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Tungsten-bronze type titanate BaNd2Ti4O12 ceramics were synthesized by solid state reactions. The conductivity and microwave dielectric loss of the samples that were thermally treated under various conditions and Ta-doped were investigated by electrochemical impedance measurement and microwave dielectric resonator measurement. The variation in conductivity with annealing atmospheres of air, O2, and N2 was consistent with the defect equilibriums 2O × O ↔2V •• O +O2↑+2eʹ and Ti × Ti +eʹ↔TiʹTi, suggesting n-type conductance for BaNd2Ti4O12. Thermal treatment in air/O2 was found to favor the elimination of the native defects V × O, TiʹTi and weakly bound electrons thus decreasing the conductivity. Thermal treatment in a N2 atmosphere, which had a low oxygen partial pressure, increased the defect content and the conductivity. Thermal treatment in air/O2/N2 did not clearly affect the microwave dielectric loss, suggesting that native [Article] www.whxb.pku.edu.cn

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： APdcatalystsupportedbysingle鄄walledcarbonnanotubes(SWNTs)waspreparedbyaredoxreaction betweenSWNTsandPdCl 2 solution.Thesupportedcatalystwascharacterizedbytransmissionelectronmicroscopy (TEM),X 鄄 raydiffraction(XRD),X 鄄 rayphotoelectronspectroscopy(XPS)andthermo鄄gravimetric(TG)techniques. ResultsshowedthatlargequantitiesofPdparticleswithdiametersofca2nmdistributedevenlyonthesurfaceof SWNTsandthecontentofPdwas14.13%(w,massfraction)whenusingSWNTsand12mmol •L-1 PdCl 2 asreactants. Thesupportedcatalyst,afterreductionbyH 2 ,exhibitedhighcatalyticactivityinSuzukireaction.Theyieldofbiphenyl was98.10%after30minreactionat90 益.

A series of oxides in the Mn3O4-Fe2O3 system have been synthesized at 1200°C in air, followed by quenching to room temperature. Three solid solutions, Mn3-3xFe3xO4 (0.00£x£0.278), Mn3-3xFe3xO4(0.291£ x£0.667), and Mn2-2xFe2xO3 (0.89£x£1.00), have been identified by powder X-ray diffraction (XRD). Rietveld refinement of the XRD data show that the solids belong to the hausmannite phase with the space group I41/ amd, the spinel phase with the space group Fd3m, and the hematite phase with the space group R3c, respectively. Between these are two-phase regions. 57 Fe Mössbauer spectra indicate that the valence state of Fe in the three solid solutions is +3; in addition, there are two crystallographically independent Fe 3 + ions in the unit cells of the hausmannite and spinel phases, and one Fe 3+ in the hematite phase. Analyses of 57 Fe Mössbauer spectra and X-ray photoelectron spectra (XPS) revealed that a formula of Mn 2+ 1-xFex 3+ [Mnx 2+ Fe 3+ x Mn 3+ 2-3x] O4 describes the cation distribution of both the hausmannite and spinel phases, but that for the hematite [Article] www.whxb.pku.edu.cn