Experimental and numerical investigations of the Czochralski growth of Li2MoO4 crystals for heat- scintillation cryogenic bolometers

C. Stelian (1) , M. Velazquez (1) , Philippe Veber (2) , A Ahmine (1) , T. Duffar (1) , P. de Marcillac (3) , A. Giuliani (3) , D. Poda (3) , S. Marnieros (3) , C. Nones (4) , V. Novati (3) , E. Olivieri (3) , A. Zolotarova (3) , H Cabane (5) , T Redon (3)

1 SIMaP - Science et Ingénierie des Matériaux et Procédés
2 iLM - LUMINESCENCE - iLM - Luminescence
3 CSNSM - Centre de Sciences Nucléaires et de Sciences de la Matière
4 IRFU - Institut de Recherches sur les lois Fondamentales de l'Univers
5 CristalInnov

A new technology for the mass production of lithium molybdate (Li2MoO4) crystals needed for the realization of the cryogenic neutrinoless double-beta decay detectors is under development within the framework of the CLYMENE project. Crystals with 4 and 5 cm in diameter were grown in two different Czochralski configurations. The first configuration, based on inductive heating of a RF coil coupled with a platinum crucible, was used to grow crystals of 4 cm in diameter. Bolometric tests performed with two samples cut from a 230 g crystal have shown less performances of the large sample (158 g), which had a cleavage, as compared to the small non-cracked sample (13.5 g). Numerical 2 modeling was applied to investigate the temperature field in the furnace, the melt convection and thermo-elastic stresses in the crystal. Numerical results reveal 30% higher thermal stress at the bottom part of the ingot in the case of a concave shape of the crystal tail (experimental case) as compared to the case of a convex shaped tail. This could explain why the fracture started at the bottom part of the 230 g crystal boule, and highlights the importance of the crystal shape in the last stage of growth process. The furnace configuration used to grow 5 cm-diameter crystals was numerically optimized in order to reduce the thermal stress in the crystals. The first kg-mass Li2MoO4 ingot grown in the optimized configuration exhibit regular shape and good structural quality.

Mots clés: B1 Lithium compounds; A2 Czochralski method; B1 Oxides; B2 Scintillator materials; A1 Computer simulation

Domaines: Matériaux

C. Stelian, M. Velazquez, Philippe Veber, A Ahmine, T. Duffar, et al.. Experimental and numerical investigations of the Czochralski growth of Li2MoO4 crystals for heat- scintillation cryogenic bolometers. Journal of Crystal Growth, 2020, 531, pp.125385. ⟨10.1016/j.jcrysgro.2019.125385⟩. ⟨hal-02395850⟩