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Pantala flavescens (Fabricius, 1798) is one of the most common species of dragonflies and has been found throughout from tropic to temperate zones worldwide. In this study, RNA-seq of P. flavescens was carried out through Illumina high-throughput sequencing technology. Approximately 37,868 unigenes and 47,188 transcripts were obtained. The average length of the assembled unigenes was 908.59 bp. We identified 1442 cDNA simple sequence repeats (SSRs) among the 37,868 unigenes, with 864 (59.91%) di-nucleotide repeats, 537 (37.32%) tri-nucleotide repeats, 32 (2.22%) complex-nucleotide repeats, and 9 (0.62%) with tetra-nucleotide repeats. Sixty microsatellite molecular markers were randomly selected to test amplification. Of the 60 markers, 32 (53.33%) produced clear amplicons of the expected size, 10 (16.67%) amplified nonspecific products, and 18 (30%) failed to amplify the DNA products. In order to assess their applicability, genetic diversity of the 32 SSR loci was tested in 32 individuals from Nanchang in...

The experiments of electrical resistivity and thermopower on Nd 0.75 Sr 1.25 CoO 4 film in the temperature range 90 K T

Thermopower (S), in-plane resistivity (ρ) and magnetic susceptibility (χ) on electron-doped Nd1.85Ce0.15CuO4+δ single crystals have been investigated. Susceptibility (χ) shows a kink at T m about 230 K. T m is close to the characteristic temperature T ∗ of thermopower. A positive thermopower over the whole temperature region suggests the existence of holelike carrier and the behavior of temperature dependent diffusion thermopower can be attributed to two-band model, which means the coexistence of two types of charge carriers and we abbreviate them as holelike band and electronic band in this text. When the temperature increases above T ∗ , the diffusion thermopower of holelike band contribution satisfies the Heikes formula as a narrow band does and the bandwidth t is estimated about 0.02 eV. The fitting results of resistivity in deoxygenated and oxygenated samples support the coexistence of two types of charge carriers. A kink is also observed in a derivative plot of in-plane resistivity at the temperature close to T ∗ .

Temperature dependence of the electrical resistivity (ρ) and thermopower (S) in the ab-plane of Nd0.75Sr1.25CoO4 thin films have been investigated systematically in the temperature range 70 K T 310 K . The specimen presents a p-type semiconducting transport property. The S nearly keeps constant at high temperatures and decreases at low ones with an additional step-like decrease, which was argued to be intimately related with the magnetic properties of the specimen. The resistivity follows the Arrhenius law. And the large value of the power factor suggests the films may be a good candidate for the thermoelectric material.

The transport properties of Bi2−xPbxSr2Co2Oy single crystals with various Pb contents are studied. The in-plane resistivity ρab always shows metallic behavior from room temperature (290 K) to 80 K with various Pb contents, while the out-of-plane resistivity ρc shows rather complex behavior. For Pb-free samples, ρc shows semiconductive behavior in the measured temperature range. With increasing Pb content, the temperature dependence of ρc shows an evolution from semiconductive through crossover to metallic behavior. According to the formula for ρc proposed previously, the evolution of ρc behavior is fitted well. Using the small polaron theory, the complex behavior of ρc is interpreted. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

MgB 2 /Fe wires and MgB 2 /Ta/Cu wires were prepared through the in situ powder-in-tube method by using Mg and B powders at ambient pressure. The phase compositions, microstructural features are investigated by X-ray diffraction and scanning electron microscope. The transport critical current properties are measured by the standard four-probe technique. It is found that no impurity phase is formed in MgB 2 /Fe wire. At the same time, there are almost no reaction between iron and magnesium according to the results of X-ray diffraction analyses. In addition, it is found that MgB 2 grains in Fe clad are fined by comparing the micrograph of Fe-clad wire and Ta-clad wire. The high transport critical current density ( J c ) of 6.0 × 10 4 A/cm 2 (5 K, 4 T) and 5.2 × 10 3 A/cm 2 (15 K, 6 T) are obtained in the MgB 2 /Fe wire.

