Unveiling the structural changes of an Eu(III) thermal hystory phosphor juxtaposing high-resolution and high-energy powder X-ray diffraction

Materials enabling luminescence-based high-sensitivity assessment of an object thermal history are relevant in key applicative fields. In this context, we reported [Eu(BTC)(H2O)6] (Eu-1, H3BTC = 1,3,5-benzenetricarboxylic acid) [Adv. Funct. Mater. 2024, 2313045]. Its progressive dehydration (343-423 K), triggering a phase transition, alters the shape of the Eu(III) ions emission spectrum and the depopulation kinetics of their 5D0 level, making Eu-1 a multiparametric thermal history phosphor (THP) with record relative sensitivity in ratiometric and decay kinetics modes (11.3 and 1.8%/K). HR- and HE-PXRD, in situ heating Eu-1 in the range 303-423 K, will disclose the structural changes underneath the observed performance, from both a periodic (HR-PXRD plus “classical” structural analyses) and a local perspective (HE-PXRD plus total scattering analyses). The outcomes will help rationalize the behaviour of Eu-1 and engineer new-generation THPs based on Eu(III) coordination polymers.