a reducing atmosphere of Ar and Hz with an excess amount of y3 + ions. Effective methods of purification and purity control of the raw material are described. The highest achievable concentration of Ce3+ ions in as grown crystals amounted to 0.3 wt%, concentration in the melt was 8-9 times higher. The best properties were found with samples of the maximum possible concentration of Ce 3 +. Compared with the previous aluminate Y3AIs012: Ce3+ (YAG: Ce3+) these samples showed higher efficiency, a shorter decay time of luminescence (40 ns) and an emission band in a more advantageous spectral region (378 nm). Because of high resistance to radiation damage, high chemical resistance and applicability to ultra-high vacuum it is also suitable for detection of other kinds of ionizing radiation.
Spectroscopic properties of untloped YAG and YAP grown under rediicing protective attilosphere were coinpared. Blue (with F centre) or brown (with 0-centre) varieties both of t h e inaterials were p r o p r e d in t h e dependence of t h e Al,O,:Y,O, ratio in t h e melt. Colour intensity depends on the H,O : H, ratio in t h o protective atmosphere and on t h e s i p of electrical potential above t h e melt luvel.Tho coloration limy he easily reunoved by an annealing at > 1200-1400 "C. All t h e irregularities of the colourations or their reinowing b>-annealing iriay lie attributed t o t h e presence of iinpurities. E s werdcn spektroskopische Eigenschaften der undotiertcn i i n d unter retluziereiitlcr Atmosphiire geziichteten YAG und Y A P verglichen. Blaue (mit F-Zentren) odrr Iiraiine (rnit O--Zentreri) Varietiiten der heiden Materialien wurtlen in Abhiingigkoit volt1Alto, :Y,O,-Verhiiltriis i n der Schniclze gewonneri. Die I n t e n s i t i t der Fiirbung hiingt voiii H,O : H,-Vcrhiiltnis in der Schutxatinosphiire untl voiii Sinn tles elektr-ischeii Potcntials iilier der Sc:hinelzc al).Din Fiirbring karin iiian leicht bei einer Teitiperung h i > 1200-1400 'C entferrierr. Die Al~weichutigen tier Fiirbung oder der Fml)iinderring bei Temperlung inuW iinan allein tlcr Ariwcsrnkicit, von Verrinreinigringeri zuschreihrn.
Abstract. The recent development of ambient noise tomography, in combination with the increasing number of permanent seismic stations and dense networks of temporary stations operated during passive seismic experiments, provides a unique opportunity to build the first high-resolution 3-D shear wave velocity (vS) model of the entire crust of the Bohemian Massif (BM). This paper provides a regional-scale model of velocity distribution in the BM crust. The velocity model with a cell size of 22 km is built using a conventional two-step inversion approach from Rayleigh wave group velocity dispersion curves measured at more than 400 stations. The shear velocities within the upper crust of the BM are ∼0.2 km s−1 higher than those in its surroundings. The highest crustal velocities appear in its southern part, the Moldanubian unit. The Cadomian part of the region has a thinner crust, whereas the crust assembled, or tectonically transformed in the Variscan period, is thicker. The sharp Moho discontinuity preserves traces of its dynamic development expressed in remnants of Variscan subductions imprinted in bands of crustal thickening. A significant feature of the presented model is the velocity-drop interface (VDI) modelled in the lower part of the crust. We explain this feature by the anisotropic fabric of the lower crust, which is characterised as vertical transverse isotropy with the low velocity being the symmetry axis. The VDI is often interrupted around the boundaries of the crustal units, usually above locally increased velocities in the lowermost crust. Due to the north-west–south-east shortening of the crust and the late-Variscan strike-slip movements along the north-east–south-west oriented sutures preserved in the BM lithosphere, the anisotropic fabric of the lower crust was partly or fully erased along the boundaries of original microplates. These weakened zones accompanied by a velocity increase above the Moho (which indicate an emplacement of mantle rocks into the lower crust) can represent channels through which portions of subducted and later molten rocks have percolated upwards providing magma to subsequently form granitoid plutons.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.