Long dense MgB 2 wires were successfully fabricated through the in situ powder-in-tube method by using steel sheath with low carbon content. Short samples of MgB 2 /Fe wires were sintered at 650–850 °C for 2–5 h in argon. Critical current density ( J c ) of the wires was measured in the temperature range of 4.2–30 K in the magnetic field up to 3 T by standard four probe method. High J c values of 1.3×10 5 A/cm 2 in self-field and 7.5×10 4 A/cm 2 in 1 T at 15 K were obtained for MgB 2 /Fe wires. The microstructure observation for MgB 2 wires shows that no reaction between Fe and MgB 2 was found and MgB 2 /Fe wires have better grain connectivity and higher density than MgB 2 bulk samples. The grain connectivity in wires is better than MgB 2 bulk samples. The results indicate that the J c can be further improved to meet the requirement for applications by optimizing the process conditions.

The phase stability of intermetallics R3(Fe,T)29 with Nd3(Fe,Ti)29 structure and site preference of some 3d or 4d transition elements T were investigated in molecular static and molecular dynamic methods with a series of ab initio pair potentials obtained though the lattice inversion method. Calculated results show that adding either Cr, Mo, Ti, V or Nb atoms makes the crystal cohesive energy of R3(Fe,T)29 decrease markedly, proving that these atoms can stabilize R3(Fe,T)29 with the structure of Nd3(Fe,Ti)29, even though the R3Fe29 crystal structure is itself metastable. The calculated lattice parameters are in good agreement with the experimental data. The degree of the decrease in cohesive energy corresponds with the species and occupation sites of the ternary atoms. The order of site preference of these stabilizing elements T is 4i2, 4i1 and 4g with the occupation of 4i2 corresponding to the greatest energy decrease. The calculated result further shows that the addition of Cu or Ag cannot play a role in stabilizing the structure. These calculated results correspond well to available experiments. Supported by the pair potentials, calculated structures are stable within a certain temperature range and the space group of the final structure remains unchanged with respect to a variety of initial deformations. So it was confirmed that there exist a series of R3(Fe,T)29 compounds with the stable structure of Nd3(Fe,Ti)29 in the R–Fe–T systems. The process of the evolution from the RFe5 structure to metastable R3Fe29 was well explained too with the pair potential in this paper. All these prove the effectiveness of ab initio pair potentials obtained through the lattice inversion method in the description of rare-earth materials.

A theory of optical conductivity due to the competition between interlayer direct hopping and hopping assisted by spin fluctuations has been developed. The prediction of our theory captures the main feature of the experiment. Thus, we argue that the anomalous behavior of the c-axis optical conductivity in the underdoped cuprates may be properly understood within the theory.

We have measured the specific heat, resistance and dc susceptibility of the mixed valence manganite La 0.85 K 0.15 MnO 3 as a function of temperature. The sample shows colossal magnetoresistance effects with phase transitions at low temperature. The magnetic specific heat of this sample is proportional to the temperature coefficient of the resistance, following the Fisher-Langer relation. This suggests that the sharp drop in the transition region of the sample is due to the magnetic scattering.

Bi2Sr2Ca1-xPrxCu2Oy (x ranging from 0 to 0.5) single crystals have been grown by a self-flux method from Bi-rich melts. The crystals obtained manifest slim and plate-like shapes. The crystallinity is studied by x-ray diffraction. The x-ray θ-scanning rocking curve shows that the slim crystal has perfect crystal structure while the plate-like crystal is mosaic along the c-axis. The in-plane resistivity ρab(T) has been measured for crystals with different Pr doping levels. Tc is suppressed gradually upon doping while the residual resistivity increases strongly. A superconductor-insulator transition is observed which is attributed to the tetragonal-orthorhombic phase transition when the Pr content reaches about 0.5. The effect of oxygen doping on in-plane resistivity ρab(T) is also studied for x = 0.22 and 0.40 crystals.

Experiment on X-ray photoelectron spectroscopy of samples of Bi 2 Sr 2− x La x CaCu 2 O y has been performed to investigate the distribution of La atoms on the cation sites and the change of valence of Bi and Cu atoms. The analysis indicates that La mostly takes the place of Sr at Sr sites. An increase in the average valence of Bi and a decrease in that of Cu have been observed. The resistivity and thermoelectric power (TEP) of the samples have also been measured. The two-band model is applied to analyse the results of TEP.

