Role of Electronic Relaxation Rates in the Casimir Force between High-Tc Superconductors

We revisit the problem of the Casimir force between high-Tc superconductors below and above the critical temperature for the superconducting transition. Ceramic superconductors exhibit a different temperature dependence of the reflectivity when switching from the normal to the superconducting state. We leverage this unique characteristic with respect to ordinary metals to claim that these kind of materials can prove useful as an alternative system where the long-standing discussion on the role of electronic relaxation can be addressed. Furthermore, we show that the two main damping mechanisms associated with free and mid-infrared electrons dominate at very distinct scales, meaning that they can be considered separately when the Casimir force is measured as a function of slab distance. This facilitates the experimental identification of the role of the two electronic relaxation contributions to the force.

Superconducting Properties of YBaCuO Bulk Superconductors

The use of a high-temperature superconductor to manufacture products for commercialization requires a superconductor with a flexible function designed to meet the characteristics of each product. Appropriate mechanical properties need to be maintained to overcome the Lorenz force generated under high magnetic fields. Several studies focused on the improvement of superconductivity and the development of processing technology. However, high temperature superconductivity wires are not intended for large-scale applications at liquid nitrogen temperature (77 K). Recently, ceramic superconductors have been fabricated into bulk and thin films or wire rods for electric power applications; however, ceramics are hard to deform due to increased hardness, which is one of the biggest limitations of a superconductor, and a major obstacle to industrial applications. To overcome these limitations, a synthetic method for superconductivity to reduce the hardness of ceramic superconductor and prevent its degradation was proposed for applications such as superconductivity power cables and wires in energy and electric machines using superconductors.

Some eects of the doping with alpha - Al_2O_3 nanoparticles in the transport properties of Bi_1.65 Pb_0.35 Sr_2Ca_2 Cu_3O_y ceramic superconductors

We present a preliminary study on the eects of alpha - Al_2O_3 nanoparticles (NPs) in the transport properties of Bi_1.65 Pb_0.35 Sr_2Ca_2 Cu_3O_y ((Bi,Pb)-2223) ceramic samples. The (Bi,Pb)-2223 samples were synthesized by the solid state reaction method and alpha - Al_2O_3 NPs, with concentrations ranging from 0.1 to 0.8 wt. percent (% wt.), were added before the last heat treatment. All samples were characterized by means of X-rays diraction patterns, and temperature and magnetic eld dependence of the electrical resistivity, rho(T;Ba). From the experimental (T;Ba) data we extracted the critical temperature dependence of the % wt. of alpha - Al_2O_3 NPs, and by using the Arrheniusplot the eective pinning energy has been also determined. The results indicate that mostly of the transport properties are optimized for the sample B03.

Nanostructured A2(RE,B)O6 (A = Ba, Sr; RE = Rare-Earth; B = Sb, Zr) Perovskite Ceramics and their Potential Applications in Microwave and Superconducting Electronics

A group of perovskites with general formula A2(RE,B)O6(A=Ba, Sr; RE=Rare-Earth; B=Sb, Zr) were synthesized as nanocrystals owing to the enhanced specific surface area that nanomaterials posses. These perovskites are characterized by varied crystal structure depends on the relative sizes of the cations occupying the A and B sites of the perovskite lattice. The new materials were either insulators or semiconductors. They possess moderate dielectric constant (~30) and relatively low dielectric loss (10-4); and therefore, they could be used as substrates in microwave circuits. Some of them falls to the semiconducting range with band gap ~3.3 eV; and therefore, could be used as transparent wide band gap semiconductors. Furthermore, the new perovskites were found to be chemically stable with two mostly considered high temperature ceramic superconductors for practical applications, viz. YBa2Cu3O7-δ(YBCO) and (Bi,Pb)2Sr2Ca2Cu3Ox(BSCCO).