lids are prepared by compacting nanopartieles, Synthesized by the Coprecipitation method, under different pressures. The varitions of structure and interface states of the NiFe2O4 nanosolids with compacting pressures are studied by x-ray diffraction and electronic spin resonance (ESR). It is found that the crystal structure of the nanosolids has not changed under pressure up. to 6.0 GPa. but the linewidth and δ-factor values of their ESR spectra increased significantly with increasing pressure up to 45Gpa and then decreased slightly with further increase of pressure These variations are discussed in terms of the changes of interparticle magnetic dipole interaction and superexchange interaction in NiFe2O4 nanosolids under different pressures. The experimental resules. suggest that 45 Gpa is the optimum forming pressure. under which the NiFe2O4 narioparticles can be compacted into a dense solid with their structure and nanoproperues still preseyed.

Crystallization processes of an amorphous (Fe0.99. Mo0.01)78 Si9B13 alloy induced by mechanical milling and annealing at pressures from O to 7.0 Gpa were studicd. It is found that the milling time needed for the crystallization of the amorphous alloy and its crystallization products are related to the milling intensity. The crystallization products are an α-Fe(Mo, Si) disordered solid solution at a lower milling intensty. while at a higher milling intensity they aare α-Fe(Mo, Si), Fe-Si-B. and Fe2B phases. BY comparing the mechanical crystallization of the amorphous alloy with its high pressure crystallization. it is suggested that crystallization of the amorphous alloy driven by ball milling results from the simultaneous action of local pressure (4-6 Gpa) and local tempterature (600-700K), which are produced by the collision of steel balls. The local pressure decreases the thermodynamic potential barrier of nuclecleation and inereases the diffusion activation energy in the processof mechanical crystallization, Leding to that crystallization of amoirphous alloy is depressed when the crystallization needs a long-rane atomic diffusion and is promoted when the crystallization needs atomie diffusionless or short-range diffusion. The local temperature plays the same role in the mechanical crystallization as the annealing temperature in the thermal crystallization.

By using series expressions of space-dependent electrical field in a periodic composite. Which are obtained by a simple Fourer approach. The frequency dependeoce of the effective third-order nonlinear susceptibility xe of the metal-insulator composites with simple cubic arrays of coated spheres has beea exactly calculated. The results show that the frequency-dependent nonlidear response of the composites has two sharp peaks when the metal phase forms a shell structure. The strengths of the peaks are very sensitive to the relaxation time of the metal. The dependences of both the shapes and strengths of the peaks on the rakii of the cores of the coated spheres are also studied.

With the single crystals of diamond without boron as starting materials and then by adding boron atoms to their surface aggregate crystals of diamond have been synthesized under high pressure. By the analytical methods of mokifie particle-tracking autoradiography and use of an ion microprobe, the microstructure of the boron-atom distribution in thaggregate crystal of diamond has been directly observed to test and verify the distrbution model of boron atoms. The reasor why the oxidation resistance and the chemical inertia for the aggrgate crystals of diamond containing boron are excellent ar explained.

By using the decoupling aproximation and a series expression of the effective dielectric function ε., the frequency-dependent cubic nonlinear susceptibility X., of metal-insulator composites with periodic structure was strdied. The results show that if the nonlinear metal phase is in the form of coating on the linear insulator core particles. the nonlinear frequency response o the composite has one sharp peak near the surface plasmon response frequcncy of the metal. and. an enhancement of x. of several orders of magnitude can be produced. The result s also show that the nonlinear response of the composite is sensitive to the relaxation time of the metal and the dielectric constant of the linear insulator.

The double-rare-earth oxides La EuO3, NdEuO3, and SmEuO3, were synthesiszed by a high-pressure and high-temperature method. The analyses of x-ray diffraction show that LaEuO3 is of A-type (hexagonal) structure, and that PrEuO3, NdEuO3, and SmEuO3, are of B-type (monoclinic)structure, and CeEuO3.5 is of F-type (fluorite) structure. M

The samples of CeTbO3+δsynthesized by high pressure and high temperature method were studied by XPS. It was found that Tb4+ ion began to transform to Tb3+ at about 600℃ and Ce4+ to Ce3+ about 800℃. Single phase compound of CeTO3+δ having fluorite structure was formed at 1000℃, and in the compoutnd the Ce ions had been in mixed valence state. Existence of Ce3+ ions in compounds could be detected with the shift of the 888 eV peak and the change of relative intensity of it to the 882 eV peak. The duration stability of CeTbO3+δsynthesized by high pressure and temperature method was investigayted.

In the present paper the double rare-earth oxide solid solutions (EuR)O3 (R=Gd, Dy, Ho. Er, Yb, Lu) are synthesized for the first time with a combination of high pressure and high tempera-ture (3.0 Gpa and 1080-1250℃). The analysis of x-ray diffraction shows that all products are B type (monoclinic) structures of single phase. Considering η=0 the 151Eu, Mössbauer spectra were fitted by twelve transition lined. It is shown that the isomer shift depends on the unit-cell volume V1/3 in a linear fashion.

Solid solutions Ce1-xRExO2-δ (RE=Eu, Tb) were prepared by a high-temperature and -pressure method. The products were characterized by Xray diffraction (XRD), TG. Electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS), and Mossbauer spectroscopy. XRD data analysis showed that all solid solutions crystallized In a single phase cubic fluorite structure. The nonlinear relationships between the lattice parameter and dopant content for both series of solutions were ascribed to the results of cation substitutions and variations of the relative content of oxygen vacancy Vo and defect associations {RE'oceVo} and {Ce'ceVo}. EPR and XPS measurements confirmed the presence of Ce3+ ions in the sogd solutions. For the solid solutions Ce1-xEuxO2-δ, alI Eu ions were determined to be trivalent by XPS and 151Eu Mossbauer measurements. For the solutions Ce1-xTbxO2-δ. all Tb ions were also stabilized in the trivalent state. This result is different from that of the counterpart by hydrothermal conditions, in which a mixed valence of Tb3+/Tb4+ prevails at a higher dopant content. The prepared solutions Cel+xTbxO2-δ were metastable. With increasing temperature, they would he destabilized and decompose into two fluorite phases, accompanied by partial oxidation from Tb3+ to Tb4+. Alternating current impedance spectroscopy showed primarily bulk conduction for all samples. For the solutions Ce1-xEuxO2-δ. the temperature dependence of the ionic conductivity was linear within the temperature range measured with activation energies of 1.05. 0.82, and 0.87 for x=0.2, 0.38. and 0.5, respectively. For the decomposition product of the solid solution Ce0.71 Tb0.29O2-δ. the conductivity gave two linear regions with smaller activation energies; i.e., the activation energy was 0.60 eV below 600℃ and 0.39 eV above 600℃. The higher ionic conductivity (1.1xl02S/cmat720℃) for the decomposition phases of the solution Ce0.71Tb0.29O2-δ was ascribed to an electronic component involved in relation to the presence of the mixed valence of Tb3+/Tb4+ and Ce3+/Ce4+.