The crystal growth of ortho- and pyrosilicates from W and Mo crucibles

Abstract

The feasibility to grow bulk La-GPS:Ce scintillation crystals by the Czochralski method using Mo crucibles has been reported.

Characterization of LaGPS:Ce scintillation crystals obtained under a reducing atmosphere

“…The absolute light yield of sample 3 reached 24100 ph./MeV with an energy resolution of 10 % (Table 2). This value remarkably lower than the best values of the light yield described in the literature [32] but coincided with that presented in our previous work [11]. On the other hand, energy resolution almost doubled in comparison to [11], which indicates the improved quality of the crystals obtained in this work.…”

“…In our case, there are no structured Ce 3+ peaks due to a relatively large Ce 3+ concentration and a very high optical density of Ce 3+ in this range, just wide bands in the 270-350 nm and <250 nm both at absorption and excitation spectra. The same spectral shape was observed in many earlier studies, see, for example [11,31]. The photoluminescence spectrum (Figure 3b) contains a typical luminescence bands peaked at 367 nm and 390 nm associated with the transition to 2 F5/2 and 2 F7/2 terms of the split ground state of Ce 3+ ions [29] excited in the UV-band.…”

“…The crystal diameter was 15 mm and the length of the boule was 90 mm. The upper part of the ingot was polycrystalline, while lower part was single crystalline, transparent, and mainly free from visible gas inclusions and surface etching, which were observed in the previous study [11]. This was attributed to the reduced impact of the CO-containing growth atmosphere.…”

“…The problem of Ir crucibles substitution with Mo or W crucibles is successfully solved for rare earth aluminates, such as rare earth garnets and perovskites by applying reducing atmosphere conditions in Czochralski or Bridgman processes. A transfer of these technologies to rare earth silicate growth is complicated due to interaction between SiO2 and CO gas formed in the growth atmosphere due to interaction graphite heat insulation with residual oxygen [11]. In the previous study of our group [11] we demonstrated the possibility of obtaining Ce-doped crystals of yttrium oxyorthosilicate and lanthanum gadolinium pyrosilicate from W/Mo crucibles by controlling atmosphere composition and modifying the crystallizer.…”

Composition-Engineered GSAG Garnet: Single-Crystal Host for Fast Scintillators

“…Nowadays, the price of Ir has even increased several times with no trace of a trend reversal in sight. This is reflected in the higher interest for Mo and W crucible technologies in the community. − It was shown that, in general, the ions constituting a crucible material can penetrate into the crystal. , In some cases (e.g., when using the Mo crucible), it can even improve the scintillation characteristics . In the case of GAGG, the effect of codoping of CZ-grown single crystals by W and Mo had been recently studied − and was found to be rather complex.…”