High pressure synthesis of Hg-1234 and strongly-overdoped Hg-1223 phases

Crystal Growth and Characterization of HgBa2Ca2Cu3O8+δ Superconductors with the Highest Critical Temperature at Ambient Pressure

“…[6][7][8][9][10] These very useful techniques have shown their efficiency to obtain the phases with a high n number of CuO2 layers (n ≥ 4). [11][12][13][14][15] Because of the complexity of its compounds chemistry, considerable difficulties remain in growing single crystals of mercury cuprates and separating them from the flux. 11,16,17,18,19 Indeed the compounds undergo incongruous melting and decompose at low oxygen pressure, having low thermal and chemical stability.…”

“…The first impediment in preparing the mercury-based cuprates lies in the toxicity of mercury oxide (HgO) and the volatility of its decomposition product, namely, mercury, which occurs near 450 °C in air, before the mercury-containing superconducting phases are formed. Therefore, the first synthesis route used to produce pure phases was via a solid-state reaction in a sealed tube, − but the pure calcium-containing phase ( n ≥ 2) was obtained only with difficulty; high-pressure techniques have been shown to prevent HgO decomposition and to facilitate formation of the desired products. − These very useful techniques have shown their efficiency for the synthesis of the phases with a high n number of CuO 2 layers ( n ≥ 4). − Because of the complexity of its compound chemistry, considerable difficulties remain in growing single crystals of mercury cuprates and separating them from the flux. ,− Indeed, the compounds undergo incongruous melting and decompose at low oxygen pressure, having low thermal and chemical stability.…”

Establishment of strongly overdoped states in theHgBa2Ca2Cu3Fujinami1, Itô2, Suematsu3 et al. 1997Phys. Rev. B22060View full textAdd to dashboardCite

“…The decrease in T c seems to correlate with the decrease in both the cell parameters a and c. The decrease in the a parameter, i.e., the shortening of the in-plane Cu-O bond, originates from the removal of antibonding electrons from the CuO 2 planes, 35 while incorporation of excess oxygen atoms into the HgO ␦ charge-reservoir block is supposed to shorten the distance between the Ba and HgO ␦ planes, and thereby be seen as a shortening of the c axis. 28 Lokshin et al 36 describe the high-pressure synthesis of overdoped Hg-1223 samples using BaO 2 as an oxygen generator. In Fig.…”

Layered Cuprates Containing Flat Fragments: High-Pressure Synthesis, Crystal Structures and Superconducting Properties

“…Crystal structures of corresponding members of Au and Hg-series are rather similar (except for the first member), however, there are some important differences. First, maximum T c was achieved in the Hg-series but not in the Au-series [ 26 , 29 ]. Moreover, only first four members of Au-series were identified in comparison with six members of Hg-series (the n = 7 member was obtained only if doped in the Hg site).…”