Superconducting Glass Ceramics Research Articles

Effect of Vanadium Substitution on the Dielectric Properties of Glass Ceramic Bi-2212 Superconductor

Glass ceramic superconductors were prepared by the melt-quenching method. The frequency and temperature dependence of dielectric constant (e′), dielectric loss (e″) and loss tangent (tan δ) of these superconductors were investigated in the frequency range of 10 kHz–10 MHz and temperature range of 80–300 K using the capacitance–voltage (C–V) and conductance-voltage (G/w-V) measurements. Effect of vanadium on bulk properties, dc electrical resistivity (ρ) and ac electrical conductivity (σ ac) of these superconductors were also investigated. The experimental results showed that e′,e″ and σ ac were strongly temperature and frequency dependent. Negative capacitance (NC) phenomenon has been observed and it is believed that the negative capacitance effect is due to polarization effect. The results can be concluded to imply that the interfacial polarization can occur more easily at low frequencies consequently contributing to the deviation of the dielectric properties and ac electrical conductivity of Bi2Sr2Ca1Cu2O δ and Bi1.9V0.1Sr2Ca1Cu2O δ superconductors.

Synthesis and characterization of Er-substituted Bi-2223 H-Tc glass–ceramic superconductors

The Bi2Sr2Ca2Cu3−xErxO10+δ (x = 0.5 and 1.0) H-Tc system was prepared by glass–ceramic technique to investigate the microstructural formation, thermal and transport properties. We have found that Er+3 ions have a solid solubility limit in the Bi-2223 system and this limit was passed at x = 1.0. Below this limit glass samples were prepared and converted to the glass–ceramic form easily, but after the solid solubility limit glass formation was diminished and crystallized samples were formed after melt quenching. The substitution had considerable effect on the electrical properties comparing with the unsubstituted Bi-2223 material. The Tc values of the x = 0.5 and 1.0 sample were found to be 71 ± 0.1K. The thermoelectric power data were analyzed in view of “two band model with linear T-term” and “Xin’s two band model”. Thermoelectric power was obtained to be positive for the both samples, indicating that the hole type conductivity is dominant in the materials prepared. The magnitude of thermal conductivity, κ, was also influenced by the Er concentration. When the Er concentration was increased the magnitude of κ was suppressed. It strongly indicates that the impurities play a significant role in limiting the heat transport due to a strong increase of the electron–phonon-impurity scattering rate.

Effect of Ti doping on the transport properties of thick films of (Bi, Pb)–Sr–Ca–(Cu, Ti)–O-type glass–ceramic superconductors

Abstract Homogeneous thick films (0.34.35 mm thick) of glassy (Bi3Pb1)Sr3Cu3Cu4−n Ti n Ox, precursors with low (n = 0–0.0075) concentrations of Ti have been prepared by a fast-quenching technique and characterized by X-ray diffraction and scanning electron microscopy studies. By annealing these as-quenched glasses above their respective glass transition temperatures T g, mostly the Bi-2212-type superconducting phase is obtained. The effect of Ti doping is to decrease the glass melting temperature as well as the annealing temperature (for making the ceramic phase, hereafter termed glass-ceramic (GC) phase) by about 20°C. The addition of Ti also reduces the formation of the high-T c 2223 phase. However, the superconducting transition temperature Tc decreases linearly with increasing Ti content. The Abrikosov-Gor'kov pairbreaking mechanism is found to be satisfied. All these GC samples (except the n = 0.00 sample) follow Mott's variable-range hopping conduction mechanism above the superconducting transition ...

Effect of Ti doping on the transport properties of thick films of (Bi, Pb)-Sr-Ca-(Cu, Ti)-O-type glass-ceramic superconductors

Effect of Ti doping on the transport properties of thick films of (Bi, Pb)-Sr-Ca-(Cu, Ti)-O-type glass-ceramic superconductors

Depression of superconductivity and the phonon-drag effect in glass-ceramic superconductors obtained by annealing the Fe-doped(Bi,Pb)4Sr3Ca3Cu4−mFemOxglassy precursor

