Contact Melting in Simple Eutectic System

The growth of the liquid interlayer in the system lead-tin at 463 K is studied experimentally in the nonstationary diffusion process of contact melting. The contact melting was carried out between pure tin and solid solution of tin in lead (0, 5.9, 11.5, 17.8, 24.8 mol. % Sn). The results indicate that the concentration range of the liquid interlayer corresponds to the interval of homogeneity of the liquid phase in the phase diagram at the experiments temperature. It is shown that the solid solution corresponding to the solidus near the liquid/crystal interface can not be generated by the diffusion of atoms from the liquid into the crystal. An explanation is offered that the solid solution of solidus composition at the liquid/crystal interface occurs as a result of the precipitate from the metastable (supersaturated by lead) melt

Effects of Cr Doping and Water Content on the Crystal Structure Transitions of Ba2In2O5

Temperature dependent crystal structure alterations in the brownmillerite type material Ba2In2O5 play a fundamental role in its applications i photocatalytic CO2 conversion; ii oxygen transport membranes; and iii proton conduction. This is connected to a reversible uptake of up an equimolar amount of water. In this study, in situ X ray and neutron diffraction were combined with Raman spectroscopy and solid state nuclear magnetic resonance experiments to unravel the effects of Cr doping and water content on the crystal structure transitions of Ba2In2O5 H2O x over a wide temperature range 10 K lt; T lt; 1573 K, x lt; 1 . A mixture of isolated and correlated protons was identified, leading to a highly dynamic situation for the protons. Hence, localisation of the protons by diffraction techniques was not possible. Cr doping led to an overall higher degree of disorder and stabilisation of the tetragonal polymorph, even at 10 K. In contrast, a further disordering at high temperatures, leading to a cubic polymorph, was found at 1123 K. Cr doping in Ba2In2O5 resulted in severe structural changes and provides a powerful way to adjust its physical properties to the respective applicatio

Chemically Controllable Magnetic Transition Temperature and Magneto-Elastic Coupling in MnZnSb Compounds

International audienceMagneto-caloric materials offer the possibility to design environmentally friendlier thermal management devices compared to the widely used gas-based systems. The challenges to develop this solid-state based technology lie in the difficulty of finding materials presenting a large magneto-caloric effect over a broad temperature span together with suitable secondary appli-cation parameters such as low heat capacity and high thermal conductivity. A series of compounds derived from the PbFCl structure is investigated using a combination of computational and experimental methods focusing on the change of cell volume in magnetic and non-magnetic ground states. Scaling analysis of the magnetic properties determines that they are second order phase transition ferromagnets and that the magnetic entropy change is driven by the coupling of magneto-elastic strain in the square-net through the magnetic transition determined from neutron and synchrotron X-ray diffraction. The primary and secondary application related properties are measured experimentally, and the c/a parameter is identified as an accurate proxy to control the magnetic transition. Chemical substitution on the square-net affords tuning of the Curie temperature over a broad temperature span between 252 and 322 K. A predictive machine learning model for the c/aparameter is developed to guide future exploratory synthesis