Effect of alkali metal carbonate A2CO3 (A = Li, Na, K) on AC susceptibility and superconducting properties of YBa2Cu3O7−δ
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The effect of alkali metal carbonate (A2CO3)x addition on YBa2Cu3O7−δ with A = K, Na and Li for x = 0, 0.3, 0.5 and 1.0 wt% has been investigated. XRD patterns showed a single YBa2Cu3O7−δ phase for all samples. The resistance versus temperature measurements showed that all samples exhibited metallic normal state behavior. The addition of Li2O3 suppressed the superconductivity of YBa2Cu3O7−δ more than Na2CO3 and K2CO3. The AC susceptibility measurements showed a decrease in Tcχ′ for Li2CO3 addition. Tcχ′ was not much affected with Na2CO3 and K2CO3 addition which was around 93–94 K for x = 0–1.0 wt%. However, Tcχ′ was very much suppressed in the Li2O3-added samples with Tcχ′ decreasing from 94 K for x = 0 to 83 K for x = 1.0 wt%. The peak temperature Tp of the imaginary part of the susceptibility χ″ shifted to lower temperatures for Li2CO3, Na2CO3 and K2CO3 addition. This indicated the intergranular coupling and flux pinning force were suppressed when alkali metal carbonate was added. This work also showed that alkali metals with smaller ionic radius, Li, suppressed superconductivity of YBa2Cu3O7−δ more than the larger ionic radius, Na and K.
This research was supported by the Ministry of Education of Malaysia under Grant no. FRGS/1/2017/STG02/UKM/01/1.
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Conflict of interest
All authors declare no conflict of interest regarding this paper.
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