RECrO3 as High-Contrast Thermochromic Memory Pigments: Enabled by Hydrothermal Distortions and Magnetic Tuning (RE = Eu, Tb, Y)

Inorganic crystals synthesized via different methods with the "same" composition often exhibit distinct properties, a phenomenon frequently overlooked or misinterpreted. In this work, we demonstrate the peculiar magnetic properties and thermochromic memory behavior of three perovskite-structure rare-earth chromites (RECrO3, RE = Eu, Tb, and Y) synthesized by a mineralizer-assisted hydrothermal method at 225 °C. The crystals feature an elongated b-axis and greater distortion of the CrO6 octahedral subunits. Crystal shapes are sensitive to the composition, mineralizer concentration, and reaction temperature. Raman and infrared peaks show a RE3+-dependent behavior. All samples are canted-antiferromagnetic with significantly lower Néel temperatures than the samples synthesized via other methods. Three notable magnetic transition points are shown in TbCrO3, which have never been found in other samples. Temperature and magnetic field dependent magnetization curves of EuCrO3 samples show crystal shape dependent magnetic behaviors. All of the samples show continuously irreversible thermochromic properties from 100 to 500 °C with color changes from yellowish green to reddish brown with the highest chromaticity aberration of ΔE = 51.47 in TbCrO3. This work indicates that the materials synthesized via the mineralizer-assisted hydrothermal crystallization method facilitate versatile tunability of the structure and physical properties with promising thermal recording applications.