In-situ ultrasonic calibrations of pressure and temperature in a hinge-type double-stage cubic large volume press

Here,simultaneous in-situ calibration of pressures and temperatures was performed in a hinge-type second-stage cubic large volume press(LVP)up to 15 GPa and 1400 K by an acoustic travel-time approach.Based on the recently reported P-tSand P-T-tP-tSequations for Al2O3buffer rod,the cell pressures and temperatures in the chamber of LVP were insitu determined,in comparison with those by conventional off-line(or fixed-points)pressure calibration method and direct thermocouple measurement,respectively.It is found that the cell pressures of the LVP chamber are significantly reduced after annealing at simultaneous high pressures and high temperatures,owing to the stress relaxation as accumulate in the LVP chamber.This acoustic travel-time method is verified to be a good way for precise determination of thermal(cell)pressures at high temperature conditions,and is of great importance and necessity to conduct in-situ physical property measurements under extreme high P-T conditions,especially when the precious synchrotron x-ray/neutron diffraction beams are not available.

Pressure-induced disordering of site occupation in iron–nickel nitrides

Controlled disordering of substitutional and interstitial site occupation at high pressure can lead to important changes in the structural and physical properties of iron–nickel nitrides.Despite important progress that has been achieved,structural characterization of ternary Fe–Ni–N compounds remains an open problem owing to the considerable technical challenges faced by current synthetic and structural approaches for fabrication of bulk ternary nitrides.Here,iron–nickel nitride samples are synthesized as spherical-like bulk materials through a novel highpressure solid-state metathesis reaction.By employing a wide array of techniques,namely,neutron powder diffraction,Rietveld refinement methods combined with synchrotron radiation angle-dispersive x-ray diffraction,scanning electron microscopy/energy dispersive x-ray spectroscopy,and transmission electron microscopy,we demonstrate that high-temperature and high-pressure confinement conditions favor substitutional and interstitial site disordering in ternary iron–nickel nitrides.In addition,the effects of interstitial nitrogen atoms and disorderly substituted nickel atoms on the elastic properties of the materials are discussed.

Manipulating metal-insulator transitions of VO_(2) films via embedding Ag nanonet arrays

Manipulating metal-insulator transitions in strongly correlated materials is of great importance in condensed matter physics,with implications for both fundamental science and technology.Vanadium dioxide(VO_(2)),as an ideal model system,is metallic at high temperatures and shown a typical metal-insulator structural phase transition at 341 K from rutile structure to monoclinic structure.This behavior has been absorbed tons of attention for years.However,how to control this phase transition is still challenging and little studied.Here we demonstrated that to control the Ag nanonet arrays(NAs)in monoclinic VO_(2)(M)could be effective to adjust this metal-insulator transition.With the increase of Ag NAs volume fraction by reducing the template spheres size,the transition temperature(Tc)decreased from 68°C to 51°C.The mechanism of Tc decrease was revealed as:the carrier density increases through the increase of Ag NAs volume fraction,and more free electrons injected into the VO_(2)films induced greater absorption energy at the internal nanometal-semiconductor junction.These results supply a new strategy to control the metal-insulator transitions in VO_(2),which must be instructive for the other strongly correlated materials and important for applications.