Material Specification for Ho:123; [Ho-Ba-Cu-O]
Process: Solid State Reaction
Notes: "Large, single crystals were prepared by employing the citrate-gel process to produce an intimate mixture of very pure barium carbonate, copper oxide and holmium oxide with particle size ≤ 1 µm. A cation ratio of 1:4:10 (Ho:Ba:Cu) was chosen as the flux composition and charges of... 10 g were heated to 1040 °C in high-purity alumina crucibles. Slow cooling rates (between 0.4 °C/h and 20 °C/h) were employed over various temperature ranges to produce the crystals. All operations were carried out under a flow of oxygen of high purity... The largest crystals successfully extracted from the flux have masses > 10 mg but the one selected for this investigation had a mass of 5.3 mg. The crystal was mounted onto an aluminium pin with Kwikfill adhesive so that the [001] axis was approximately in the horizontal plane."
Formula: HoBa2Cu3O7-x
Informal Name: Ho:123
Chemical Family: Ho-Ba-Cu-O
Chemical Class: Oxide
Structure Type: Single Crystal
Manufacturer: In House
Commercial Name: In House
Production Date:
Lot Number:
Production Form:
Crystallography for Ho:123; [Ho-Ba-Cu-O]
| Crystal System: | Tetragonal |
| Formula Units per Cell: | |
| Space Group: |
P4/mmm
|
Cell Parameters
|
Temp
K
|
a
Å
|
b
Å
|
c
Å
|
| 115 |
3.8598(2) |
-- |
11.6537(9) |
| 20 |
3.8592(3) |
-- |
11.647(1) |
Measurement Method: Neutron diffraction
"The crystal was mounted on the D19 diffractometer of the Institute Laue-Langevin (IL-L) which is fitted with a large (64° x 4°) position-sensitive detector. The wavelength used for most of the experiment was... 1.3162 σ. ...The crystal was cooled...with a two-state Displex cryorefrigerator, the crystal quality was checked and an orientation matrix obtained based, on 21 (reflections), from which the corresponding unit-cell parameters were derived. Intensity data were collected ... with a standard (reflection) (006) repeated very 50 (reflections). Data analysis was performed with the IL-L program RETREAT which integrates reflections through use of the PEAKINT program."
Cautions: Evaluated Data
Critical Temperature for Ho:123; [Ho-Ba-Cu-O]
| Critical Temperature (K) |
| 91.5 |
Measurement Method: Rf flux exclusion
"The crystal was placed within a resonant circuit consisting of a small, single-layer coil of copper wire with a parallel silver mica capacitance and driven by a tunnel diode biassed in its negative resistance regime, all at low temperatures. The self-resonance of the RF circuits used were in the 10-20 MHz region and their frequencies were measured with a precision of 1 Hz. As the crystal changed its magnetic properties in moving from the normal to the superconducting state as its temperature was brought below T
c, so the exclusion of flux caused the self-inductance of the coil to fall and the resonant frequency of the LC tank circuit to rise."
Cautions: Evaluated Data
Critical Current Density for Ho:123; [Ho-Ba-Cu-O]
| Temperature (K) |
Critical Current Density (kA/cm2) |
| 4 |
85 |
| 5 |
69 |
| 8 |
32 |
| 12 |
18 |
| 15 |
10 |
| 21 |
4 |
| 27 |
0 |
Measurement Method: Vibrating sample magnetometer
"DC magnetisation measurements of the crystal were made with a vibrating sample magnetometer... the... field... is applied at an angle of 11° to the c-axis. A sweep rate of 6 mT s
-1 was employed between fixed fields with a waiting time of 300 s at each field (approximately 95% of the creep is completed in this time). The detecting lock-in amplifier had a time constant of 1 s and a 12 db/oct. low-pass output filter... The critical currents (were) deduced from the remanent magnetization using the Bean model..."
Cautions: Evaluated Data
Digitized data were obtained from Figure 5 of the paper.