Polycrystalline samples of Bi 2 Sr 2− x La x CaCu 2 O y and pure Bi2212 with different oxygen content have been prepared and studied by Raman spectroscopy. No frequency change of O Bi A g mode is observed. The O Sr A g mode exhibits remarkable downward frequency shift. The analysis indicates that the content of excess oxygen inserted into the Bi 2 O 2 layer is the important factor causing frequency shift of the O Sr A g mode.

The temperature dependences of the in-plane resistivity ab(T ) and out-of-plane resistivity c(T ) in Bi-2212 crystals covering the region from the underdoped to the overdoped regime have been measured. In the underdoped regime, ab(T ) deviates from a linear temperature dependence below a characteristic temperature T *, well above Tc, whose value decreases with increasing hole concentration. For underdoped crystals, ab(T) shows a typical S-shaped temperature dependence and ab = 0*+exp(-/T ) is satisfactorily obeyed over a much wider temperature range from slightly above Tc up to T *. Near the optimal region, the T -linear dependence of ab(T ) is maintained over a wide temperature interval. In contrast, a power law ab~Tn (n = 1.5-1.8) is followed in the overdoped regime. As regards the out-of-plane resistivity, on the other hand, c(T ) for the underdoped Bi2Sr2CaCu2Oy crystals shows a semiconductive behaviour, which is well described by the formula c = (C1/T)exp(C2/T ) + C3T + C4. The difference between the temperature dependences of c(T ) in the overdoped Bi2Sr2CaCu2Oy and Bi1.85Pb0.15Sr2CaCu2O8 + crystals, with basically the same values of Tc and nearly the same power-law temperature dependences of ab(T ) (ab~T 1.4), reveals that the inter-plane disorder in the form of oxygen vacancies and substituted cations acting as an extra blocking layer plays an important role in out-of-plane transport.

The in-plane resistivity ${\ensuremath{\rho}}_{\mathrm{ab}}(T)$ and the out-of-plane ${\ensuremath{\rho}}_{c}(T)$ have been extensively measured for the pure single-crystal ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{CaCu}}_{2}{\mathrm{O}}_{8+\mathrm{\ensuremath{\delta}}\mathrm{}}\mathrm{}(\mathrm{Bi}2212)$ annealed at different oxygen pressure. The ${\ensuremath{\rho}}_{c}(T)$ and anisotropy $[{\ensuremath{\rho}}_{c}(T)/{\ensuremath{\rho}}_{\mathrm{ab}}(T)]$ decreases rapidly with increasing carrier concentration. It is found that the out-of-plane resistivity decreases linearly with temperature down to about 120 K for the overdoped sample; its resistivity anisotropy is a weak temperature dependence. In the $\mathrm{ab}$ plane, the anisotropy is very weak and nearly independent of temperature. The data of ${\ensuremath{\rho}}_{c}(T)$ and ${\ensuremath{\rho}}_{c}(T)/{\ensuremath{\rho}}_{\mathrm{ab}}(T)$ are well fitted by the bipolaron theory proposed by Alexandrov and Mott.

The temperature dependent thermopower S a ( T ) of the Bechgaard salt (TMTSF)2PF6 was measured along the highly conducting a axis. Surprisingly, an abrupt change of gap value was found at 8 K. The gap values revealed by the thermopower measurements within the SDW phase are much smaller than that revealed in the resistivity measurement, implying the existence of magnetic-polaron hopping below T SDW .

The whiskers with 2212 phase have been grown out by annealing a melt-quenched plate in a stream of gas at for 121 hours. Temperature dependences of the magnetic susceptibility (-T) and the critical current density have been measured. The transition point of the whiskers is 76.2 K, and the value is at 63.4 K, zero magnetic field. near is found, which hints that there may exist some inner grain Josephson junctions in the whisker.

