Growth of 2 Inch Eu-doped SrI2 single crystals for scintillator applications

Abstract

A vertical Bridgman (VB) crystal growth process was established using modified micropulling-down (μ-PD) crystal growth system with a removable chamber that was developed for the growth of deliquescent halide single crystals because conventional μ-PD method does not allow growth of large bulk single crystals. Eu:SrI 2 crystals were grown from the melt of (Sr 0.98 Eu 0.02 )I 2 composition using carbon crucibles. Undoped μ-PD SrI 2 crystals were used as seeds that were affixed to the bottom of the crucible. All the preparations preceding the growths and the hot zone assembling were performed in a glove box with Ar gas. Then the removable chamber was taken out of the glove box, attached to the μ-PD system, connected with a Turbo Molecular pump, and evacuated down to 10 -4 Pa at ~300°C. After the baking procedure, high purity Ar gas (6N) was injected into the chamber. The crucible was heated by a high frequency induction coil up to the melting point of Eu:SrI 2 . After melting the starting materials, the crucible was displaced in downward direction for the crystal growth and then cooled down to room temperature. Thus, 2 inch and crack-free Eu:SrI 2 bulk crystals were produced. The crystals had high transparency and did not contain any visible inclusions.The crystals were cut and polished in the glove box and then sealed in an aluminum container with an optical window for characterization. The details of the crystal growth are discussed.

Advanced Halide Scintillators: From the Bulk to Nano

“…Even though SrI 2 :Eu was patented by Hofstadter, [51] it regained the interest of the scientific community at the beginning of the last decade due to technological advancements that allowed large-volume high-quality single-crystal growth of this highperformance scintillator. In the last decade, the R&D of SrI 2 was focused on the improvement of its properties via codoping, [66,175,176] optimizing the growth conditions, [65,103,177,178] and packaging. [179] Moreover, Yb 2þ doping was also suggested as prospective due to the faster scintillation kinetics.…”

Growth and Scintillation Properties of Two-Inch-Diameter SrI2(Eu) Single Crystals

“…A considerable reduction in the volume of gas was achieved using two main procedures. First, a repeated melting process was used according to the temperature schedule applied in the crucible to decrease bubble formation in the SrI 2 (Eu) crystals . Second, a forced exhaust system was designed and installed in the VB μ-PD apparatus.…”

“…First, a repeated melting process was used according to the temperature schedule applied in the crucible to decrease bubble formation in the SrI 2 (Eu) crystals. 11 Second, a forced exhaust system was designed and installed in the VB μ-PD apparatus. This exhaust system operated during the melting stage to generate conditions for bubble-free crystal formation.…”

“…As a rule, SrI 2 (Eu) scintillating crystals have been grown via the vertical Bridgman (VB) method using a quartz ampule. Alternatively, a crystal growth apparatus equipped with a removable chamber has been developed for the growth of bulk single crystals with large diameters. − In the near future, further development of this equipment and the corresponding glovebox is expected to satisfy the requirements for growing large-diameter halide crystals.…”

Microstructure and Mechanical Properties of Platinum Fiber Fabricated by Unidirectional Solidification

“…On the other hand, inorganic single crystals have been manufactured by melt-growth approaches such as the Czochralski (Cz) [2,3], Vertical Bridgman (VB) [4,5], and micro-pulling-down (µ-PD) methods [6][7][8][9][10][11][12][13][14]. In particular, the µ-PD method is suitable for the material research of single crystals because it has a faster growth rate than other conventional melt-growth methods [6][7][8][9].…”