Transport critical current density of melt textured YBa2Cu3O7−x rods prepared by zone melting using a high temperature gradient

Abstract

We have developed a quasicontinuous crucible free zone melting method for texturing YBCO bulk material. Dense sintered rods with a length of 10 cm were partially molten in the hot zone of a 5 zone furnace and recrystallized in the large temperature gradient (140 °C/cm) limiting this zone. Suitable additions of Y2BaCuO5 (20 mol %) and PtO2 (1 wt %) to the starting material and a growth rate of not more than 1 mm/h were necessary to obtain stable growth conditions. After natural grain selection we obtained 8-cm-long rods with a uniform orientation of the crystallographic axes within 2°. The angle between c direction and rod axis typically was 55°. The critical current density at 77 K measured with continuous current over a length of 4.5 cm was 1.3×104 A/cm2 in zero field and 8×103 A/cm2 in 0.5 T. These values confirm the absence of grain boundaries.

Field percolation and high current density in 80/20 DyBa2Cu3O7 − x/Dy2BaCuO5 bulk magnetically textured composite ceramics

“…We propose to understand the data with the following equation: . This is far away from the record high critical current value (10 6 A/cm 2 at 77 K) in neutron irradiated YBCO single crystals, [21] but much above that of epitaxial thin films [22], of grain aligned YBCO, [23] and other zone melt YBCO with also some 211 excess particles [24].…”

Growth mechanism in the crystallization of YBa2Cu3O6+δfrom peritectic melts

“…Large single crystals of YBa 2 Cu 3 O 6+δ (referred to as 123) are needed for a wide variety of applications from magnetic levitation (maglev) to magnetic shielding [1][2][3][4][5][6]. Even though millimetre size plates of 123 have been grown from hightemperature solutions, large c-axis oriented single crystals of 123 have been difficult to obtain [7][8][9] primarily due to certain limitations of the high-temperature solution growth technique generally employed to grow the single crystals [3,[6][7][8][9][10][11][12][13][14][15][16][17].…”

“…Large single crystals of YBa 2 Cu 3 O 6+δ (referred to as 123) are needed for a wide variety of applications from magnetic levitation (maglev) to magnetic shielding [1][2][3][4][5][6]. Even though millimetre size plates of 123 have been grown from hightemperature solutions, large c-axis oriented single crystals of 123 have been difficult to obtain [7][8][9] primarily due to certain limitations of the high-temperature solution growth technique generally employed to grow the single crystals [3,[6][7][8][9][10][11][12][13][14][15][16][17]. Melt growth has not been possible due to the peritectic melting of YBa 2 Cu 3 O 6+δ (which results in the formation of Y 2 BaCuO 5 (generally referred to as the 211 phase)+liquid (BaCuO 2 +CuO solution)), which reverts on solidification to 123 + 211 + other phases (solidified BaCuO 2 , CuO) [5,10,13,14,16,[18][19][20][21].…”

“…Even with extremely high cooling rates it has not been possible to obtain single phase 123 single crystal from stoichiometric melts [23]. However, the 211 and other phases present in the melt-textured 123 have been found to enhance J c (the critical current density) and flux trapping, by acting as pinning centres, and thus to be advantageous for applications like shielding and maglev [1][2][3][4][5][6]. Therefore various methods have been proposed to grow a large grain (it is called large grain and not a single crystal as it contains 211 and other phases) of 123 material from peritectic melts.…”

“…Therefore various methods have been proposed to grow a large grain (it is called large grain and not a single crystal as it contains 211 and other phases) of 123 material from peritectic melts. All of them employ some kind of directional solidification either by moving the furnace or the molten material to eventually obtain a single grain material [3,5,7,8]. In the present work we have used the peritectic crystallization technique to grow a large oriented grain of 123 material and have investigated the peritectic growth mechanism through a variety of experimental methods.…”