The effect of rare earth ion size on the charge transfer and Raman spectra of the rare-earth-substituted Pb-based 1212 compounds (Pb 0.65 Sr 0.35 )Sr 2 (R 0.5 Ca 0.5 )Cu 2 O y (R = Y, La, Ce, Pr, Nd, Yb, Lu) has been studied systematically. X-ray diffraction showed that all the rare-earth-substituted samples were single phase of the Pb-1212 except R = Ce. The compound with R = Ce did not form under the same synthesis conditions. Both the a and c parameters increased monotonically with the substitution of larger size rare earth. AC susceptibility measurement revealed that all the samples showed superconducting transitions between 43 and 68 K except the largest ion La-substituted sample. T c showed a tendency to decrease with rare earth radius. Raman spectra of these samples illustrated that only one peak at about 540 cm −1 appeared for all the rare-earth-substituted samples in the range of 100 to 800 cm −1 . This peak was attributed to the vibration of the apical-O(2) in this system. Its frequency showed a tendency to increase with rare earth ion. The relationship between lattice parameter, superconductivity, apical-O(2) vibrational characteristic and ionic radius were discussed in this paper. Based on several experimental facts, our present Pb-1212 samples are considered to lie in the underdoped region of the T c - n diagram.

The positron lifetime as a function of the Cd content x was measured for the as-prepared samples of (Pb1-xCdx)Sr-2(Y0.5Ca0.5)Cu2Oy. A constant long-lived Lifetime was observed for all samples. The intensity of the long-lived lifetimes has an obvious decrease starting at x = 0.3 and indicated the existence of an impurity phase in the sample with x = 0.3. The monotonous decrease of the bulk lifetime for the single-phase samples implies that Cd mainly substitutes for Pb. The changes of the microstructure with Cd content were discussed.

Samples of Bi 2 Sr 2 Ca 1− x Pr x Cu 2 O y have been characterized by resistivity and thermoelectric power measurements. All metallic samples show superconductivity with a maximum T c = 90 K at x = 0.2. The sample of x = 0.6 shows a crossover from hopping conduction at low temperature above T c to metallic conduction at high temperature. For the metallic samples below x = 0.6, the results of thermoelectric power are well fitted by both of a phenomenological band spectrum model and the Nagaosa and Lee model.

The effects of Ca substitution on the core levels and valence electronic states of Nd{sub 2{minus}x{minus}y}Ce{sub x}Ca{sub y}CuO{sub 4{minus}{delta}} have been studied using x-ray-photoelectron spectroscopy. It is found that the fraction of monovalent Cu derived from the Cu-2p spectra apparently increases with increasing Ca concentration. Ca doping leads to an enhancement in the density of states at the Fermi level for superconducting Nd{sub 1.85{minus}y}Ce{sub 0.15}Ca{sub y}CuO{sub 4{minus}{delta}}. This could arise from Ca doping making it easier to lose oxygen from the samples and lead to an increase in electron carriers. {copyright} {ital 1997} {ital The American Physical Society}

Two kinds of methods have been used to synthesize Pb 0.5 Sr 2.5 Y 0.6 Ca 0.4 Cu 2 O 7-y samples. The synthesized sample using the first method shows superconductivity, while that using the second method exhibits a localized behavior at low temperature. Thermogravimetric analysis (TGA) and electrical transport measurements have been carried out on superconducting and nonsuperconducting samples grown under the two kinds of synthesis conditions anti the effect of oxygen content on the transport and superconducting propertics is discussed briefly.

The effect of annealing conditions on the superconductivity of the Pb-based 1 2 1 2 phase Pb0.65Sr2.35Y0.5Ca0.5Cu2O y system was studied. The weight change of the samples was measured by thermogravimetric analysis (TGA). The phases occurring in the samples were detected by X-ray diffraction (XRD) and their superconducting transitions were determined by alternating current (a.c.) susceptibility measurements. The results showed that the oxygen occupancy sites of the samples annealed under various conditions were different, and the oxygen content or oxygen occupancy site affected the phase formation of the sample. It has been found that there is an optimum value of oxygen content at which TC is the highest, and the highest TC can be obtained only within a very narrow range of oxygen content.

