Jahresbericht 2005 - IPHT Jena

MAGNETIK & QUANTENELEKTRONIK / MAGNETICS & QUANTUM ELECTRONICS
Fig. 1.12: Correlation between the m.a.c. values
and the intensity ratio R = I(20 keV)/I(7 keV).
difference leads to effects of differential absorption,
where the absorption is stronger for
decreasing line energy. For the net peak height
ratio β 1/α we obtained results which are of the
same order of magnitude as those given by
White and Johnson (W&J) in their popular tables.
However for l/α and β 3,4/β 1 our results show an
atomic number dependence which is completely
different from those given by W&J.
1.2.9 Preparation, characterization and
application of melt-textured YBCO
(Wolfgang Gawalek, Tobias Habisreuther)
Our work is based on a stable preparation technology
to prepare high quality material combined
with an adapted characterization technology.
Investigation on the whole chain from precursor
preparation to the system integration of function
elements is performed in order to optimize melttextured
YBCO for applications.
Several projects and co-operations with partners
in research and industry of Germany, Europe and
world wide support our work.
Silvia Kracunovska successfully defended her
PhD thesis on the relation between preparation
and microstructure.
General material development
Any application requires material with good and
reproducible quality. This is provided by our batch
process. We are able to prepare several sizes of
monoliths according to the requirements of the
application (D. Litzkendorf).
To enlarge the monoliths size and to improve the
magnetic properties we concentrated on the
multi-seeding technique where several seeds
were placed on the monoliths.
Both and growth fronts were investigated
used polarised light microscopy (J. Bierlich,
PhD work). In both orientations a transport
current across the grain boundaries is observed
in the trapped field profile. The seeds have to be
oriented with an accuracy of about 3° in a distance
less than 5 mm. Fig. 1.13 shows a mono-
Fig. 1.13: Melt-textured YBCO monolith prepared
using 7 seeds.
lith with a size of 78 * 38 * 18 mm 3 where 7 seeds
in orientation were applied. The trapped
field profile (Fig. 1.14) represents a transport current
across all grain boundaries.
Fig. 1.14: Trapped flux distribution of the multiseeded
monolith. The flux distribution shows a
transport current across all grain boundaries.
Within the EFFORT consortium we use the possibility
to exchange and discuss the latest developments
and results with all European specialists.
Applications
In co-operation with MAI Moscow motor tests at
temperatures at 20 K were performed. Small
scale reluctance motors were tested at the MAI
Moscow. The power output of an YBCO-motor
increased from 500 W at 77 K to 1500 W at 20 K
and 3000 rpm.
In 2005 we and our project-partners Oswald
Elektromotoren GmbH, MAI Moscow, and Arburg
GmbH developed first designs for the BMBF-project
“Hochdynamischer HTSL Motor”.
In the frame of the POWER SCENET W.
Gawalek leads the working group “Rotating
machines”. A meeting with 20 participants from
10 countries was organized in Jena from April
11–12, 2005 in Jena.
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