Thermogravimetric Study of MHgO2 (M=Ca, Sr, Ba) under Controlled Oxygen and Mercury Partial Pressures and Related Thermodynamics

The most relevant aspects of thermodynamics, preparation, crystal structure and superconducting properties under ambient and high pressure of HgBa2Can−1CunO2n+2+δ superconductors are reviewed in this contribution. The ideas which inspired authors to search for the new superconductors among Hg-based complex cuprates are discussed as an example illustrating the benefit of the concept of intergrowth structure formation for the design of new layered materials. Recent results on solid–gas equilibriums useful for reproducible syntheses of different homologues are summarized. The crystal structures are discussed with main attention focused on features such as concentration and location of extra oxygen atoms, static atomic displacements due to partial occupation of oxygen site in a Hg-layer, substitution in a Hg position and a presence of stacking faults. It is shown that these factors have to be taken into account for a correct structure description. The relationships between Tc, doping level, amount and formal charge of extra anions and external pressure are outlined to predict possible paths for enhancement of the superconducting properties in complex cuprates.

Section: Fluorination Of Hg-based Superconductorssupporting

confidence: 59%

Section: Synthesis Ofmentioning

confidence: 99%

Chemistry and structure of Hg-based superconducting Cu mixed oxides

Антипов

Abakumov

Putilin

2002

“…The first group, V A Alyoshin et al, investigated equilibrium partial pressures of Hg and O 2 above Hg1201 [34] and MeHgO 2 compounds (Me = Ca, Ba, Sr) [39]. A static weight technique was used for the measurements of the thermodynamics of the following reaction:…”

Section: Equilibrium Partial Pressures Over Hgba 2 Ca N−1 Cu N O 2n+2+δmentioning

confidence: 99%

“…Thermogravimetry under controlled partial mercury P Hg and oxygen P O2 pressures was used for the determination of equilibrium P Hg and P O2 in the threephase equilibrium MHgO 2 (s)-MO(s)-gas of reaction (12) and related thermodynamic calculation [39].…”

Section: Equilibrium Partial Pressures Over Hgba 2 Ca N−1 Cu N O 2n+2+δmentioning

confidence: 99%

High-pressure synthesis, crystal growth, phase diagrams, structural and magnetic properties of Y₂Ba₄Cu_nO_2n+x, HgBa₂Ca_n-1Cu_nO_2n+2+deltaand quasi-one-dimensional cuprates

Karpiński

Meijer

Schwer

et al. 1999

In this paper we present a review of high-gas-pressure single crystal growth studies of YBa2Cu4O8 and Y2Ba4Cu7O15-x performed in oxygen pressure up to 3000 bar and Hg1-xMxBa2Can-1CunO2n+2+ (M = Pb, Re; n = 1-7) compounds in argon pressure up 11 000 bar at temperature up to 1200 °C. Chain compounds A1-xCuO2 (A = Sr, Ca, Ba) have been synthesized at high oxygen pressure up to 2000 bar. High-pressure phase diagram studies of the investigated systems are also discussed. Structure analyses of Y2Ba4CunO2n+x (n = 6-8), Hg1-xMxBa2Can-1CunO2n+2+ (M = Pb, Re; n = 1-8), Sr0.73CuO2 and (Sr,Ca)4Cu6O10 single crystals have been performed. The effects of substitutions and trends in bondlengths are discussed. The vortex state properties of HgBa2Ca2Cu3O8+ and YBa2Cu4O8 single crystals are compared. For Hg-based compounds, the influence of oxygen content, chemical substitutions and radiation defects on vortex pinning were determined. The quasi-one-dimensional cuprates Ca0.83CuO2 and Sr0.73CuO2 show an antiferromagnetically ordered state of long-range 3D character at T < 10 K. The spin dynamics of Sr0.73CuO2, measured by inelastic neutron scattering, indicate that this ordered state coexists with a dimerized singlet ground state.

“…In the course of the synthesis of mercury cuprates, several intermediate phases develop, such as CaHgO 2 , BaHgO 2 or SrHgO 2 whose thermodynamic properties take part in the control of the reaction. The same group have recently developed a very clever instrument that is able to measure the decomposition pressure of these phases [21]. In a differential weight measurement they obtain the amount of Hg released from a mixture of MO/MHgO 2 at a given Hg pressure.…”

Section: Mercuration In Close Quartz Ampoule: In Situ Measurement Of ...mentioning

confidence: 99%

Synthesis of mercury cuprates

Odier¹,

Sin²,

Toulemonde³

et al. 2000

Mercury cuprates have very interesting potential applications that have not been thoroughly explored until now because of the complexity of their synthesis. This paper presents an overview of recent results concerning their processing. At first, a simple sol-gel technique is described that permits one to easily and intimately mix the precursors. The method uses the gelification of an inorganic solution of the cations by acrylamide polymerization. Mercuration of the precursor at moderate pressures (<2-5 MPa) is then discussed. The control of the total pressure during the synthesis by a simple method is shown, and this enables one to quantify some important parameters of the synthesis and to optimize the superconducting properties. This method has been also used successfully to incorporate mercury into layers of precursors and then to form thick layers of superconducting (Hg, Re)-1223, c-axis oriented. Finally, mercuration at higher pressures (up to 6 GPa) is considered and the case of the double mercury layer Hg-2212 is discussed in connection with the oxygen content of the reactants.