+----------------+-----------------+----------------------------------+---+
| > Phase        |                 | *Phase diagrams serve as "road   |   |
| >              |                 | maps" for successful processing  |   |
|  Relationships |                 | of high T~c~ superconductor      |   |
| > in           |                 | materials. Of current interest   |   |
| >              |                 | are the Ba~2~RCu~3~O~6+x~ (R=Sm, |   |
| > High         |                 | Gd and Er) superconductors. The  |   |
| > Temperature  |                 | critical single-phase regions of |   |
| >              |                 | B                                |   |
| > S            |                 | a~2-x~(Nd~1+x-y~R~y~)Cu~3~O~6+z~ |   |
| uperconductors |                 | for R=Gd,Y and Yb were           |   |
|                |                 | determined such that both        |   |
|                |                 | flux-pinning and melting         |   |
|                |                 | properties can be tailored and   |   |
|                |                 | optimized. The construction of   |   |
|                |                 | subsolidus phase diagrams of     |   |
|                |                 | these systems and the role of    |   |
|                |                 | phase equilibria and kinetics in |   |
|                |                 | the formation of the             |   |
|                |                 | Ba~2~YCu~3~O~6+x~ phase using    |   |
|                |                 | barium fluoride amorphous        |   |
|                |                 | precursor films are deemed       |   |
|                |                 | important for rapid advancement  |   |
|                |                 | of second generation coated      |   |
|                |                 | conductor technology.*           |   |
+----------------+-----------------+----------------------------------+---+
| > Winnie       |                 |                                  |   |
| > Wong-Ng and  |                 |                                  |   |
| > Lawrence     |                 |                                  |   |
| > Cook         |                 |                                  |   |
+----------------+-----------------+----------------------------------+---+
|                |                 |                                  |   |
+----------------+-----------------+----------------------------------+---+
| NIST phase     |                 | have also initiated a more       |   |
| equilibrium    |                 | detailed study of the melt       |   |
| research has   |                 | equilibria in the                |   |
| continued to   |                 | BaF~2~-BaO-Y~2~O~3~-CuO~x~       |   |
| provide        |                 | system. The role of Ba(OH)~2~ in |   |
| critical       |                 | this system as related to        |   |
| information    |                 | low-temperature melting was      |   |
| pertinent to   |                 | identified as warranting further |   |
| the            |                 | investigation. All this          |   |
| development of |                 | information is important for     |   |
| practical      |                 | both the "BaF~2~" process and    |   |
| su             |                 | liquid phase epitaxy process.    |   |
| perconductors. |                 |                                  |   |
| DOE has        |                 | In order to control film         |   |
| supported high |                 | properties, it is important to   |   |
| T~c~ research  |                 | understand the details of the    |   |
| through a      |                 | Y-213 phase evolution from       |   |
| program of     |                 | amorphous "BaF~2~" films. In     |   |
| intensive R&D  |                 | order to collect data at a       |   |
| focused on     |                 | faster rate over a broader       |   |
| wire and cable |                 | range, this year we have         |   |
| for            |                 | successfully set up a position   |   |
| high-impact    |                 | sensitive detector on the        |   |
| commercial     |                 | high-temperature x-ray           |   |
| applications,  |                 | diffractometer. Three sets of    |   |
| of which the   |                 | films with different thickness   |   |
| NIST phase     |                 | (provided by R. Feenstra of the  |   |
| equilibria     |                 | Oak Ridge National Laboratory)   |   |
| project is an  |                 | have been studied. We found that |   |
| integral part. |                 | the growth of the Y-213 phase is |   |
| This effort    |                 | controlled by the reaction at    |   |
| includes three |                 | the interface of the             |   |
| principal      |                 | Y-213/precursor, not by          |   |
| groups of      |                 | diffusion. Sufficient water      |   |
| s              |                 | vapor pressure is critical for   |   |
| uperconductors |                 | Y-213 formation. The detailed    |   |
| as follows:    |                 | phase evolution sequence,        |   |
| (1) 1^st^      |                 | kinetics of phase formation, and |   |
| generation     |                 | the texture of these films as a  |   |
| Bi             |                 | function of processing           |   |
| -Pb-Sr-Ca-Cu-O |                 | parameters, will continue to be  |   |
| (BSCCO)-based  |                 | pursued.                         |   |
| wire/tape      |                 |                                  |   |
| produced by    |                 | A smaller effort was spent on    |   |
| the            |                 | the study of the melting         |   |
| Ag-            |                 | equlibria of the Pb-doped and    |   |
| powder-in-tube |                 | Pb-free Bi-2223 superconductors. |   |
| (PIT)          |                 | In collaboration with FSU, the   |   |
| technique; (2) |                 | Pb-free 2223 phase was found to  |   |
| 2^nd^          |                 | be in equilibrium with eight     |   |
| generation     |                 | phases in the Bi-Sr-Ca-Cu-O      |   |
| Ba~2~R         |                 | system. Investigation continues  |   |
| Cu~3~O~7~-type |                 | to obtain a complete set of      |   |
| (Y-213 and     |                 | subsolidus 4-phase volumes,      |   |
| R-213,         |                 | which is necessary for the       |   |
| R=lanthanide)  |                 | determination of the primary     |   |
| coa            |                 | phase field. We have measured    |   |
| ted-conductors |                 | enthalphy of formation of        |   |
| produced by    |                 | MgB~2~, at 298K by solution      |   |
| rolling        |                 | calorimetry. The vapor pressure  |   |
| assisted       |                 | of MgB~2~ up to 1100 ºC was also |   |
| biaxially      |                 | successfully measured using a    |   |
| textured       |                 | thermogravimetric effusion       |   |
| substrate/ion  |                 | method.                          |   |
| beam assisted  |                 |                                  |   |
| deposition     |                 | As data accumulate, we           |   |
| (RABiTS/IBAD); |                 | anticipate increased use of      |   |
| (3) the        |                 | thermodynamic methods for data   |   |
| recently       |                 | smoothing and extrapolation,     |   |
