Generation of Sr2Ca(n-1)CunOy phases (n = 5-7) by high pressure synthesis

Abstract

We prepared Sr2Ca(n-1)CunOy (n = 3-7) phases using a high-pressure apparatus. In the Sr-Ca-Cu-O system, the n = 5-7 members of a homologous series, Sr2Ca(n-1)CunOy, were prepared as mixed phases for the first time. The c-axis length increases linearly with increasing n; c = 6.46(n-1) + 14.3 Å. Half of this slope gives reasonable value of 3.2 Å as the thickness of a Ca and CuO2 plane. It is likely that a 0(Sr)2(n-1)n phase is formed from a 0(Sr)2(n-2)(n-1) phase to intercalate CaCuO2 into its infinite layer because the number of CuO2 planes increases with increasing sintering temperature and synthetic time. Too high temperature and too long synthesis time result in the formation of the infinite layer phase.

High-pressure synthesis and superconducting properties of Sr2(Ca1− xSrx)Cu2Oy (x = 0–0.75)

“…The 02(n − 1)n series of the Sr-Ca-Cu-O [3][4][5][6][7][8][9][10] and Ba-Ca-Cu-O systems [11][12][13][14][15][16][17][18] have been synthesized and investigated by various groups. The discovery of superconductive 02(n − 1)n compounds with n = 2-4 3,4) in the Sr-Ca-Cu-O system was crucial for deriving the concept of homologous series.…”

“…All members in the 02(n − 1)n series were synthesized at a high-pressure of ∼5 GPa. [3][4][5][6][7][8][9][10] The 02(n − 1)n series are unique because of their capability to absorb H 2 O or CO 2 molecules in the unit cell. 8) The H 2 O or CO 2 molecules are considered to intrude between double-layered (AO) 2 in the Sr 2 Ca [11][12][13][14][15][16][17][18] when they are exposed to moisture-containing air.…”

Organic molecule intercalation sites in Sr2CaCu2Oy superconductor

“…However, it is meaningful to reproduce the c-parameter elongation upon the water molecule intercalation between SrO layers in a 0 (Sr) 212 crystal to form the derivative phase. 7,9 MOPAC simulation was carried out to successfully explain the c-parameter elongation by water intercalation of 0 (Sr) 212 crystal.…”

“…There are numerous cuprate high T c superconductors with various compositions and structures. In the Sr-Ca-Cu-O system, [1][2][3][4][5][6] Sr 2 Ca (n − 1) Cu n O y (0 (Sr) 2(n − 1)n) (n = 1-7) 7,8 phases are known as the crystal structures without charge reservoir layers and synthesized only under high pressures around 5 GPa. In addition, by exposure to moist air, the c-parameters of 0 (Sr) 2(n − 1)n (n = 2-4) 9 crystals are elongated and derivative phases are formed.…”

“…In addition, by exposure to moist air, the c-parameters of 0 (Sr) 2(n − 1)n (n = 2-4) 9 crystals are elongated and derivative phases are formed. 10,11 The elongation of c-parameters are considered to be caused by the intercalation of water molecules into the two SrO layers which are alkaline earth double layers. Similar derivative phase formation was also reported in Ba 2 Ca 2 Cu 3 O y (0 (Ba) 223) [12][13][14][15][16] and in clay minerals including halloysite.…”