Bridging the Salt-Inclusion and Open-Framework Structures: The Case of Acentric Ag4B4O7X2 (X = Br, I) Borate Halides

Ag4B7O12X (X = Cl, Br, I) Heptaborate Family: Comprehensive Crystal Chemistry, Thermal Stability Trends, Topology, and Vibrational Anharmonicity

Using glass crystallization and solid-state techniques, we were able to complete the family of salt-inclusion silver halide borates, Ag₄B₇O₁₂X, by the X = Cl and I members. The new compounds are characterized by differential scanning calorimetry, single-crystal and high-temperature powder X-ray diffraction, optical spectroscopy, and density functional theory calculations. In all structures, the silver atoms exhibit strong anharmonicity of thermal vibrations, which could be modeled using Gram-Charlier expansion, and its asymmetry was characterized by the skewness vector. The topology of the silver halide and borate sublattices has been analyzed separately for the first time. Along the I → Br → Cl series, we observe a decrease of the melting point and configuration entropy and an increase of thermal expansion and its anisotropy and thermal vibration anharmonicity, which indicates decreasing stability.

Where the extraordinaries meet: a cascade of isosymmetrical superionic phase transitions and negative thermal expansion in a novel silver salt-inclusion borate halide

A new silver iodide borate, Ag3B6O10I, is presented as a promising solid-state electrolyte with a δ ↔ γ ↔ β ↔ α cascade of the isosymmetric superionic phase transitions.

Incorporation of iodine into uranium oxyhydroxide phases

Herein, we have synthesised a novel uranium oxyhydroxide (UOH) phase, Rb₂K₂[(UO₂)₆O₄(OH)₆]·(IO₃)₂, under hydrothermal conditions which intercalates IO₃^-via a hybrid salt-inclusion and host-guest mechanism. The mechanism is based on favorable intermolecular bonding between disordered Rb⁺/K⁺ and IO₃^- ions and hydroxyl and layer void positions respectively. To examine whether the intercalation may occur ubiquitously for UOH phases, the known UOH mineral phases metaschoepite ([(UO₂)₈O₂(OH)₁₂]·12H₂O), compreignacite (K₂[(UO₂)₆O₄(OH)₆]·7H₂O) and also related β-UO₂(OH)₂ were synthesised and exposed to aqueous I^- and IO₃^- for 1 month statically at RT and 60 °C in air and the solid analysed using laser ablation inductively coupled plasma mass spectroscopy. Measurements indicate intercalation can occur homogeneously, but the affinity is dependent upon the structure of the UOH phases and temperature, where higher temperatures and when the interlayer space is free of initial moieties are favoured. It was also found that after repeated washing of the UOH samples with DI water the intercalated iodine was retained. UOH phases are known to form during the oxidative corrosion of spent nuclear fuel during an accident scenario in the near field, this work suggests they may help retard the transport of radiolytic iodine into the environment during a long-term release event.

Ba2B7O12F with novel FBB [B7O16F] and deep-ultraviolet cut-off edge

A new fluorooxoborate Ba₂B₇O₁₂F features novel FBB [B₇O₁₆F] and two different sizes of channels in its anionic structure, which possesses a deep-ultraviolet cutoff edge of 180 nm and a large bandgap of 6.67 eV.

New germanate and mixed cobalt germanate salt inclusion materials: [(Rb6F)(Rb4F)][Ge14O32] and [(Rb6F)(Rb3.1Co0.9F0.96)][Co3.8Ge10.2O30F2]

Single crystal growth of new germanate salt inclusion materials. [(Rb₆F)(Rb₄F)][Ge₁₄O₃₂] exhibits room temperature luminescence and [(Rb₆F)(Rb_3.1Co_0.9F_0.96)][Co_3.8Ge_10.2O₃₀F₂] demonstrates Co/Ge mixing and an unanticipated Rb/Co inclusion.