Over 15 MA/cm2 of critical current density in 4.8 µm thick, Zr-doped (Gd,Y)Ba2Cu3Ox superconductor at 30 K, 3T

Abstract

An Advanced MOCVD (A-MOCVD) reactor was used to deposit 4.8 µm thick (Gd,Y)BaCuO tapes with 15 mol% Zr addition in a single pass. A record-high critical current density (Jc) of 15.11 MA/cm2 has been measured over a bridge at 30 K, 3T, corresponding to an equivalent (Ic) value of 8705 A/12 mm width. This corresponds to a lift factor in critical current of ~11 which is the highest ever reported to the best of author’s knowledge. The measured critical current densities at 3T (B||c) and 30, 40 and 50 K, respectively, are 15.11, 9.70 and 6.26 MA/cm2, corresponding to equivalent Ic values of 8705, 5586 and 3606 A/12 mm and engineering current densities (Je) of 7068, 4535 and 2928 A/mm2. The engineering current density (Je) at 40 K, 3T is 7 times higher than that of the commercial HTS tapes available with 7.5 mol% Zr addition. Such record-high performance in thick films (>1 µm) is a clear demonstration that growing thick REBCO films with high critical current density (Jc) is possible, contrary to the usual findings of strong Jc degradation with film thickness. This achievement was possible due to a combination of strong temperature control and uniform laminar flow achieved in the A-MOCVD system, coupled with optimization of BaZrO3 nanorod growth parameters.

Engineering current density over 5 kA mm−2 at 4.2 K, 14 T in thick film REBCO tapes

“…A high density of vertically-aligned BZO nanorods along the c-axis and the presence of RE 2 O 3 precipitates along the ab plane have been observed as homogeneously distributed over the whole film cross-section, with the selected micrographs being representative of the entire areas examined by TEM. We attribute such a uniform and continuous growth of BZO nanorods along the c-axis, without any interruption from RE 2 O 3 precipitates over the entire 4.3 μm of thickness, to the high level of temperature and flow control in A-MOCVD [40][41][42]. This finding is different from that of the 3.2 μm thick 20 mol% Zr added GdYBCO film made in three passes by conventional MOCVD by our group, in which the length of the BZO nanorod was found to be reduced with increasing REBCO layer thickness and a low density of thick and short BZO nanorods was observed at the 100-200 nm interface between two passes [35].…”

“…Recently, we have explored the feasibility of utilizing A-MOCVD for growing thick Zr doped REBCO films optimized for in-field performance at intermediate temperatures (30-50 K) and fields, which is the operating regime of interest for applications such as motors and generators [42]. The results of this study have demonstrated that growth of very thick films without deterioration of J c or texture is possible even in the presence of high volume density of BaZrO 3 nanorod precipitates.…”

“…The results of this study have demonstrated that growth of very thick films without deterioration of J c or texture is possible even in the presence of high volume density of BaZrO 3 nanorod precipitates. Remarkably, a high critical current density (J c ) of 15.11 MA cm −2 was achieved in a 4.8 μm thick 15 mol% Zr doped REBCO film, at 30 K, 3 T (  B c), deposited in a single pass [42].…”

“…The multi-pass approach was used in order to curb severe degradation in J c with thickness (>1 μm). However, the multi-pass technique significantly complicates the process [35,[39][40][41][42], which poses significant problems for scale-up to long length production.…”

“…An advanced MOCVD (A-MOCVD) system was developed under the ARPA-E grid-scale rampable intermittent dispatchable storage program, aimed at overcoming the main issues identified in conventional MOCVD reactors, including the J c degradation with thickness [40]. The reactor utilizes direct ohmic heating of a suspended substrate tape, highly laminar flow and rapid tape temperature control using non-contact light pipe temperature monitoring, which when combined, enabled us to grow high performance thick REBCO films with and without dopants [40][41][42]. Previously, over 1500 A/12 mm critical current was achieved in 4.4 μm thick undoped REBCO on an ion beam assisted deposition MgO/LMO substrate in a single pass deposition using an A-MOCVD system [35].…”