| discovered     |                 | with the ultimate goal of        |   |
| MgB~2~         |                 | producing a comprehensive phase  |   |
| material.      |                 | equilibria model for each of the |   |
|                |                 | three major high T~c~ systems.   |   |
| By mixing the  |                 | By providing the phase equlibria |   |
| smaller        |                 | data as the basis for optimal    |   |
| lanthanides    |                 | processing, high T~c~ technology |   |
| (Gd, Y, Yb)    |                 | will be advanced through         |   |
| with the       |                 | reductions in cost and           |   |
| larger size Nd |                 | improvements in performance.     |   |
| in the         |                 |                                  |   |
| Ba~2-          |                 |                                  |   |
| x~(Nd~1+x-y~R~ |                 |                                  |   |
| y~)Cu~3~O~6+z~ |                 |                                  |   |
| (Nd-213)       |                 |                                  |   |
| s              |                 |                                  |   |
| uperconductor, |                 |                                  |   |
| both           |                 |                                  |   |
| flux-pinning   |                 |                                  |   |
| and melting    |                 |                                  |   |
| properties can |                 |                                  |   |
| be tailored    |                 |                                  |   |
| and optimized. |                 |                                  |   |
| A trend of the |                 |                                  |   |
| size of the    |                 |                                  |   |
| single phase   |                 |                                  |   |
| solid solution |                 |                                  |   |
| prepared in    |                 |                                  |   |
| air was        |                 |                                  |   |
| observed. Due  |                 |                                  |   |
| to the closer  |                 |                                  |   |
| match in size  |                 |                                  |   |
| of Nd^3+^ with |                 |                                  |   |
| Gd^3+^ than    |                 |                                  |   |
| Nd^3+^ with    |                 |                                  |   |
| Y^3+^, and     |                 |                                  |   |
| Nd^3+^ with    |                 |                                  |   |
| Yb^3+^, the    |                 |                                  |   |
| solid solution |                 |                                  |   |
| region is      |                 |                                  |   |
| largest for    |                 |                                  |   |
| the            |                 |                                  |   |
| Gd-substituted |                 |                                  |   |
| system and     |                 |                                  |   |
| smallest for   |                 |                                  |   |
| the            |                 |                                  |   |
| Yb-substituted |                 |                                  |   |
| system. We     |                 |                                  |   |
| have           |                 |                                  |   |
| successfully   |                 |                                  |   |
| characterized  |                 |                                  |   |
| selected solid |                 |                                  |   |
| solution       |                 |                                  |   |
| members by     |                 |                                  |   |
| x-ray,         |                 |                                  |   |
| neutron, and   |                 |                                  |   |
| electron       |                 |                                  |   |
| diffraction    |                 |                                  |   |
| techniques,    |                 |                                  |   |
| and by         |                 |                                  |   |
| differential   |                 |                                  |   |
| thermal        |                 |                                  |   |
| analysis       |                 |                                  |   |
| (DTA). There   |                 |                                  |   |
| is a           |                 |                                  |   |
| considerable   |                 |                                  |   |
| improvement of |                 |                                  |   |
| J~c~(H) for    |                 |                                  |   |
| samples with   |                 |                                  |   |
| partial        |                 |                                  |   |
| Y-substitution |                 |                                  |   |
| at higher      |                 |                                  |   |
| field at 77K,  |                 |                                  |   |
| as compared    |                 |                                  |   |
| with that of   |                 |                                  |   |
| Ba~2           |                 |                                  |   |
| ~NdCu~3~O~6+z~ |                 |                                  |   |
| and            |                 |                                  |   |
| Ba~2           |                 |                                  |   |
| ~YCu~3~O~6+z~. |                 |                                  |   |
| This           |                 |                                  |   |
| improvement is |                 |                                  |   |
| likely due to  |                 |                                  |   |
| the increased  |                 |                                  |   |
| flux pinning   |                 |                                  |   |
| as a result of |                 |                                  |   |
| doping of      |                 |                                  |   |
| Nd^3+^ in the  |                 |                                  |   |
| Ba^2+^ site.   |                 |                                  |   |
|                |                 |                                  |   |
| The "BaF~2~    |                 |                                  |   |
| *ex-situ*"     |                 |                                  |   |
| process and    |                 |                                  |   |
| the            |                 |                                  |   |
| liquid         |                 |                                  |   |
| -phase-epitaxy |                 |                                  |   |
| process are    |                 |                                  |   |
| promising      |                 |                                  |   |
| methods for    |                 |                                  |   |
| producing      |                 |                                  |   |
| long-length    |                 |                                  |   |
