Polycrystalline samples with nominal composition of Ba(Fe 1-x Ir x ) 2 As 2 (x=0. 10, 0.15, and 0.20) were investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), electrical resistivity, and magnetization measurements. XRD and SEM results showed that almost single phase samples were obtained. Bulk superconductivity with T C~2 8 K was observed in the x=0.10 sample. T C~2 8 K is the highest superconducting critical temperature among the reported data for electron-doped AFe 2 As 2 -type (A=Ca, Sr, and Ba) superconductors. The upper critical field H c2 (0) reaches as high as 65 T for the x=0.10 sample. The underlying physics is discussed in connection with Co-doping case.PACS numbers: 74.70. Dd, 74.25.Fy, 74.62.Dh, 74.62.Bf * Corresponding author. Tel.: +86-10-6251-1523.E-mail address: tszhao@ruc.edu.cn (T.-S. Zhao).-1 -Since the recent discovery of superconductivity in the F-doped RFeAsO (R = La, Ce, Pr, Nd, Sm, and Gd ) and Th-doped GdFeAsO with the highest T C up to as high as 55-56 K [1-6], the FeAs-based superconductors have attracted much attention. Another family of oxygen-free FeAs-based compounds with the ThCr 2 Si 2 -type structure such as K or Na-doped AFe 2 As 2 (A = Ca, Sr, Ba, and Eu) and Co-doped AFe 2 As 2 (A = Sr, Ba) were found to be superconductors with the highest T C up to 38 K [7][8][9][10][11][12][13]. The electron-doped Ba(Fe, Co) 2 As 2 system has been extensively studied and the temperature-composition phase diagram of this system has been determined by several groups [14][15][16][17][18][19][20][21]. The determined phase diagrams show a striking feature that there is a coexistence of antiferromagnetisim and superconductivity in an underdoped region. Very recently, a number of electron-doped Ba (Fe, M) 2 As 2 (M = Ni, Ru, Rh, and Pd) [22][23][24][25] and Sr(Fe, M) 2 As 2 (M = Ni, Ru, Rh, Pd, and Ir) [26][27][28][29] compounds was also found to exhibit superconductivity.Among the electron-doped superconductors, a higher T C was observed in Co-doped BaFe Powder X-ray diffraction (XRD) using Cu K α radiation at room temperature was used to identify phase structure of the samples. Figure 1(a) shows the powder XRD patterns for Table I. It can be seen from Table I that the a-axis increases and the c-axis shrinks slightly with increasing the Ir content x, respectively.We have examined the microstructure and phase composition of the samples using a scanning electron microscope (SEM) (LEO 1450, Carl Zeiss SMT Ltd., Cambridge, UK) equipped with an energy dispersive X-ray (EDX) spectrometer. SEM micrographs show that, comparing with the undoped BaFe 2 As 2 , there is a gradual and considerable decrease in the grain size for the Ir-doped samples with increasing the Ir content. Figures 1(b) and 1(c) show the backscattered electron images for the samples with x = 0.10 and 0.20, respectively. It can be seen that there exists a small fraction of white phase as an impurity phase in the samples. Our EDX analysis shows that the white phase is IrAs 2 phase. In fact, a small pe...

Abstract. Studies on the formation of the ancient Diexi barrier lake on the Mingjiang River, southwestern China, have long been carried out. However, investigations into the correlation between the palaeoclimate and palaeoenvironment and the palaeoseismic events in this area are rarely found in literature. The present study took sediments from the ancient Diexi barrier lake to investigate the palaeoclimate, palaeoenvironment and palaeoseismic events. A drilling at the centre of the barrier lake was conducted and the core of about 260 m long was examined. The palaeoclimate and palaeoenvironment indicators (sporopollen, carbon and oxygen isotopes, organic matter, calcium carbonate, granularity) from the sediments have been tested and analysed, and indicate that there were 10 climatic and environmental periods between 30 000 and 15 000 a BP (before present). The discovered disturbance segments in the core indicate there were at least 10 seismic events during that period. The consistency between climate change and seismic events indicates that a strong seismicity is normally accompanied by a climatic variation. This may be a useful supplement for climate and geohazard predictions in the future.