The electronic transport properties in Bi2Sr2CuOy crystals have been investigated with the focus on the localized behaviours at low temperature. It is found that in the passage of transition from metallic to insulating states the samples first show two-dimensional weak localization behaviour, and cross over to the variable-range hopping conduction corresponding to the strong-localization regime. We analyse the experimental results and suggest that the metal-insulator transition is caused by the effects of both disorder in the lattice and electron correlations.

Cu 2p core-level spectra have been obtained on as-grown and reduced ${\mathrm{Nd}}_{1.85}$${\mathrm{Ce}}_{0.15}$${\mathrm{CuO}}_{\mathit{y}}$. The intensity ratio of the Cu 2p satellite to main peaks (${\mathit{I}}_{\mathit{s}}$/${\mathit{I}}_{\mathit{m}}$) is lower compared with the case of p-type cuprates. This characteristic is discussed on the basis of the crystal-chemical parameters. The bond valence sums (BVS) of each ion are calculated. It is found that the effective oxidation state of Cu is, in contrast to the p-type cuprate superconductors, less than 2+. The relationship among the BVS, the Madelung site potential difference \ensuremath{\delta}${\mathit{V}}_{\mathit{M}}$ between the in-plane O and Cu, and the Cu-O charge-transfer gap \ensuremath{\Delta} is discussed. It is pointed out that the relatively lower ${\mathit{I}}_{\mathit{s}}$/${\mathit{I}}_{\mathit{m}}$ of Cu 2p XPS spectra reflects the lower valence state of Cu, or relatively smaller values of \ensuremath{\Delta} as well as \ensuremath{\delta}${\mathit{V}}_{\mathit{M}}$.

Samples of nominal composition (Pb 1- x Cd x )Sr 2 (Y 0.5 Ca 0.5 )Cu 2 O y (0⩽ x ⩽0.6) synthesized at 1000°C in oxygen were investigated. All the as-prepared samples became superconducting at around 25 K, except x =0 and 0.1. For the superconducting samples, the content of Cd has little effect on T c onset . However, the same annealing at 560°C for 1 h in air which induced superconductivity in the non-superconducting “as-prepared” sample of x =0.1 led to the depression of the superconductivity of the “superconducting as-prepared” samples of 0.2⩽ x ⩽0.6. The post-treatments in air and oxygen (1 and 5 atm) substantially increase the resistivities at 300 K of the samples.

We have successfully synthesized a new family of superconductors (Sr 2− x Bi x ) (Ln 2− y Ce y )Cu 2 O 8−δ (0.3⩽ x ⩽0.5; 0.6⩽ y ⩽0.9) in which the rock-salt block (Nd,Sr)O in the (Nd 1.18 Sr 0.82 ) (Nd 1.46 Ce 0.56 )Cu 2 O 8 is replaced by (Bi,Sr)O. Its lattice parameters are a=3.82 A and c=12.66 A . This structure may be also believed to be the structure resulting from removing the Bi-O bilayers in Bi 2 Sr 2 (Nd,Ce) 2 Cu 2 O y . The maximum zero resistivity temperature was about 30 K. It is found that superconductivity takes place in a narrow range of oxygen content and the thermodynamic stability of these materials is closely related to the value of δ.

We have measured the ab-plane resistivity on a number of Bi2Sr2CuOy crystals from 4.2 K to 300 K. The as-grown crystals usually exhibit a minimum in their normal-state resistivity. The low-temperature electronic transport can be described by a hopping con

I – V characteristics of epitaxial, c-axis-oriented GdBa 2 Cu 3 O y film was measured between 70 K and 90 K. A magnetic field of 3 T was applied parallel to the basal plane (a – b plane), the angle between the field and one side of the substrate being 0° or 60°. We found that there were differences between the I – V characteristics for the 0° and 60° cases due to the anisotropy of the superconductivity in the a – b plane.

