Bulk Crystal Growth and Single-Crystal-to-Single-Crystal Phase Transitions in the Averievite CsClCu5V2O10

Quasi-two-dimensional averievites with triangle-Kagome-triangle trilayers are of interest due to their rich structural and magnetic transitions and strong spin frustration that are expected to host a quantum spin liquid ground state with suitable substitution or doping. Herein, we report the growth of bulk single crystals of averievite CsClCu₅V₂O₁₀ with dimensions of several millimeters on the edge in order to (1) address the open question of whether the room-temperature crystal structure is P3̅ m1, P3̅, or P2₁/c or else, (2) to elucidate the nature of phase transitions, and (3) to study direction-dependent physical properties. Single-crystal-to-single-crystal structural transitions at ∼305 and ∼127 K were observed in the averievite CsClCu₅V₂O₁₀ single crystals. The nature of the transition at ∼305 K, which was reported as a P3̅ m1-P2₁/c transition, was found to be a structural transition from high-temperature P3̅ m1 to low-temperature P3̅ by combining variable-temperature synchrotron X-ray single crystal and high-resolution powder diffraction. In-plane and out-of-plane magnetic susceptibility and heat capacity measurements confirm a first-order transition at 305 K, a structural transition at 127 K, and an antiferromagnetic transition at 24 K. These averievites are thus ideal model systems for a deeper understanding of structural transitions and magnetism.