Synthesis of High Entropy Lanthanide Oxysulfides via the Thermolysis of a Molecular Precursor Cocktail

High entropy (HE) materials have received significant attention in recent years, due to their intrinsically high levels of configurational entropy. While there has been significant work exploring HE alloys and oxides, new families of HE materials are still being revealed. In this work we present the synthesis of a novel family of HE materials based on lanthanide oxysulfides. Here, we implement lanthanide dithiocarbamates as versatile precursors that can be mixed at the molecular scale prior to thermolysis in order to produce the high entropy oxysulfide. The target of our synthesis is the HE Ln₂SO₂ phase, where Ln = Pr, Nd, Gd, Dy, Er and where Ln = Pr, Nd, Gd, Dy for 5 and 4 lanthanide samples, respectively. We confirmed the structure of samples produced by powder X-ray diffraction, electron microscopy, and high-resolution energy dispersive X-ray spectroscopy. Optical spectroscopy shows a broad emission feature centered around 450 nm as well as a peak in absorption at around 280 nm. From this data we calculate the band gap and Urbach energies of the materials produced.