Les caracteristiques courant-tension de ces films sont dues au fluage de flux. Certaines differences dans les resultats peuvent etre dus a l'anisotropie. Ainsi ces caracteristiques peuvent etre liees a l'anisotropie des supraconducteurs a haute T c

This chapter presents a carefully designed apparatus for high precise measurement of the thermopower in the temperature range from 4–300 K. Due to the strong anisotropy and subtle balance between interchain and intrachain electronic coupling, these quasi-lD conductors exhibit a variety of electronic ground states, including SDWs, superconductivity, magnetic-field-induced spin-density waves (FISDWs), anion order-disorder transition and so on. In the ease of (TMTSF) 2 ClO 4 , which exists the anion order-disorder transition (T ao = 24 K), if quenching above Tao, its ground state is SDW state ( T SDW =6 K). The thermopower data of (TMTSF) 2 ClO 4 , at different cooling rates through T ao , are reported. The resolution of the system can reach to 0.01 μV/K. The thermopower of organic conductors (TMTSF) 2 ClO 4 single crystals were measured. A linear behavior at high temperature and a deviation at 140 K attributed to 1D—2D crossover were observed. Different cooling rates are realized to study the anion order–disorder transition in thermopower at T ao =24K. There is an obvious upturn just below T ao when the cooling rate reaches 0.3 K/s. The fastest cooling process can spot a clear trace of SDW transition at 4.5 K.

This chapter applies two kinds of measurement methods to study the systematic transport property of both Bi 2-x Pb x Sr 2 Co 2 O y single crystals with various Pb content and Bi 2 Sr 2 CaCu 2 O y single crystals with various oxygen content. Anisotropic transport property measurement in strongly layered structure material is a challenge task. A key point is to overcome problems involving non-uniform current flow in the measuring process. Bi 2-x Pb x Sr 2 Co 2 O y is a misfit-layered compound, and Co ions in the conducting CoO 2 layer form a triangular lattice instead of a rectangular one in the conducting CuO 2 layer of high-T c cuprate oxides. The completely different anisotropic transport properties are observed in both Bi 2-x Pb x Sr 2 Co 2 O y and Bi 2 Sr 2 CaCu 2 O y crystals. For Bi 2-x Pb x Sr 2 Co 2 O y crystals, the evolution of pc behavior from semiconductive through crossover to metallic behavior is interpreted by a small-polaron model. As for high-T c cuprate, there is no consensus about the origin of semiconductor behavior of ρ c (T) so far. Therefore, more systematic investigation on related layered strongly correlated metals will help to clarify this problem.

We have successfully synthesized the superconductor (Sr[sub 1.5]Bi[sub 0.5])(Y[sub 2[minus][ital x]]Ce[sub [ital x]])Cu[sub 2]O[sub 8[minus][delta]], the crystal structure of which is similar to that of [ital T][sup *]-phase (Nd,Sr,Ce)[sub 2]CuO[sub 4]. This structure is also believed to be without the double Bi-O layer as in Bi[sub 2]Sr[sub 2]([ital L],Ce)[sub 2]Cu[sub 2]O[sub [ital y]], and the coupling between layers in (Sr,Bi)[sub 2](Y,Ce)[sub 2]Cu[sub 2]O[sub 8[minus][delta]] is stronger than in Bi[sub 2]Sr[sub 2]([ital L],Ce)[sub 2]Cu[sub 2]O[sub [ital y]]. The transition temperature is actually increased by about 8 K. This result seems to be different from that in Tl-based superconductors. It is also found that the ionic radius of the [ital A] site in the Cu perovskite unit [ital A]CuO[sub 3[minus][delta]] is critical to the formation of the [ital T], [ital T][prime], [ital T][sup *] phases.

Single phase samples (Bi, Pb)2Sr2Ca2Cu3Oy have been prepared under different heat treatments. The midpoint transition temperature (Tc) is determined by both AC susceptibility and resistance measurement. The resistance-temperature coefficient is found changed from positive to negative when the sample is fast cooled. The Hall coefficient measurement shows that Tc increases monotonically with the effective carrier concentration (nH) and that nH increases with temperature linearly. The authors draw the conclusion that the reduction of the carrier concentration is caused not by the reduction of the oxygen content, but by the weak localization of the carriers which is unfavorable to High Tc.

Anisotropic transport properties have been investigated for single crystals Bi 2 Sr 2 CaCu 2 O 8+δ doped with Fe, Co, and Ni. The in plane anisotropy ρ b (T)/ρ a (T) is temperature independent for all crystals. Out-of-plane resistivity ρ c increases in the case of doping with Co and Ni, while monotonously decreasing with increasing Fe concentration. The data of ρ c are well fitted by the activation-type phenomenological formula ρ c (T)=(a/T)exp(Δ/T)+bT+c.

