A layered hybrid rare-earth double perovskite with two continuous reversible phase transitions induced by unusual two driving gears of fan-like rotation movements

Abstract

Organic–inorganic hybrid rare-earth double perovskite has been paid more and more attention owing to its intriguing chemical and physical properties. In this paper, we report a new layered 2D hybrid rare-earth double perovskite (HQ)₄KEu(NO₃)₈ (1, Q = quinuclidine), consisting of staggered layers of corner-sharing K(NO₃)₆ and Eu(NO₃)₆ octahedra, alternating with bilayers of the organic cations. Compound 1 could undergo two continuous reversible phase transitions induced by two driving gears of fan-like rotation movements of NO₃⁻ around Eu (261 K) and K atoms (291 K), respectively. A peak-like and a step-like dielectric anomaly were successively found corresponding to the phase transitions. In addition to the distinctive double dielectric response, compound 1 could exhibit the characteristic emission peaks of Eu³⁺ ions with a lifetime of 4.78 ms and an absolute quantum yield (QY) of 42.89%. This finding of a hybrid rare-earth double perovskite displaying two continuous reversible phase transitions and photoluminescence is expected to be utilized in designing multifunctional smart stimuli-responsive materials.