The MRS Symposium Proceeding series is an internationally recognised reference suitable for researchers and practitioners.

The discovery of high temperature superconductors (HTS) in 1986 by two IBM scientists led to an unprecedented explosion of research and development efforts world-wide because of the significant potential for practical applications offered by these materials. However, the early euphoria created by the exciting prospects was dampened by the daunting task of fabricating these materials into useful forms with acceptable superconducting properties. Progress towards this goal has been hindered by many intrinsic materials problems, such as weak-links, flux-creep, and poor mechanical properties.

The above problems led to the development of the Second-Generation of HTS wires. Three methods were invented to produce flexible metallic substrates, which were also crystallographically biaxially textured, and resembled a long, mosaic single crystal. The first method invented is the Ion-Beam-Assisted-Deposition (IBAD). The second method developed was the Inclined-Substrate-Deposition (ISD). The third method invented is called the Rolling-assisted-biaxially-textured-substrates (RABiTS).

The book is divided into four sections. The first section discusses the three methods to fabricate biaxially textured substrates, upon which, epitaxial YBCO or other HTS materials can be deposited to realize a single-crystal-like HTS wire. The second section includes chapters on various methods of HTS deposition such as pulsed laser ablation (PLD), thermal co-evaporation, sputtering, pulsed electron beam deposition, ex-situ BaF2 by co-evaporation flowed by annealing, chemical solution based ex-situ processes, jet vapor deposition, metal organic chemical vapor deposition (MOCVD), and liquid phase epitaxy (LPE).The third section includes detailed chapters on other HTS materials such as the various Tl-based and Hg-based conductors.

These Second-Generation HTS conductors, also referred to as "Coated conductors" represent one of the most exciting developments in HTS technology. HTS wires based on this technology have the potential to carry 100-1000 times the current without resistance losses of comparable copper wire. HTS power equipment based on these HTS conductors has a potential to be half the size of conventional alternatives with the same or higher power rating and less than one half the energy losses. Upgrading of the world-wide electric power transmission and distribution with HTS based devices can significantly help in meeting the growing demand for electricity world-wide. There is little question that superconducting technology based on the Next-Generation HTS Superconducting Wires will make a substantial impact on the way we generate, transmit, distribute and use electric power. Of course the question is - how soon?

Thediscoveryofhightemperaturesuperconductors(HTS)in 1986bytwoIBM scientists led to an unprecedented explosion of research and development efforts world-wide because of the signi?cant potential for practical applications offered by these materials. However, the early euphoria created by the exciting prospects was dampenedby the dauntingtask of fabricating these materials into useful forms with acceptablesuperconductingproperties. Progresstowardsthisgoalhasbeen hindered by many intrinsic materials problems, such as weak-links, ?ux-creep, and poor - chanicalproperties. TheearlieststudiesofcriticalcurrentdensityJ inHTSmaterialsrevealedthatfor c apolycrystallinematerialcontainingadistributionofgrainboundariesismuchlower than that for a single crystal. High angle grain boundariesact as Josephson coupled weak-links leading to a signi?cant ?eld-dependent suppression of the supercurrent acrosstheboundary. Forcleanstoichiometricboundaries, thegrainboundarycritical currentdensity dependsprimarilyonthe grainboundarymisorientation. The dep- denceof J (gb)onmisorientationanglehasbeendeterminedYBa O Cu (YBCO) c 2 3 7 in boundary types which can be formed in epitaxial ?lms on bicrystal substrates. Theseinclude 001]tilt, 100]tilt, and 100]twistboundaries. Ineachcasehighangle boundarieswerefoundtobeweak-linked. Theseexperimentshavealsobeenextended to arti?cially fabricated 001] tilt bicrystals in Tl Ba CaCu O, Tl Ba Ca Cu O, 2 2 2 8 2 2 2 3 x TlBa Ca Cu O (Tl-1223) and Nd Ce CuO . In each case it was found that, 2 2 3 x 1. 85 0. 15 4 as in YBCO, J depends strongly on grain boundary misorientation angle. Data on c currenttransmissionacrossarti?ciallyfabricatedgrainboundariesinBi-2212also- dicate that most large angle 001] tilt and 001] twist boundaries are weak links. It is likely that the variation in J with grain boundary misorientation is similar in all c high-T superconductors. Hence, thelow J observedinrandomlyorientedpolycr- c c tallineHTScanbeunderstoodonthebasisthatthepopulationoflowangleboundaries issmallandthatfrequenthighangleboundariesimpedelong-rangecurrent?ow. - ingconventionalprocessingtechniques, threeHTSmaterialsweresuccessfullyfab- catedinpolycrystallineformwithmodestJ 's. ThesearetheBi-2223powder-in-tube c conductors, theTl-1223spray-pyrolyzed?lmsandtheBi-2212melt-processedthick ?lms. Thesethreetypesofconductorscomprisedthe First-GenerationHTScond- torsorwires.

Self-etching primers are the latest addition to the armamentarium of an orthodontist. Their main advantage is that they reduce the number of steps required in the bonding of orthodontic brackets. However, their low ph was a cause of concern. This book describes a study undertaken to see the effects of ph of self-etchant on shear bond strength of orthodontic brackets. These shear bond strengths were also compared to those obtained with a conventional 3-step bonding system. It was found that self-etching primers not only reduce the chair time in an orthodontist's clinic but also reduce the amount of enamel lost during etching. The bond strength achieved was less than that of the conventional bonding system but was acceptable for orthodontic purposes. Thus self-etching primers are an important and useful invention for simplifying the most critical step in orthodontic clinic- bonding.

The MRS Symposium Proceeding series is an internationally recognised reference suitable for researchers and practitioners.