Actual Phase Diagram Research Articles

Tunable pyroelectricity, depolarization temperature and energy harvesting density in Pb(Lu0.5Nb0.5)O3-xPbTiO3 ceramics

The ferroelectric to antiferroelectric (FE-AFE) phase boundary design based on orthorhombic AFE phase and tetragonal FE phase is an effective method to develop high-performance pyroelectric materials due to the complete release of large electrical polarization in FE-AFE phase transition. Herein, we report the phase structure evolution in (1-x)Pb(Lu0.5Nb0.5)O3-xPbTiO3 (abbreviated as PLNT100x) ceramic system based on the relationship of tolerance factors versus electronegativity differences. The composition/temperature effects on FE-AFE phase transition behavior, pyroelectricity, depolarization temperature (Td) and energy harvesting performance were investigated systematically. Obviously, PLNT system displays superior pyroelectric characteristics as well as high Td. The maximum pyroelectric peak was 4.50 μC·cm−2·K − 1 over a wide temperature range from 28 °C to 167 °C. In addition, the obtained maximum pyroelectric energy harvesting density was 1.66 J/cm3 which was much higher than the currently reported values, indicating a potential candidate for pyroelectric energy conversion applications. Based on the modified Ginzburg−Landau−Devonshire (GLD) phenomenology, the composition/temperature driven phase transitions were discussed, and the temperature−electric field (T − E) phase diagram was accordance with actual phase diagram based on the experimental data.

Uncertainties in the Periodic Solution of a Truly Non-linear Oscillator Differential Equation Using MDTM

A periodic solution is obtained for a truly nonlinear oscillator differential equation and the corresponding energy relation using the modified differential transform method (MDTM). Unlike the method of harmonic balance with lower order harmonics, the MDTM provides the same approximate solution for these two nonlinear oscillator differential equations. The phase diagram generated from the approximate solution differs appreciably when compared to the actual phase diagram. Improvements proposed earlier by the present authors in the MDTM are partially successful in bridging the gap between the approximate and actual phase diagrams. Several researchers have claimed the MDTM as an efficient semi-analytical method. However, the present study cautions its usage on the truly nonlinear oscillator differential equations.

Universal Intermediate Phases and Nanostructures of High-Temperature Superconductors

The phase diagrams of cuprate superconductors are frequently oversimplified and represented by a cartoon in which Tc(x) is parabolic. It is then supposed, at least in many theories, that a single continuous metal–insulator transition occurs near the optimal composition x = xc, where Tc is maximized. In fact, the actual phase diagrams are not parabolic, but are described, even in the simplest case (LSCO), better by a trapezoid, with two phase transitions, not one. Because of strong electron–phonon interactions, the two transitions are broadened and obscured by spinodal immiscibility gaps. Examples of such gaps show how they can be identified and related to the formation of nanodomains and filaments.

Convection and Crystallization in a Liquid Cooled from above: an Experimental and Theoretical Study

a buoyant liquid becomes non-turbulent or even ceases upon loss of Evidence from experiments and theoretical modeling suggests that the superheat. Transferring these results to magmatic systems, we systems crystallizing exclusively from the top down and rejecting a suggest that the dynamics inside intrusive bodies upon cooling are buoyant liquid effectively cease convecting once the initial superheat very sensitive to the actual phase diagram, the kinetics of cryshas been lost. We report here on a combined experimental and tallization and the density relation between crystals and melt. theoretical study designed to investigate in some detail the interaction of convection and crystallization in a fluid cooled from above. The experiments are carried out in a small tank where temperature, composition, mush thickness, and convective velocities have been monitored. After an initial period of turbulent convection removing

Comment on “One-Dimensional Disordered Bosonic Hubbard Model: A Density-Matrix Renormalization Group Study”

We present the phase diagram of the system obtained by continuous-time worldline Monte Carlo simulations, and demonstrate that the actual phase diagram is in sharp contrast with that found in Phys. Rev. Lett., 76 (1996) 2937.

The primary test of measuring system for the actual emittance of relativistic electron beams

Abstract Recently, a novel system has been established in Tsinghua University, P.R. China. The system is able to measure the actual phase diagram of a relativistic electron beam (4–10 MeV). The system is mainly composed of a magnetic scanning system, a slit, a fluorescent screen and a CCD camera. After the assembling and testing of the system, as well as the composing of software of the image process, the actual emittance of the 4 MeV electron beam, which is from the standing wave linac in Accelerator Lab, is measured by this system and RMS. Emittance is also achieved. Lastly, the measurement error is analyzed and the overall performance is presented: the system error is 10%–20%, the scope of measurement is 0.4–350 mm mrad. Experiments show that the magnet scanning method is applicable and the system is preliminary practicable.

On the interpretation of the phase diagram of La2−xMxCuO4

The difference between the phase diagrams of La2−x(Ba,Sr)xCuO4 and Nd2−xCexCuO4 is discussed. It is proposed that the discrepancy of x-values corresponding to the transition from antiferromagnetic dielectric state to conducting one (respectively, x≈0.06 in La2−x(Ba,Sr)xCuO4 and x≈0.125 in Nd2−xCexCuO4) results from non-homogeneous doping of La2−x(Ba,Sr)xCuO4 over the range 0.06<x<0.125, when localized holes are added to each second CuO2 layer. Therefore the actual phase diagram of the “holedoped” superconductor La2−x(Ba,Sr)xCuO4 coincides with one for the “electron-doped” superconductor Nd2−xCexCuO4. It is shown that all features observed in La2−x(Ba,Sr)xCuO4 around x=0.125 are clarified on this basis.

The influence of solution-model complexity on phase diagram prediction

In the derivation of phase diagrams using solid- and liquid-solution thermodynamic equilibria, thermodynamic models are used to extrapolate experimental data to a broader range of compositions and temperatures. Such models have historically increased in complexity from the regular-solution formalism, with regard to both temperature and composition dependence of parameters. The regular, quasi-regular, subsubregular, and quasi-subsubregular models have been applied to existing thermodynamic data for four“simple” metallic systems of differing types (Cu-Ni, Pb-Ag, Sn-Zn, and Ge-Mg) to illustrate the effect of more accurate thermodynamic modeling on the resulting predicted phase diagrams. Comparison with the actual phase diagrams demonstrates the relative importance of“nonregularity” in the solution with regard to both composition and temperature in the accuracy of phase diagram prediction.

Phase Change of the Indium Rich Alloys

The stability of a f.c.c. phase and two f.c.t. phases, one has the axial ratio more than unity and the other less than unity, of In–Cd, In–Sn, In–Hg and In–Pb are discussed. On the basis of the nearly free electron model, the internal energies for these phases are calculated. The phase which has the least internal energy in any electron/atom region can actually exist. The calculated regions of these phases agree comparatively well with the actual phase diagram. A reasonable explanation on the change in the transport properties at the phase boundaries is also given by the model.