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Herein, a ternary system of TeO2–ZnO–Na2O (TZN) with competitive roles of covalent Zn–O and ionic Na–O bonds in tellurite glassy network is examined for high‐temperature in situ X‐ray diffraction (XRD) and Raman spectroscopy. TZN glasses are doped with Nd2O3 and the effects of Nd doping on the crystallization of glasses are also written. In situ high‐temperature XRD permits the assignment of each of the differential scanning calorimetry (DSC) crystallization peaks (the first crystallization peak (Tc1) is related to sodium‐based crystalline phases, while the second crystallization peak (Tc2) is correlated with tellurium‐/zinc‐based crystalline phases). The study of in situ high‐temperature Raman spectroscopy shows that Tc1 shows γ‐TeO2 crystallized phase‐like peaks while Tc2 crystallization has more α‐TeO2‐crystallized phase‐like peaks. Comparison at the same temperature (430 °C) permits a first understanding of the structural changes of the glasses in terms of the evolution first to α‐TeO2, ZnO, ZnTeO3, and Zn2Te3O8 crystalline phases compared with Na10Zn4O9 phase. The ZnTeO3 and Zn2Te3O8 crystallization evolution is also compared between the Nd‐doped and nondoped glasses, which gives more insight into the tellurite glass structures. [ABSTRACT FROM AUTHOR]

First‐principles molecular dynamics calculations are performed to investigate the reactions of hydrogen and calcium carbonate melts at pressure–temperature conditions appropriate to the Earth's lower mantle and core–mantle boundary. Two models with different hydrogen‐to‐carbonate ratios are studied. A variety of chemical reactions are observed. It is found that hydrogen dissociates readily and reacts with free carbonate anions forming various transient chemical species and water molecules. Further reactions of these reactive species serve as intermediates to form C–C and C–O connections. The unreacted bulk carbonates are linked via polymeric‐cornered shared CO4 tetrahedra. At 110 GPa and 4087 K, "diamondoids" with tetrahedral C4 moieties are found. The theoretical results support recent reports on the observation of tetrahedra CO4 in high‐pressure carbonate glasses and suggest a plausible explanation of ice VII inclusion in deep‐Earth diamonds. [ABSTRACT FROM AUTHOR]

Due to its advantageous thermophysical qualities, U3Si2 piques the interest of the nuclear industry as an accident‐tolerant fuel to replace uranium dioxide (UO2). Herein, the structural, electrical, thermodynamic, and transport features of the U3Si2 compound are investigated using the full‐potential linearized augmented plane wave approach within the density functional theory, and within the generalized gradient approximation related to spin orbit and Hubbard. The ground statistic parameters that are estimated, such as the lattice constants and bulk moduli, are qualitatively consistent with previous experimental and theoretical evidence. The density of states analysis reveals that U3Si2 is a metal complex. In addition, the macroscopic thermal effects of U3Si2 are calculated using the quasi‐harmonic Debye model, which includes lattice vibrations. Experimental and theoretical findings are compared with the calculated variations in volume, heat capacity, entropy, and Debye temperature as a function of temperature in the range of 0–1500 K. Some thermal properties are projected to be pressure dependent in the range of 0–20 GPa. In the temperature range of 0–1500 K, the semiclassical Boltzmann transport equation is utilized to estimate electron transport parameters such as the Seebeck coefficient, thermal and electrical conductivity. [ABSTRACT FROM AUTHOR]

The dielectric properties of CuCrO2 bulk and thin films are studied by evaluating the complex dielectric function ε. In addition to the small peak near the Néel temperature TN, a secondary broad peak is found at high temperatures around Tm=450 K≫TN. As a feature of relaxor ferroelectrics, the maximum temperature Tm increases with increasing frequency. The real part of ε decreases with increasing magnetic field h and the peak at TN vanishes. The secondary peak becomes smaller and is broadened with increasing magnetic field. ε increases with increasing film thickness. Near Tm, the dielectric function offers a critical behavior expressed by an exponent γ=1.74. Using scaling arguments, critical exponents β=0.13 and δ=13.38 are deduced. The exponents depend on the film thickness. While β increases, the exponent γ is reduced with increasing film thickness. [ABSTRACT FROM AUTHOR]

The microstructural evolution of postirradiation annealing (PIA) and reirradiation in high‐dose proton‐irradiated Fe–Cu model alloys (Cu: 0.05 and 0.1 wt%) at high temperature (about ≈290 °C) is investigated using positron annihilation and nanoindentation. The positron results show that vacancy defects and Cu precipitates are produced in high‐dose proton‐irradiated Fe–Cu alloys. Under PIA at 500 °C, vacancy defects are recovered substantially, whereas Cu precipitates still remain in Fe–Cu alloys. After reirradiation, the S parameter in the damaged region evidently increases when compared with the postirradiation annealed samples. It is suggested that Cu precipitates remain in the postirradiation annealed samples that strongly affect the formation and growth of vacancy defects. More defects are produced in reirradiated samples, resulting in higher S parameters. The nanoindentation results show obvious hardening in the reirradiated samples. Both vacancy defects and Cu precipitates lead to the hardening of high‐dose proton‐irradiated Fe–Cu model alloys. [ABSTRACT FROM AUTHOR]