3 PHASES IN THE SYSTEM HG1-XCXBA2CUOY ESS-THAN-OR-EQUAL-TO-X-LESS-THAN-OR-EQUAL-TO-1.00)

Samples of the [Hg1-xCx]-Ba(2)CuOy system [(Hg,C)-1201] with stoichiom etries within the range 0.00 less than or equal to x less than or equa l to 1.00 were synthesized by a high-pressure, high-temperature techni que. The sample with x = 0.00 [HgBa2CuO4+delta] was non-superconductin g with lattice parameters a = 3.8676(2) Angstrom, c = 9.470(1) Angstro m. At low ranges of substitution (0.10 less than or equal to x less th an or equal to 0.30), the predominant phase was found to be Hg-1201 wi th identical lattice parameters to those found for x = 0.00. At x = 0. 40 the Hg-1201 phase coexists in similar proportions with the phase of mixed [Hg-1-x,C-x]-1201 stoichiometry. At x = 0.50, this second phase with lattice parameters a = 3.9271(3) Angstrom, c = 8.676(2) Angstrom is predominant and only traces of the Hg-1201 phase were found. At x = 0.75 the [Hg-1-x,C-x]-1201 phase found for x = 0.50 coexists with th e CO3Ba2CuOy phase, which is the extreme of the substitution range. Th is latter was predominant at x = 1.00 with lattice parameters a = 4.00 44(3) Angstrom, c = 7.909(1) Angstrom, but at higher pressure than the previous substitutions. This system is constituted of three main phas es, HgBa2CuO4+delta, Hg1-xCxBa2CuOy (x = 0.50) and CO3Ba2CuOy, which a ppear in different proportions according to the percentage of substitu tion and the applied synthesis pressure.