The superconducting “copper/carbonate cuprates” An electron microscopy study

Unconventional Hall effect in orientedCa3Co4O9thin films

“…20,21 It should be pointed out here that the induced pressure is biaxial, in contrast to what is obtained in the case of hydrostatic pressure already published. In addition, it is well known in these systems that there exists a relaxation of the strains along the thickness which can also broaden the whole result.…”

Oxyanions in perovskites: from superconductors to solid oxide fuel cells

“…26,27 These oxyanions were also shown to be able to take the place of carbonate in the Ba 4 YCu 2+x O y (CO 3 ) z systems producing compounds such as Ba 4 YCu 2.37 O 7.85 (SO 4 ) 0.5 . 28 Further carbonate doping work investigated a range of alternative superconducting cuprate systems, and it was shown that carbonate could also be incorporated into other layered superconducting cuprates, such as (Cu, C)Ba 2 Ca 3 Cu 4 O 11+δ , which has a high T c of 117 K. [29][30][31][32] This example is another case of the observation of unexpected carbonate stabilisation, since the discovery originated from the attempt to prepare an Ag containing analogue of a Hg based superconductor. This phase represents the highest T c for a sample not containing a toxic metal, such as Hg, Tl, and moreover the T c could be increased to 136 K under pressure (21 GPa).…”

High-Pressure Synthesis of Homologous Series of High Critical Temperature (Tc) Superconductors

“…The high-pressure technique allowed an even wider variety of oxycarbonates to be discovered. The (Cu,C)Ba 2 Ca n -1 Cu n O 2 n +3 [(Cu,C)-12( n -1) n -Ba, n = 3, 4] and (Cu,C) 2 Ba 3 Ca n - 1 Cu n O 2 n +5 [(Cu,C)-23( n -1) n -Ba, n = 3, 4, 5] series of superconductors are typical examples of high-pressure stable oxycarbonates. − The former series has BaO−(Cu,C)O−BaO as a charge reservoir. The partial occupation of copper in the middle plane is crucial for hole doping because BaO−CO−BaO has formal charge of 2+ and no holes are thus created.…”

“…The (Cu,C)Ba 2 - 5] series of superconductors are typical examples of high-pressure stable oxycarbonates. [35][36][37][38] The former series has BaO-(Cu,C)O-BaO as a charge reservoir. The partial occupation of copper in the middle plane is crucial for hole doping because BaO-CO-BaO has formal charge of 2+ and no holes are thus created.…”

“…For both (Cu,C)-1223-Ba and (Cu,C)-1234-Ba, electron microscope observations showed superlattices of a s ) 2a, b s ) b, c s ) 2c with respect to simple tetragonal lattices. 35,38 These results are due to ordering of copper and carbon in the (Cu,C) plane; they are placed as Cu-C-Cu-C... along the a-axis resulting in the double periodicity of 2a. In an adjacent (Cu,C) plane, the phase of the Cu-C sequence is different as in C-Cu-C-Cu..., causing double periodicity along the c-axis (Figure 5).…”