STABILIZATION OF 3 NEW OXYCARBONATES BY V-SUBSTITUTION AND CR-SUBSTITUTION - THE SUPERCONDUCTORS (TL,M)(1)SR4CU2(CO3)O-7 (M=CR, V) AND (HG,V)(1)SR4CU2(CO3)O-6+Z

Three new superconducting oxycarbonates have been synthesized. The tetragonal phase Hg0.6V0.4Sr4Cu2(CO3)O-6+z, (a = 3.850 Angstrom, c = 16.240 Angstrom), is isotypic with the carbonates (Hg,M)(1)Sr4Cu2(CO3)O-6+z (M = Mo, Cr) previously synthesized: it consists of a single intergrowth of the Sr2CuO2(CO3)(S2CC) and 1201 structures; this S2CC-1201 oxycarbonate has the highest T-c's observed for mercury oxycarbonates: 76 K. The orthorhombic phases Tl2/3Cr1/3Sr4CU2(CO3)O-7 (a = 5.418 Angstrom, b = 27.108 Angstrom, c = 16.668 Angstrom) and Tl0.8V0.2Sr4Cu2(CO3)O-7 (a = 5.401 Angstrom, b = 27.076 Angstrom, c = 16.628 Angstrom) exhibit a (110)-collapsed S2CC-1201 structure; their structure derives from the classical S2CC-1201 intergrowth by a shearing mechanism with (11O)(S2CC-12O1) as shearing plane: the structure is translated by c/2 every five octahedra alternately along (110)(p) or (110)(S2CC-1201). These compounds represent the first pure strontium collapsed oxycarbonates, showing that the presence of barium is not necessary for the appearance of a shearing in the S2CC-1201 structure. Both are superconductors, but the Cr phase has the highest T-c (77 K) that has been observed up to date in these oxycarbonates, whereas the V phase has a much lower T-c (50 K).