Electrical conductivities and Seebeck coefficients of Fe-doped Bi-2212 type superconductors have been reported in the temperature range 300--10 K. These superconductors are obtained by annealing the Fe-doped amorphous ${\mathrm{Bi}}_{3}{\mathrm{PbSr}}_{3}{\mathrm{Ca}}_{3}{\mathrm{Cu}}_{4\ensuremath{-}m}{\mathrm{Fe}}_{m}{\mathrm{O}}_{x}$ $(m=0.0,$ 0.02, 0.04, 0.05, and 0.06) system around 840 \ifmmode^\circ\else\textdegree\fi{}C for 40 h in air. The superconducting transition temperature ${T}_{c}$ decreases continuously with a gradual increase of Fe content and finally diminishes for $m>~0.06$ supporting the Abrikosov-Gor'kov-type pair-breaking mechanism. Unlike undoped glass ceramics, semiconducting behavior exhibited by all the Fe-doped glass ceramics in their normal states can be explained by Mott's variable range hopping model. The Seebeck coefficients (S) of the glass-ceramic superconductors showed interesting nonlinear variation with temperature. Such nonlinear variation of thermopower is considered to be associated with phonon-drag effect which is, however, not the case in undoped (Fe free) glass-ceramic superconductors. Formation of impurity bonds such as Cu-O-Fe, Fe-O-Fe, etc., is considered to be more important than the magnetic effect for the depression of ${T}_{c}$ and nonlinear thermal variation of Seebeck coefficient (S) in these superconductors.

Erratum: Transport properties of Pb-doped Bi4Sr3Ca3Cu4Ox semiconducting glasses and glass-ceramic superconductors

Erratum: Transport properties of Pb-doped Bi4Sr3Ca3Cu4Ox semiconducting glasses and glass-ceramic superconductors

Oriented crystalline layers on the surface of bismuth superconducting glass ceramics

Oriented crystalline layers on the surface of bismuth superconducting glass ceramics

Transport properties of Pb-doped Bi4Sr3Ca3Cu4Ox semiconducting glasses and glass-ceramic superconductors.

Electrical conductivity and thermoelectric power (TEP) of the as-quenched and annealed (at 500{degree}C for 10 h and 840{degree}C for 24 h) Bi{sub 4{minus}{ital n}}Pb{sub {ital n}}Sr{sub 3}Ca{sub 3}Cu{sub 4}O{sub {ital x}} ({ital x} = 0{endash}1.0) glasses have been measured. The dc conductivity data of the as-quenched and the partially annealed (at 500{degree}C) glasses can be explained by considering the small-polaron hopping conduction mechanism which is found to change from the nonadiabatic to the adiabatic regime with annealing the glasses at 500{degree}C. This change over is due to the presence of microcrystals in the partially annealed glasses as observed from x-ray-diffraction and scanning electron microscopic studies. This adiabatic behavior is also visualized even for some as-quenched glasses having a very small amount of the more conducting microcrystalline phase. All the 840{degree}C annealed glasses are superconductors with {ital T}{sub {ital c}} between 110 and 115 K. The Seebeck coefficient ({ital S}) of the partially annealed glass system is found to be positive and increases linearly with temperature. The {ital S} values of the corresponding glass-ceramic superconductors showing broad peaks around {ital T}{sub {ital c}}. A change over in the values of {ital S} from positive (below {approximately}290 K) to negative (above {approximately}290more » K) indicates the coexistence of both electrons and holes in these superconductors. The TEP data can be fitted with both the two-band model of Forro {ital et} {ital al}. [Solid State Commun. {bold 73}, 501 (1990)] and the Nagaosa-Lee model [Phys. Rev. Lett. {bold 64}, 2450 (1990)]. Therefore, the bosonic contribution in the transport properties of these superconductors, as suggested by the Nagaosa-Lee model, is supported. {copyright} {ital 1996 The American Physical Society.}« less

Crystallization and resistivity studies on Bi 4Sr 3Ca 3Cu yO x glasses

Studies on Bi 4Sr 3Ca 3Cu y O x (433y) glasses (3 ≤ y ≤ 6) and corresponding glass ceramics are reported. No definite correlation is found between the properties of the glasses and the superconducting glass ceramics. The detailed studies, including Differential Scanning Calorimetric, Resistivity and X-ray diffraction, on 4334 glass and glass ceramics show that the activation energy for crystallization is 388 KJ/mol.; the devitrification reaction rate is maximum in the 500–650°C temperature range; Bi 2Sr 2CuO x (Bi-2201) is the first phase which crystallize from the glass and the crystallization is a bulk phenomenon. Metal-insulator transition is observed for RT resistivity 10 −2Ω cm. The Bi 2Sr 2Ca 1Cu 2O x (Bi-2212) phase formation starts above 650°C by a diffusion reaction between Bi-2201 phase, Ca, Cu and O at the sample surface.

