The phase diagram of the water-hydrogen system in the crystallization field of solid solutions based on ices Ih and II at high pressures

The decomposition curves of the solid solutions based on ices Ih (-solutions) and II (-solutions) in the water-hydrogen system were studied by the DTA technique at pressures up to 7 kbar. The -solution is destabilized by pressure but to a lesser degree than ice Ih and is stable up to 2.3 kbar. The-solution is stabilized by pressure and at 7 kbar decomposes at about 20°C. TheP, T-phase diagram of the water-hydrogen system in the crystallization range is constructed on the basis of reference [1] and our data. All possible types of stoichiometric interrelationships in the guest —host system are demonstrated by the example of the water-hydrogen system.     

Structural and physical properties evolution of BaIr1−xMnxO3 solid solutions synthesized by high-pressure sintering

The BaIr_1−xMn_xO₃ (0.0≤x≤1.0) solid solutions were synthesized by using the solid-state chemical method and high pressure sintering in the pressure range 0-5 GPa. According to the pressure-composition “phase diagram” at 1000 °C, the 9M BaIr_1−xMn_xO₃ transforms to the 6M form at 5 GPa and x≤1/6. In the x range 0.5-1.0, it transforms to the 9R form in a large pressure range. For the 9M BaIrO₃, the Mn ions substitution for Ir ions enhances the semiconducting property, and reduces the weak ferromagnetism. When x is larger than 1/3, the 9M/9R BaIr_1−xMn_xO₃ behave spin-glass-like state at low temperature, with the glass transition temperature T_g about 60 K. For the 6M BaIrO₃, the Mn ions doping results in that it transforms to insulator and spin-glass-like magnetism from the initial paramagnetic metal.     

The influence of P/As substitution in the melilite‐like Na2Co(P2–xAsx)O7 (x = 0.40 and 0.93) solid solutions

To investigate the influence of P/As substitution on structures and electrical properties, e.g. the effect on material densities, two new solid P/As‐doped solutions, Na₂CoP_1.60As_0.40O₇ (disodium cobalt diphosphorus arsenic heptaoxide) and Na₂CoP_1.07As_0.93O₇ (disodium cobalt phosphorus arsenic heptaoxide), with melilite‐like structures have been synthesized by solid‐state reactions. Their unit‐cell parameters are in agreement with Vegard's law. The obtained structural models were investigated by the bond valence sum (BVS) and charge distribution (CHARDI) validation tools and, for the latter, the structures are described as being built on anion‐centred polyhedra. The frameworks can be described as layered and formed by {[Co(P,As)₂O₇]²⁻}_∞ slabs, with alkali cations sandwiched between the layers and with the interlayer spaces increased due to P/As substitution. The BVS model was extended to a preliminary simulation of the sodium conduction properties in the studied structural type and suggests that the most probable sodium conduction pathways are bidimensional, at the (002) planes.