Characterization and Anticounterfeiting Applications of Low-Entropy Chloride Vacancy-Ordered Double Perovskites

Low-entropy Cs2[SnZr]Cl6, Cs2[SnHf]Cl6, Cs2[ZrHf]Cl6, and Cs2[SnZrHf]Cl6 vacancy-ordered double perovskite crystals have been synthesized through reprecipitation and hydrothermal methods. The hydrothermal method yields better-quality perovskites than the reprecipitation method. Raman spectroscopy cannot accurately characterize the local environments created by different cations occupying the same crystallographic site, which is essential for understanding and optimizing the properties of low-entropy perovskites. Solid-state NMR spectroscopy effectively clarifies the composition homogeneity at the atomic resolution in these materials. Solid-state NMR provides atomic-level insights into these promising materials.