This is an update on the
continuing work of Joe Eck in establishing high threshold superconductors. They have long since demonstrated room
temperature effects. Now we have jumped
anther 6C to 48C which pretty well establishes the class of materials and the
procedures used. Practical applications
are not addressed here but need to be since we do now have seriously attractive
operating temperatures to work with.
This has been unfolding over
the past several years and remains generally ignored as far as general press
coverage is concerned even though it is obviously a great story about half a
century of scientific perseverance by many individual researchers.
Then again, I have published
the generalized cyclic function which generates higher order Pythagorean
metrics and no one wants to do their homework.
They must like been stuck on second order solutions.
Pushing PWD to Make a
48C Superconductor
29 October 2013
Superconductors.ORG
Superconductors.ORG
herein reports the discovery of two new room-temperature superconductors with
record high transitions near 48 Celsius (118F, 321K) and 44 Celsius (111F,
317K). The chemical formulas of these materials are Tl6Ba4SiCu9O18+ and Tl5Ba4SiCu8O16+ respectively. These are the ninth and tenth
superconductors found to have transition temperatures above room temperature1.
Since dozens of new superconductors have already been found through the application
of planar weight disparity (PWD) along the "C" axis, an effort was
made to further increase the unit cell size and planar weight ratios (PWR) of
materials already producing extraordinarily high transition temperatures. In
the first compound, barium (Ba) was substituted into the tin (Sn) atomic sites
of the 42 C superconductor discovered in
September. This produced a 44 Celsius critical transition temperature (shown
below right). Then, in the second compound, the lattice was expanded to near 33
Angstroms by inserting another Tl and another CuO2 layer. This
altered the structure from a D212 to an F212 (shown below left). That material
produced a record Meissner transition near 48 Celsius.
The plots at page top show
diamagnetic transitions for both warming and cooling test cycles. The
diamagnetic shift is on the order of 6 to 8 milli-Gauss. This is weaker than
with prior discoveries, due to a lower volume fraction (VF) of superconductive
material within the bulk. The straight lines illustrate the average of the
noise component, skewing apart at Tc.
Above is a plot showing a Meissner
transition near 44 C for the compound Tl5Ba4SiCu8O16+.
Because of its higher volume fraction, it has a stronger transition of around
15 milli-Gauss.
Barium was chosen as
a substitute for both tin (Sn) and lead (Pb) because it is also divalent. It
also adds mass to the upper part of the structure, increasing the planar weight
ratio above that of tin, without lowering the elasticity modulus to the level
of lead. The heavy (upper) region of the unit cell is optimally hole-doped at
25% in the 48C compound.
Of nine unambiguous
magnetization tests, the transitions ranged from a low of 48.0 C up to a high
of 50.2 C. The average of all nine tests was 48.8 Celsius.2 Below
are the two plots with the lowest and highest temperature transitions.
The below graph
shows how Tc has increased in proportion to the planar weight ratio along the
(heavy) C1 axis. Those dots outside the grid are all above room temperature.
These two quinary
compounds were synthesized using the layer cake method, as shown below. The
pellet had over 100 interference layers. And, even using this layering
technique, the volume fraction is low, requiring very sensitive test equipment.
Stoichiometric
ratios of the below chemicals were used for the ODD layers:
Tl2O3 99.99%
(Alfa Aesar) (2.5 or 3 mols)
BaCO3 99.95%
(Alfa Aesar) (4 mols)
CuO
99.995% (Alfa Aesar) (7 or 8 mols)
...and
quasi-stoichiometric amounts of the below for the EVEN layers.
SiO2 99.996%
(GE 214) (7 mols)
CuO
99.995% (Alfa Aesar) (7 mols)
The chemical
precursors were pelletized at 60,000 PSI and sintered for 42 hours at 860C. The
pellet was then annealed for 10+ hours at 500C in flowing O2. Temperature was
determined using an Omega type "T" thermocouple and precision OP77 DC
amplifier. The magnetometer employed twin Honeywell SS94A1F Hall-effect sensors
with a tandem sensitivity of 50 mv/Gauss.
RESEARCH
NOTE: The copper-oxides are strongly
hygroscopic. All tests should be performed immediately after annealing.
RE-PUBLICATION
NOTICE: Elsevier Publishing, dba Elsevier Science, as well as Morris
Communications, both print and broadcast divisions, are specifically prohibited
from re-publishing any part of this news story.
E. Joe Eck
© 2013
Superconductors.ORG
All rights reserved.
1. Materials 5, 6 and 8 have not yet been published, pending patent application.
2. Testing temperatures are believed accurate within +/- 0.50 degrees C.
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