Material Specification for Tl:221; [Tl-Ba-Cu-O]
Process: Solid State Reaction
Notes: The authors cite Y. Shimakawa et al., Physica C, Vol. 157, 279 (1989), and summarize the procedure as follows. "A powder sample... was synthesized..."
Formula: Tl2Ba2CuO6.14
Informal Name: Tl:221
Chemical Family: Tl-Ba-Cu-O
Chemical Class: Oxide
Structure Type: Polycrystalline
Manufacturer: In House
Commercial Name: In House
Production Date:
Lot Number:
Production Form:
Crystallography for Tl:221; [Tl-Ba-Cu-O]
| Crystal System: | Tetragonal |
| Formula Units per Cell: | |
| Space Group: |
I4/mmm
|
|
Cell Parameters
| ΔP295K (GPa) |
Temp
K
|
a
Å
|
b
Å
|
c
Å
|
| 0.034 |
60 |
3.85109(4) |
-- |
23.0983(4) |
| 0.149 |
60 |
3.85108(3) |
-- |
23.0990(3) |
| 0.264 |
60 |
3.85092(4) |
-- |
23.0985(4) |
| 0.379 |
60 |
3.85081(3) |
-- |
23.0982(4) |
| 0.527 |
60 |
3.85065(3) |
-- |
23.0973(4) |
| 0.621 |
60 |
3.85063(3) |
-- |
23.0974(4) |
Measurement Method: Neutron diffraction
"Time-of-flight neutron powder diffraction measurements were performed... using the Special Environment Powder Diffractometer (SEPD) at Argonne's Intense Pulsed Neutron Souce (IPNS)... with the sample in a helium gas pressure cell... The pressure cell was cooled by a 12 W Displex closed cycle helium refrigerator... The primary goal of the data collection schedule was to obtain structural data at a pressure of 0.609 GPa and a temperature of 60 K after bringing the sample to this point in pressure-temperature space via six different paths. Pressure was first applied at room temperature to reach the desired value (ΔP
295K). The cell was then cooled to 60 K at a rate of about 1.3 K/min. A decrease in pressure of about 25% was typically observed during cooling due to thermal contraction of the helium gas. After equilibrating the temperature at 60 K (within ±1°) the pressure was increased to 0.609 GPa."
Cautions: Evaluated Data
"The crystal structure at 0.609 GPa and 60 K depends systematically on the path in pressure-temperature space by which these conditions are achieved. Applying pressure at room temperature and then cooling produces different changes in the structure than cooling first and then applying pressure. We speculate that this unusual behavior may be associated with differences in the mobility of interstitial oxygen defects between room temperature and 60 K and that applying pressure at room temperature changes the state of the sample through such processes as defect ordering, while changing the pressure at low temperature does not."
