Material Specification for TlBa:1212; [Tl-Ba-Ca-Cu-O]
Process: Solid State Reaction
Notes: "... single crystals were grown from melts Tl2O3, CaO, BaO, and CuO. Starting compositions of dry 99.9% or better oxides were prepared... These oxide powders were mixed, ground and sieved through a 300 µm mesh, the process repeated and they were loaded into a 2.5 cm x 2 cm diameter Pt crucible. A tight fitting Pt lid was wired in place. The crucible was loaded into a vertical tube furnace with a quartz liner under (0.1 MPa = 1 atm) of oxygen. For a typical growth run, the crucible was rapidly heated (5 min) to 950 °C by moving the crucible into a preheated furnace and held there for 1 hour. The temperature was then lowered over a period of 12.5 h to 700 °C and then to 25 °C in 5-6 h. Initial temperatures below 900 °C did not produce crystals. The crucible contained a shiny black melt consisting of many plate-like growths. Upon breaking, the melt pockets contained well-formed platelets from 1 mm to 3 mm on a side and 0.01 mm or less thick."
Formula: TlBa2CaCu2O7
Informal Name: TlBa:1212
Chemical Family: Tl-Ba-Ca-Cu-O
Chemical Class: Oxide
Structure Type: Single Crystal
Manufacturer: In House
Commercial Name: In House
Production Date:
Lot Number:
Production Form:
Crystallography for TlBa:1212; [Tl-Ba-Ca-Cu-O]
| Crystal System: | Tetragonal |
| Formula Units per Cell: | |
| Space Group: |
P4/mmm
|
Cell Parameters
|
Temp
K
|
a
Å
|
b
Å
|
c
Å
|
| 296 |
3.8566(4) |
-- |
12.754(2) |
Atomic Coordinates
| Atom |
Temp
K
|
a-axis |
b-axis |
c-axis |
| Tl |
296 |
0 |
0 |
0.5 |
| Tl(D) |
296 |
0.108(2) |
0 |
0.5 |
| Ca |
296 |
0.5 |
0.5 |
0 |
| Ba |
296 |
0.5 |
0.5 |
0.2842(1) |
| Ba(D) |
296 |
0.5 |
0.5 |
0.337(4) |
| Cu |
296 |
0 |
0 |
0.1255(2) |
| O1 |
296 |
0.5 |
0 |
0.1210(8) |
| O2 |
296 |
0 |
0 |
0.342(1) |
| O3 |
296 |
0.5 |
0.5 |
0.5 |
Measurement Method: X-ray diffraction
"A small crystal (0.10x0.15x0.1 mm) was selected... Cell dimensions were determined from 24 different hkl values with 2θ values between 30° and 35°... MoKα intensity data (1043 hkl values) were collected at room temperature on a Nicolet automated diffractometer, corrected for absorption (transmission factors 0.105-0.610), reduced to structure factors and averaged... yielding 166 unique averaged reflections. The heavy atom positions were determined from a Patterson function. Least-squares refinements together with Fourier synthesis determined the details of the crystal structure."
Cautions: Evaluated Data
Tl(D) and Ba(D) denote displaced atom positions in the table of atomic coordinates.
Critical Temperature for TlBa:1212; [Tl-Ba-Ca-Cu-O]
| Critical Temperature (K) |
| 103 |
Measurement Method: Rf penetration method
The authors cite M. Maeda et al., Jpn. J. Appl. Phys., Vol. 27, 2 (1988), and summarize the procedure as follows. "The superconducting transition temperatures of the crystals were routinely determined with an RF penetration technique. Prior experience has shown that the highest temperature appearance of the superconducting signal determined by this technique coincides with the onset of superconductivity determined by static magnetization."
Cautions: Evaluated Data
