Y(BD4)3, an efficient store of deuterium, and impact of isotope effects on its thermal decomposition

Graphical abstract: Display Omitted Highlights: ► Y(BH4)3, novel D-rich borodeuteride with possible nuclear fission applications. ► Study of isotope effects of the H→D substitution on its physicochemical properties. ► Small isotope effect for the temperature of thermal decomposition. ► Anomalous large effect for the heat at the 1st stage of thermal decomposition. - Abstract: Y(BD4)3, which stores as much as 16.6 wt.% and 252 kg/m3 D, has been synthesized via high-energy disk milling. The thermal decomposition of Y(BD4)3 has been investigated using thermogravimetric and calorimetric analyses combined with the spectroscopic evolved gas analysis. Two major endothermic events corresponding to thermal decomposition could be distinguished in the DSC profile up to 400 °C at ca. 231 and 285 °C, preceded by a phase transition (at ca. 198 °C) from the low-temperature Pa-3 form to a high-temperature polymorph of Y(BD4)3 (F-43c). The high-temperature phase forming at the onset of thermal decomposition may be prepared quantitatively by heating of the low-temperature phase to ca. 216 °C followed by rapid quenching. Effects of isotope H→D substitution on various properties of yttrium borohydride have been analyzed. Y(BD4)3 constitutes a very efficient low-temperature source of deuterium gas on the laboratory scale.