STRUCTURAL AND SUPERCONDUCTING PROPERTIES OF Bi4Sr3Ca3CuyOw AND Bi4Sr3Ca3Cu4−xMxOz(M=Fe, Cr AND Mn) GLASS CERAMICS

The synthesis of glass ceramic superconductors of Bi 4 Sr 3 Ca 3 Cu y O w(3≤y≤6) and Bi 4 Sr 3 Ca 3 Cu 4−x M x O z ( M=Fe , Cr , Mn and 0≤x≤0.2) compositions is reported. The 4334 sample is found to be the optimum composition to obtain Bi-2212 superconducting phase. X ray diffraction studies indicate that the solid solubility of 3d metal ions in the 4334 system is limited to x=0.05 in the case of Fe and Cr and x=0.1 in the case of Mn. A systematic decrease in Tc with increasing dopant concentration is observed from resistivity as well as AC susceptibility measurements. Tc depression rates, however, are found to differ for different dopants. XRD studies indicate the decrease in c lattice parameter with increase in dopant content. The systematics of the superconducting transition is discussed in view of Tc depression rates.

Some aspects of glass-ceramic superconductors

In this review article we have discussed, in brief, the general procedure for making glass-ceramic superconductors and some of their physical properties. All these glasses which become superconductors after properly annealing at higher temperatures are, in general, transition metal oxides (TMO) with copper ions. So the usual theoretical models of polaronic hopping conduction mechanisms are valid for explaining the semiconducting behaviour of these oxide glasses. Some of the transport properties of the glass-ceramic (GC) phases, viscosity of the glassy state, wire making feasibility etc have also been discussed in short.

Infrared temperature dependent studies of Bi 2Sr 2CaCu 2O 8 glass ceramic superconductors

We report on the investigation of infrared reflectance spectroscopy on Bi 2Sr 2CaCu 2O 8 glass ceramics superconductor in the temperature range 20 K to 300 K and between the frequency of 100 to 20000cm −1. The frequency dependent conductivity was calculated by Kramer-Kronig transformation of the reflectance spectra. Analysis by Drude and lattice vibration models reveals the Drude plasma frequency and the reflectance edge, closer to those of a single crystal. All the predicted phonon modes are observed in the measured spectra. We did not find any appreciable change in the frequency and oscillator strength of the phonons in the present temperature range.

Processing characteristics and properties of BiSrCaCuO superconducting glass ceramics prepared by melt-quenching

In the framework of an extensive research program for the production of textured and ductile high Tc BiSrCaCuO (BiSCO) wires and tapes, the influence of processing (by melt-quenching) parameters on the crystallization behavior, the quantitative and qualitative evolution of the crystallized phases, the chemical changes in the bulk, and the superconductive properties of various initial compositions of bulk BiSCO glass ceramics, prepared by melt-quenching, have been studied. The elemental composition of the samples changes drastically during heat treatments, affecting mainly Pb, but Sr and Ca also. The identified crystallographic phases, by XRD, were the low Tc superconducting “2201” (Bi2Sr2CuO6) phase, the high Tc superconducting “2212” and “2223” phases, and the Ca2PbO4, Ca2CuO3, CuO, CaO, Bi2Sr3-xCaxOy, and (Ca, Sr)3Cu5O8 “impurities” compounds. A crystallization sequence from the amorphous state is proposed, involving a reaction at 800 °C between “2223”, CaO, Ca2CuO3, and Bi2SrCaxOy to form “2212” + Ca2PbO4 + CuO and a 2(“2212”) → “2223” + “2201” disproportionation reaction that takes place with the intake of oxygen at a higher temperature. Decomposition of Ca2PbO4, which occurs also at high temperature, causes an increase of “2212”, which favors the increase of “2223” through the disproportionation reaction. The glass transition starts around Tg = 400 °C, and the crystallization reactions from the amorphous state proceed in two steps, at Txl = 465 °C and Tx2 = 504 °C. The Bi2Sr3-xCaxOy “2212” and “2223” phases are among the first to crystallize as early as after a 1 h treatment (in air) at 488 °C. A gain in weight is observed by thermogravimetry, caused by intake of the oxygen necessary for the formation of the high Tc superconducting phases. The oxygen intake starts as early as 600 °C. The Tc onset for the “2223” phase is at 122 K, and at 85.5 °C for the “2212” phase. Coefficients of thermal expansion have been measured and shown to differ according to crystallographic direction of expansion. The resistivity is increased on cooling, indicating semiconducting behavior of the 2223 BiSCO ceramic (semiconductor-to-metal transition temperature: 210–220 K).

