Zhao Muyu

XPS study of adsorbed oxygen of nanocrystalline LaFeO3 materials

Abstract The adsorbed oxygen and lattice oxygen of nanocrystalline LaFeO 3 materials have been studied by X-ray photoelectron spectroscopy at room temperature and under a compacting pressure of 0.0 and 1.0 GPa. It was found that the signal of the chemisorbed oxygen was less intense than that of the lattice oxygen at 0.0 GPa, but larger than that of the lattice oxygen at 1.0 GPa for an average crystal size larger than 15 nm. When the average crystal size was 2.0 nm, the chemisorbed/lattice oxygen ratio did not significantly change between 0.0 and 1.0 GPa.

The theorem of corresponding relation between neighboring phase regions and their boundaries in phase diagrams (I)

Abstract Several fundamental concepts in phase diagrams have been discussed. The theorem of corresponding relation between the number of different phases in the neighboring phase regions Φ and the dimension R 1 of their phase boundary in the phase diagrams is derived from the phase rule. The five corollaries of this theorem for isobaric phase diagrams are derived also. By applying this theorem and its corollaries, the following results can be obtained. Both the boundary rule and contact rule of phase regions in phase diagrams may be deduced. The ten empirical rules for constructing the complex ternary isobaric phase diagrams from phase diagram units may be put on a theoretical basis. The relation between neighboring phase regions and their boundary in phase diagrams of one-, two-, three- and four-components of all types and in the different horizontal and vertical sections of ternary phase diagrams may be explained without introducing any supplementary concept.

Synthetic studies of nanocrystalline composite oxides with the perovskite structure based on LaFeO3

Abstract The precursors for synthesis of nanocrystalline composite oxides La1−xSrxFe1−yCoyO3 (x = 0.2, 0.4; y = 0.5, 0.6) were prepared using the polyethylene glycol and citrate methods. After the solid-phase reaction at 550°C for 2 h, the mean diameters of the nanocrystalline grains were about 15 nm. The results indicate that the effects of the solid-phase reaction depend on the distribution of various components in the precursor and the conditions of preparing them. The polyethylene glycol method is superior in many respects to the citrate method.

The calculation of P-T-X phase diagrams of CdSn, CdZn and SnZn binary alloy systems

Abstract The P-T-X phase diagrams of CdSn, CdZn and SnZn binary alloy systems were calculated. The results of the calculation agree well with the experimental data, so our method is acceptable.

Ferroelectric Phase Transition in Nanocrystalline Lead Zirconatitanate System by Raman Scattering

The Raman spectra of PbZr0.3Ti0.7O3 for different grain size as well as at high temperature and high pressure have revealed that its structure is transformed from tetragonal to quasi-cubic phase with decreasing grain size. The phase transition temperature drops down to a lower temperature and the pressure-induced phase transition can be correlated with the diffuse phase transition.

Excess molar volumes of lead-based α-phase solid solutions in (lead + bismuth + indium) at 298.15 K

Abstract Excess molar volumes VmE of lead-based α-phase solid solutions in (lead + bismuth + indium) at 298.15 K are reported. The experimental results are fitted using the sub-regular solution model. It is shown that bismuth contributes negative deviations and indium positive deviations to VmE, which are related to the relative volumes of the pure metals and are attributed to the different interactions between different solute and solvent atoms. The volume effect of solutes in the solid solutions is consistent with the thermodynamic trend of solutes in the liquid alloys.

Calculation of high pressure phase diagrams of binary alloy systems

Abstract High pressure phase diagrams of the Cd-Pb binary alloy system were calculated. The results not only tested the reliability of experimental values but also improved on the reported calculations.

EPR spectra of nanocrystalline composite oxide LaFeO3 with the perovskite structure

Abstract Nanocrystals of LaFeO3 with mean grain diameters of 12.4, 12.6, 14.4, 16.0 and 16.3 nm were compacted into pellets under static pressure of 0.5, 1.0 and 1.5 GPa in the axial direction at room temperature. Their EPR spectra change with grain sizes and compacted pressures. The results show that the g values increase a little with the increment of compacted pressures, whereas the peak intensities of EPR spectra of nanocrystalline materials are about 103 times as strong as those of conventional materials. This paper discusses characteristics of EPR spectra of nanocrystalline composite oxide LaFeO3.

Influence of grain size on the soft mode and the phase transition in the nanocrystalline PbTi1−xZrxO3 system

Abstract The Raman spectra of nanocrystalline PbTi 0.75 Zr 0.25 O 3 show that its perovskite phase occurred at a higher crystallization temperature during its sol-gel process than the perovskite PbTiO 3 phase. The effects of grain size on the ferroelectric phase transition and the soft mode have been investigated. The phase transition temperature T c is shifted to a lower temperature with decreasing grain size. The possibility that the additional mode occurring in the low frequency Raman spectra might be due to zone boundary transverse acoustical phonons which couple to the q ∼ 0 soft TO phonon mode is confirmed. The Raman spectra, as a function of pressure, reveal that the phase transition may be correlated with Diffuse Phase Transition (DPT).

Calculation of thermodynamic properties and phase diagrams of the CdPbSn ternary system

Abstract Using known binary phase diagram data, the thermodynamic properties of the solid-solution phase in three binary systems, necessary for the prediction of the CdPbSn ternary data, are estimated using a regular solution model for Sn-rich solid solutions or by applying a sub-regular solution model for Pb-rich solid solutions. The CdPbSn ternary phase diagrams are then calculated. The calculated, more complete, phase diagrams of the CdPbSn ternary system agree with our experimental results and supplement the reported calculated diagram.