“…They are (i) the precursor method in which samples are prepared from a mixture of HgO and Ba-Ca-Cu-O precursor, 8,9 (ii) single-step firing method starting from a mixture of monoxides (HgO, BaO, CaO, and CuO), [10][11][12] (iii) the two-pellet technique in which an Hg-Ba-Ca-Cu-O pellet and a Ba-Ca-Cu-O pellet are placed in a quartz tube, 13,14 (iv) high pressure synthesis technique, 15,16 etc. They are (i) the precursor method in which samples are prepared from a mixture of HgO and Ba-Ca-Cu-O precursor, 8,9 (ii) single-step firing method starting from a mixture of monoxides (HgO, BaO, CaO, and CuO), [10][11][12] (iii) the two-pellet technique in which an Hg-Ba-Ca-Cu-O pellet and a Ba-Ca-Cu-O pellet are placed in a quartz tube, 13,14 (iv) high pressure synthesis technique, 15,16 etc.…”