Jury
Dr. Matias Velazquez, CNRS délégation Alpes, Thesis Director
Dr. Christine Guéneau, CEA centre de Paris-Saclay, Reviewer
Dr. Pascal Loiseau, Chimie ParisTech - Université PSL, Reviewer
Pr. Fiqiri Hodaj, Grenoble INP - UGA, President of the Jury
Dr. Guillaume Deffrennes, CNRS délégation Alpes, Invited
Dr. Ioana Nuta, CNRS délégation Alpes, Invited
Abstract
Thanks to their thermal stability, excellent optical properties, and ability to incorporate large amounts of 100Mo, Li2MoO4 single crystals are highly promising materials for the next-generation cryogenic detectors searching for neutrinoless double-beta decays. However, radioactive trace impurities (U, Th, K) generate background noise that limits the detector’s performance. This PhD work focuses on potassium and aims to develop an integrated thermodynamic database for the Li-K-Mo-O system to guide strategies for its removal. We combined experimental synthesis, calorimetric measurements and advanced ab initio calculations with CALPHAD modeling to build a consistent description of solid, liquid, and gaseous phases, providing temperature-dependent thermodynamic properties for key compounds to support process simulations. DFT calculations suggested a possible but very low solubility limit of potassium in Li2MoO4, which experiments confirmed to be between 100 and 1000 ppm through EPMA-WDS analyses. Based on our optimized database, thermodynamic simulations predict that gas phase distillation of Li2MoO4 under an inert atmosphere can selectively volatilize potassium at high concentration ranges. Coupling these vapor phase data with validated solid–liquid equilibrium descriptions yield temperature-dependent distillation profiles that allow quantitative prediction of potassium removal rates. This approach offers a promising strategy to lower residual potassium to levels compatible with the ultra-low background requirements of future rare-event particle physics experiments.
Date infos
Tuesday, October 21 at 9:00 a.m.
Location infos
Amphithéâtre Besson, Campus Phelma, 351 Rue de la Chimie, 38400 Saint Martin d'Hères