The in-plane resistivity (ρ) and thermopower (S) were measured on Nd1.86Ce0.14CuO4+δ single crystal after different annealing times. Both S and ρ can be described in terms of a two-band model with an electron broad band and a hole-like narrow band. From ρ and S data, we found that the hole component increases with the annealing time before the optimal superconductivity is achieved, while S and ρ reach saturation after further annealing in N2. So the annealing process has the same effect as Ce doping just before the sample is optimally annealed, while after that they are not equal to each other. Furthermore, we also argue that the holes may be responsible for the superconductivity in the electron-doped cuprates.

Nanostructured Bi Sr Ca Cu O oxide ceramics were prepared from amorphous state with the composition of Bi 2 Sr 2 CaCu 2 O 8 . The resistance-temperature characters for nanocrystalline grained samples are discussed in this paper. We found an anomalous peak emerged near T c for one of the nanostructured samples.

The temperature and the magnetic-field dependences of both the Hall resistivity ϱ xy and the longitudinal resistivity ϱ xx in the mixed state of c-axis oriented Hg 0.9 Tl 0.1 Ba 2 Ca 2 Cu 3 O 8+δ superconductivity films with T c > 124K have been measured. It is found that the Hall resistivity ϱ xy shows a sign anomaly and scales with the longitudinal resistivity ϱ xx as ϱ xy( T )= K ϱ xx β (T) with β ≈1.8 and a magnetic-field-independent coefficient K.

We have measured the specific heat of the HgBaCaCuO(1223) samples in low temperature, and found the specific heat jumps of these samples near Tc. It is different from the other Hg-systems. The temperature range of the phase transition is very wide, ΔTc is over 30K. The ac susceptibility shows these samples have one phase transition near Tc. This phenomenon probably is introduced by oxygen inhomogeneity in these samples.

The preparation of nanocrystalline Bi Sr Ca Cu O grain clusters from amorphous state is reported. The crystallization and phase evolution of the nonostructured materials are also discussed. Both the annealing temperature and time control the grain sizes of the samples. The most optimum temperature for crystallizing nanocrystalline Bi Sr Ca Cu O grains is 400°C–750°C.

Nearly single phase Hg(Tl)Ba 2 Ca 2 Cu 3 O 8+δ superconductors have been synthesized. The samples annealed in O 2 had a zero resistace temperature Tc=134K. The onset temperature of Hg(Tl)-1223 phase decomposition was high up to 825°C. The vibration of oxygens shifted to higher frequency (596 cm −1 ). Addition of thallium rised the vibration frequency of oxygens and stabilized the crystal structure of Hg-1223 phase.

Through the RRT program in which six domestic Laboratories were involved, it was concluded that the maximum coefficient of variation on Ic measurement among the Laboratories at 1μV/cm 77K and zero magnetic field for the Ag-sheathed 2223 BSCCO tapes was less than 2.5%, after the measured Ic value was corrected against corresponding measurement temperature.

We have investigated the phase transition of Bi 1.8 Pb 0.2 Sr 2 CaCu 2 O 8 samples with specific heat in low temperature. The phase transition temperatures depend on the oxygen contents. There is a relation between the specific heat anomaly and the oxygen contents in these samples. The specific heat anomaly peak is the largest for the optimum doped sample, the anomaly peaks are decreased for the underdoped samples. There are the phase segregation phenomenon when the oxygen is removed content in these Bi2212 system samples, their transition temperatures are about 60K and 90K. The peak of specific heat anomaly for the overdoped sample (Tc=60K) does not appeared. The resistance measurement shows that the phase transition temperature of these samples are the same as that of the specific heat measurement. The electronic specific heats C e and the Debye temperature θ D are calculated.

The dissipation behavior in the mixed state of YBa2Cu307-y thin film has been studied. It is found that a current-independent resistivity can be described by Arrhenius law and that the activation energy U0 as a function of magnetic field can be described by a power law dependence on H. All of the above results will be included in a vortex glass model.