Material Specification for Hg:121; [Hg-Ba-Cu-O]
Process: Solid State Reaction
Notes: "The superconducting sample... was prepared from the solid state reaction of HgO (99.998% pure, Johnson Matthey) with a Ba2CuO3 precursor. To synthesize this precursor, stoichiometric amounts of Ba(NO3)2 (99.999% pure, Johnson Matthey) and CuO (99.999% pure, Johnson Matthey) were mixed together in a sapphire mortar and reacted at 930 °C for 48 h in flowing O2 with one intermediate grinding. Since Ba2CuO3 reacts with moisture, all subsequent handling of the material was done in a glove box utilizing nitrogen gas. A mixture of HgO and Ba2CuO3 was then pelletized under (about) 0.8 GPa pressure and sealed in a thick-walled quartz tube (7 mm I.D., 10 mm O.D.) under (about 0.1 mPa = 10-6 torr) vacuum. The quartz tube was enclosed in a stainless steel container and welded shut as an additional protection against a possible rupture of the quartz tube... Superconducting samples were obtained either by rapid heating (10-15 K/min) to 800 °C or by inserting the sample into a preheated furnace; slow heating (10 h to 800 °C) resulted in a severe reaction of the sample with the quartz tube and yielded non-superconducting samples. Reaction at either 800 °C or 845 °C for 5-8 h followed by an oven cool to ambient temperature resulted in superconducting samples. The sample used in the present high pressure study was then annealed at 200 °C for 12 h in flowing O2."
Formula: HgBa2CuO4+x
Informal Name: Hg:121
Chemical Family: Hg-Ba-Cu-O
Chemical Class: Oxide
Structure Type: Polycrystalline
Manufacturer: In House
Commercial Name: In House
Production Date:
Lot Number:
Production Form:
Density (mass) for Hg:121; [Hg-Ba-Cu-O]
Measurement Method: X-ray diffraction
"The X-ray powder diffraction pattern (CuKα radiation) for the present sample is consistent with a tetragonal unit cell..." No additional measurement details were noted.
Cautions: Unevaluated Data
Crystallography for Hg:121; [Hg-Ba-Cu-O]
| Crystal System: | Tetragonal |
| Formula Units per Cell: | |
| Space Group: |
P4/mmm
|
Cell Parameters
|
Temp
K
|
a
Å
|
b
Å
|
c
Å
|
| 296 |
3.875(1) |
-- |
9.516(1) |
Measurement Method: X-ray diffraction
"The X-ray powder diffraction pattern (CuKα radiation) for the present sample is consistent with a tetragonal unit cell..." No additional measurement details were noted.
Cautions: Unevaluated Data
Critical Temperature for Hg:121; [Hg-Ba-Cu-O]
| Pressure (GPa) |
Tc(upper) (K) |
Critical Temperature (K) |
| 0.0 |
98.1 |
95.0 |
| 0.2 |
98.3 |
95.2 |
| 0.4 |
98.8 |
95.7 |
| 0.5 |
99.0 |
95.9 |
| 0.6 |
99.1 |
96.1 |
| 0.7 |
99.3 |
96.3 |
| 0.8 |
99.5 |
96.5 |
| 0.9 |
99.6 |
96.6 |
Measurement Method: Ac susceptibility
"The He-gas three-stage compressor system used in the present experiments was acquired from Harwood Engineering (Walpole, Massachussetts) and connected via a CuBe capillary tube to a cylindrical (28 mm O.D. x 7 mm I.D.) CuBe pressure cell from Unipress (Warsaw, Poland). The pressure vessel was inserted into a cryostat with a full liquid nitrogen shield and cooled indirectly by exchange gas. All changes in pressure were carried out at a temperature above the melting curve of He (56 K at 0.9 GPa). A nonmagnetically wound wire heater on the pressure cell allowed one to vary the temperature. The AC susceptibility was measured using a standard primary/secondary coil system with a 2.0 mm I.D. cylindrical sample space. An EG&G Model 5210 two-phase lock-in amplifier set at 500 Hz was used to simultaneously measure the in-phase... and out-of-phase... components." The susceptibility is reported for zero pressure in a field of 7.9 A/m = 0.1 Oe.
Cautions: Evaluated Data
"Upon cooling (the susceptibility) shows a slight but sharp break from the horizontal at a temperature T
c (upper)....This initial decrease...clearly marks a superconducting onset, perhaps arising from a small region (about 3%) of the sample which is nearly optimally doped. The primary transition to superconductivity for the bulk of the sample appears to occur below T
c(lower) where (the susceptibility) begins to fall rapidly and trace out a characteristic S-shaped curve." Digitized data were obtained from Figure 3 of the paper.
Magnetic Susceptibility for Hg:121; [Hg-Ba-Cu-O]
| Temperature (K) |
Magnetic Susceptibility (arbitrary) |
| 80 |
-13.6 |
| 90 |
-12.0 |
| 92 |
- 8.0 |
| 93 |
- 4.0 |
| 95 |
- 0.4 |
| 96 |
- 0.3 |
| 98 |
- 0.2 |
| 99 |
0.0 |
Measurement Method: Ac susceptibility
"The He-gas three-stage compressor system used in the present experiments was acquired from Harwood Engineering (Walpole, Massachussetts) and connected via a CuBe capillary tube to a cylindrical (28 mm O.D. x 7 mm I.D.) CuBe pressure cell from Unipress (Warsaw, Poland). The pressure vessel was inserted into a cryostat with a full liquid nitrogen shield and cooled indirectly by exchange gas. All changes in pressure were carried out at a temperature above the melting curve of He (56 K at 0.9 GPa). A nonmagnetically wound wire heater on the pressure cell allowed one to vary the temperature. The AC susceptibility was measured using a standard primary/secondary coil system with a 2.0 mm I.D. cylindrical sample space. An EG&G Model 5210 two-phase lock-in amplifier set at 500 Hz was used to simultaneously measure the in-phase... and out-of-phase... components." The susceptibility is reported for zero pressure in a field of 7.9 A/m = 0.1 Oe.
Cautions: Evaluated Data
"Upon cooling (the susceptibility) shows a slight but sharp break from the horizontal at a temperature T
c(upper)... This initial decrease...clearly marks a superconducting onset, perhaps arising from a small region ( (about) 3%) of the sample which is nearly optimally doped. ... The primary transition to superconductivity for the bulk of the sample appears to occur below T
c(lower) where (the susceptibility) begins to fall rapidly and trace out a characteristic S-shaped curve."
Digitized data were obtained from Figure 1 and Figure 1 (inset) of the paper.