Phase separated glass and resultant superconducting glass ceramics in BiSrCaCuO (2245) composition

The crystallisation of superconducting phases in a glass of nominal composition Bi 2Sr 2Ca 4Cu 5O y has been found to depend on phase separation within the glass. The most interesting result is the attainment of zero resistance even though the volume fraction of superconducting phase, estimated from Xac measurements, is smaller than 0.1%. These results have been discussed on the basis of exsolution of different phases, partial melting and rearrangement of ions at around grain boundaries. Presumably, a narrow superconducting path is formed along the flow line of the partially melted state.

Studies on Bi-Sr-Ca-Cu-O glasses and superconducting glass ceramics

Bi-Sr-Ca-Cu-O glasses and glass ceramics of various compositions were synthesised. The glass transition temperature varies from 396 to 422°C depending on the glass composition. The bulk glass ceramics of 4334, 4336, 2223 and 4246 compositions show superconductivity when the corresponding glass samples were heat-treated in air at 820°C for 3, 9, 12 and 24 h respectively. X-ray diffraction studies show that the superconducting phase present in all these compositions is Bi2Sr2Ca1Cu2O x . The 4334 glass ceramic is almost a single-phase material with a preferred orientation such that thec axis is normal to the sample surface. The 2223 glass ceramic has a higherT c (onset) than the other three compositions indicating the presence of highT c phase (110K) also. ESR studies on the glass samples indicate the existence of Cu2+. The effect of heat treatment on ESR shows that the intensity of resonance decreases with increase in heat-treatment duration. This effect is more pronounced for the 4334 and 2223 compositions. The advantages of synthesizing superconducting materials by glass route are discussed in view of practical applications.

Critical current density of Bi-Pb-Ca-Sr-Cu-O high T c superconductors via rapidly quenched glass precursors

Two- and three-step heat treatment processes of Bi1.6Pb0.4Ca2Sr2Cu3Ox rapidly quenched precursor glasses were examined to produce dense high Tc superconducting glass ceramics with a high critical current density Jc. The heat treatment at around the glass transition, which was expected to accelerate the nucleation rate, contributed to enhance the Jc values. The maximum Jc value of 1800 A cm−2 was obtained through the three-step heat treatment performed firstly at 350 °C, for 1 h, then at 700 °C for 1 h, and finally at 855 °C for 20 h.

High Tc superconductivity in Bi[sbnd]Ca[sbnd]Sr[sbnd]Cu[sbnd]O-based materials synthesized via glass ceramic methods

Superconducting glass ceramics composed of quasi-oriented platelets 100 to 600μ in size have been obtained by controlled heat treatment of glasses with compositions in the Bi2(CaSr)n+1CunOy (n=1,2,3) family. Samples have Tc=85 K, reaching zero resistance around 70 K. This method of preparation allows for the use of glass processing techniques to form superconducting devices.

Superconducting glass ceramics in BiPbSrCaCuO system

Glass ceramic based superconductors in four different compositions in BiPbSrCaCuO system have been synthesised. The amorphous flakes were initially produced by crucibleless melting between twin rollers. The as prepared amorphous flakes were semiconductors. The different heat-treatment schedules were estimated from thermal analysis measurements. Characterisation of differently heated samples show that the growth of superconducting phase in the amorphous matrix is dependent upon the heat-treatment schedule. The results of X-ray diffraction data is consistent with the results of resistivity, AC susceptibility and optical microstructure.

Magnetic measurements of superconducting glass-ceramic fine rods in Bi1Ca1Sr1Cu2Al0.5Ox prepared under a temperature gradient

It is shown that the crystallization of the glass precursor under a temperature gradient is very effective for preparing the superconducting glass ceramics in the Bi-Ca-Sr-Cu-O system. The magnetization measurements show that the specimen prepared under a temperature gradient has a magnetization hysteresis several times larger at 4.2 K than that prepared under no temperature gradient; the coupling between superconducting grains of the former is stronger than that of the latter.

Superconducting glass ceramics with T c=100 K based on the Bi-Pb-Sr-Ca-Cu-O system

Superconducting glass ceramics of Bi0.8Pb0.2SrCaCu1.5Oy (sample A) and BiPb0.2SrCaCu1.5Oy (sample B) have been prepared by using the melt quenching method. It was found that the volume fraction of the high Tc phases in sample A annealed at 830 or 840 °C for 250 h was much higher than that in sample B. The annealed (840 °C, 250 h) sample A exhibited superconductivity with a Tc (zero) of 100 K and a critical current density (77 K, zero magnetic field) of 120 A/cm2.