| high quality   |                 |                                  |   |
| Y-213          |                 |                                  |   |
| s              |                 |                                  |   |
| uperconductor. |                 |                                  |   |
| Therefore      |                 |                                  |   |
| investigation  |                 |                                  |   |
| of the phase   |                 |                                  |   |
| relationships  |                 |                                  |   |
| in the system  |                 |                                  |   |
| BaF~           |                 |                                  |   |
| 2~-BaO-Y~2~O~3 |                 |                                  |   |
| ~-CuO~x~-H~2~O |                 |                                  |   |
| is another     |                 |                                  |   |
| area of        |                 |                                  |   |
| concentration. |                 |                                  |   |
| Using          |                 |                                  |   |
| specially      |                 |                                  |   |
| constructed    |                 |                                  |   |
| controlled     |                 |                                  |   |
| atmosphere     |                 |                                  |   |
| i              |                 |                                  |   |
| nstrumentation |                 |                                  |   |
| and a          |                 |                                  |   |
| strategic      |                 |                                  |   |
| approach, we   |                 |                                  |   |
| succeeded in   |                 |                                  |   |
| determining    |                 |                                  |   |
| the presence   |                 |                                  |   |
| of low         |                 |                                  |   |
| temperature    |                 |                                  |   |
| liquids in     |                 |                                  |   |
| this           |                 |                                  |   |
| air-sensitive  |                 |                                  |   |
| multicomponent |                 |                                  |   |
| reciprocal     |                 |                                  |   |
| Ba-Y-Cu//O,F   |                 |                                  |   |
| system, which  |                 |                                  |   |
| can be modeled |                 |                                  |   |
| in             |                 |                                  |   |
| compositional  |                 |                                  |   |
| space as a     |                 |                                  |   |
| trigonal       |                 |                                  |   |
| prism. This    |                 |                                  |   |
| prism can be   |                 |                                  |   |
| viewed as      |                 |                                  |   |
| consisting of  |                 |                                  |   |
| three          |                 |                                  |   |
| tetrahedra     |                 |                                  |   |
| (BaO-Y~        |                 |                                  |   |
| 2~O~3~-CuO~x~- |                 |                                  |   |
| BaF~2~,        |                 |                                  |   |
| BaF~2~-YF~3~-  |                 |                                  |   |
| CuF~2~-CuO~x~, |                 |                                  |   |
| and            |                 |                                  |   |
| Ba             |                 |                                  |   |
| F~2~-Y~2~O~3~- |                 |                                  |   |
| CuO~x~-YF~3~). |                 |                                  |   |
| We             |                 |                                  |   |
+----------------+-----------------+----------------------------------+---+
| >              | > NIST          |                                  |   |
|  Contributors\ | > participants: |                                  |   |
| > and\         | > I. Levin, M.  |                                  |   |
| >              | > Vaudin, J.P.  |                                  |   |
|  Collaborators | > Cline         |                                  |   |
|                | > (Ceramics);   |                                  |   |
|                | > NIST cross OU |                                  |   |
|                | >               |                                  |   |
|                |  collaborators: |                                  |   |
|                | > Q. Huang, B.  |                                  |   |
|                | > Toby          |                                  |   |
|                | > (Reactor), L. |                                  |   |
|                | >               |                                  |   |
|                |  Swartzendruber |                                  |   |
|                | > (Metallurgy), |                                  |   |
|                | > A. Kearsley   |                                  |   |
|                | > (Mathematical |                                  |   |
|                | > and           |                                  |   |
|                | > Computational |                                  |   |
|                | > Sciences), R. |                                  |   |
|                | > Klein         |                                  |   |
|                | > (Chemistry);  |                                  |   |
|                | > Industrial,   |                                  |   |
|                | > government    |                                  |   |
|                | > and academic  |                                  |   |
|                | >               |                                  |   |
|                |  collaborators: |                                  |   |
|                | > T. Holesinger |                                  |   |
|                | > (LANL), R.    |                                  |   |
|                | > Feenstra      |                                  |   |
|                | > (ORNL), M.    |                                  |   |
|                | > Rupich        |                                  |   |
|                | > (AMSC), J.    |                                  |   |
|                | > Storer (3M),  |                                  |   |
|                | > J. Kaduk      |                                  |   |
|                | > (BP-Amoco),   |                                  |   |
|                | > R. Meng (U.   |                                  |   |
|                | > Houston), M.  |                                  |   |
|                | > Suenaga       |                                  |   |
|                | > (BNL), and    |                                  |   |
|                | > PVPSS Sastry  |                                  |   |
|                | > (FSU).        |                                  |   |
+----------------+-----------------+----------------------------------+---+