ENHANCEMENT OF T-C ONSET IN (GA,HG)SR-2(Y,CA)CU2O7 BY HG DOPING

We synthesized a new 1212-type cuprate (Ga1-xHgx)Sr-2(Y1-yCay)Cu2O7. P artial substitution of divalent Hg for trivalent Ga simplifies the syn thesis conditions of the 1212 compound and enhances its T-conset up to 88 K. Similar to GaSr2(Y,Ca)Cu2O7, its structure is orthorhombic of s pace group Ima2. The lattice parameters are in the order of 6a(p)Xb(p) root 2Xc(p) root 2, (p refers to a primitive perovskite). No phase tr ansition (orthorhombic --> tetragonal; large unit cell --> reduced uni t cell) was observed when varying the ratios Ga:Hg and/or Y:Ca.