Bulk ceramic samples with chemical composition (${\rm Y}_{1-x}$ ,${\rm Nd}_{x}$)Ba2 Cu3O7-δ, where x = 0, 0.1, 0.2, 0.5, and 1 were sintered by a proposed acetate method. The samples were then submitted to structural characterization by X-ray diffraction with crystal structure refining using the Rietveld method. AC electrical resistivity measurements from ambient temperatures down to 4.2 K were performed, as well as magnetic measurements of magnetic moment as function of temperature and magnetic hysteresis loop. Results have shown superconductivity with critical temperatures of about 91 and 60 K for pure YBa2Cu3O7-δ (x = 0) and pure NdBa2Cu3O7-δ (x = 1) samples, respectively. Scanning electron microscopy images were also analyzed, revealing a regular parallel-piped grain shape. The proposed method showed as an advantage to reduce the grinding time without any considerable degradation on structural or superconducting properties of pure YBa2Cu3O 7-δ (x = 0) or pure NdBa2Cu3O7-δ ( x = 1), as related to samples prepared by a conventional solid state route.

We present an extensive study of the ferromagnetic heavy fermion compound U$_4$Ru$_7$Ge$_6$. Measurements of electrical resistivity, specific heat and magnetic properties show that U$_4$Ru$_7$Ge$_6$ orders ferromagnetically at ambient pressure with a Curie temperature $T_{C} = 6.8 \pm 0.3$ K. The low temperature magnetic behavior of this soft ferromagnet is dominated by the excitation of gapless spin-wave modes. Our results on the transport properties of U$_4$Ru$_7$Ge$_6$ under pressures up to $2.49$ GPa suggest that U$_4$Ru$_7$Ge$_6$ has a putative ferromagnetic quantum critical point (QCP) at $P_c \approx 1.7 \pm 0.02$ GPa. In the ordered phase, ferromagnetic magnons scatter the conduction electrons and give rise to a well defined power law temperature dependence in the resistivity. The coefficient of this term is related to the spin-wave stiffness and measurements of the very low temperature resistivity allow to accompany the behavior of this quantity as the the ferromagnetic QCP is approached. We find that the spin-wave stiffness decreases with increasing pressure implying that the transition to the non-magnetic Fermi liquid state is driven by the softening of the magnons. The observed quantum critical behavior of the magnetic stiffness is consistent with the influence of disorder in our system. At quantum criticality ($P = P_c \approx 1.7 \pm 0.02$ GPa), the resistivity shows the behavior expected for an itinerant metallic system near a ferromagnetic QCP.

Bulk ceramic samples with chemical composition (Y1-x,Nd-x)Ba2Cu3O7-delta, where x = 0, 0.1, 0.2, 0.5, and 1 were sintered by a proposed acetate method. The samples were then submitted to structural characterization by X-ray diffraction with crystal structure refining using the Rietveld method. AC electrical resistivity measurements from ambient temperatures down to 4.2 K were performed, as well as magnetic measurements of magnetic moment as function of temperature and magnetic hysteresis loop. Results have shown superconductivity with critical temperatures of about 91 and 60 K for pure YBa2Cu3O7-delta (x = 0) and pure NdBa2Cu3O7-delta (x= 1) samples, respectively. Scanning electron microscopy images were also analyzed, revealing a regular parallel-piped grain shape. The proposed method showed as an advantage to reduce the grinding time without any considerable degradation on structural or superconducting properties of pure YBa2Cu3O7-delta (x= 0) or pure NdBa2Cu3O7-delta (x= 1), as related to samples prepared by a conventional solid state route.

Bulk ceramic samples with chemical composition (Y 1-x Nd x )Ba 2 Cu 3 O 7-δ , where x = 0, 0.1, 0.2, 0.5, and 1 were sintered by a proposed acetate method. The samples were then submitted to structural characterization by X-ray diffraction with crystal structure refining using the Rietveld method. AC electrical resistivity measurements from ambient temperatures down to 4.2 K were performed, as well as magnetic measurements of magnetic moment as function of temperature and magnetic hysteresis loop. Results have shown superconductivity with critical temperatures of about 91 and 60 K for pure YBa 2 Cu 3 O 7-δ (x = 0) and pure NdBa 2 Cu 3 O 7-δ (x = 1) samples, respectively. Scanning electron microscopy images were also analyzed, revealing a regular parallel-piped grain shape. The proposed method showed as an advantage to reduce the grinding time without any considerable degradation on structural or superconducting properties of pure YBa 2 Cu 3 O 7-δ (x = 0) or pure NdBa 2 Cu 3 O 7-δ ( x = 1), as related to samples prepared by a conventional solid state route.

This paper presents, in development in Brazil, a research for an ac three-phase cold dielectric (CD) high-temperature superconducting (HTS) power cable. That cable was rated to operate mainly at 69 kV/300 A. The first phase of research was part of a National Strategic Project for power transfer in Brazil. The research over the last two years included an improvement in design in order to enable operation also at higher voltages. The cable design changed and now each phase is inside its own cryostat. The electric isolation also changed. It was selected a laminated dielectric material not yet used (to our knowledge) in any other HTS power cable project. The main outcomes and results presented here are i) the improved cable design, ii) the characterizations of the new isolating material, iii) the facilities for cable construction and high-current tests, iv) one demonstrative model for one phase of the cable, and v) the validation of the new cable geometry by numerical simulation of electromagnetic and thermal behaviors of one of its phases at the rated voltage and current. As a conclusion, the results allowed to improve and disseminate the feasibility of the CD HTS cable technology in Brazil. Some details are not shown because they are patent pending.

Bulk ceramic samples with chemical composition (${\rm Y}_{1-x}$ ,${\rm Nd}_{x}$)Ba2 Cu3O7-δ, where x = 0, 0.1, 0.2, 0.5, and 1 were sintered by a proposed acetate method. The samples were then submitted to structural characterization by X-ray diffraction with crystal structure refining using the Rietveld method. AC electrical resistivity measurements from ambient temperatures down to 4.2 K were performed, as well as magnetic measurements of magnetic moment as function of temperature and magnetic hysteresis loop. Results have shown superconductivity with critical temperatures of about 91 and 60 K for pure YBa2Cu3O7-δ (x = 0) and pure NdBa2Cu3O7-δ (x = 1) samples, respectively. Scanning electron microscopy images were also analyzed, revealing a regular parallel-piped grain shape. The proposed method showed as an advantage to reduce the grinding time without any considerable degradation on structural or superconducting properties of pure YBa2Cu3O 7-δ (x = 0) or pure NdBa2Cu3O7-δ ( x = 1), as related to samples prepared by a conventional solid state route.