Superconductivity is achieved in Nd 1−x Ce x OBiS 2 via electron doping using mixed-valence Ce ions. Single crystals with x = 0.2, 0.3, 0.4, and 0.5 are generated using a CsCl flux method. Plate-like single crystals with dimensions of 0.8×0.8×0.2 mm 3 were obtained. The magnetic susceptibility χ(T ) indicates large diamagnetism, and the electrical resistivity ρ(T ) indicates zero resistivity. The maximum value of T c is observed at 4.7 K in Nd 0.8 Ce 0.2 OBiS 2 from χ(T ). From the ρ(T ) measurements taken in several magnetic fields, the upper critical field µ 0 H c2 (0) is estimated to be ∼12 and ∼0.34 T for the ab-and c-planes, respectively. We redetermined µ 0 H c2 (0) of NdO 0.7 F 0.3 BiS 2 , as ∼35 and ∼0.78 T for the ab-and c-planes, respectively. The anisotropic parameter Γ is estimated to be ∼35 for Nd 0.7 Ce 0.3 OBiS 2 and ∼45 for NdO 0.7 F 0.3 BiS 2 . The µ 0 H c2 (0) of Nd 0.7 Ce 0.3 OBiS 2 is approximately two times smaller than that of NdO 0.7 F 0.3 BiS 2 , although the difference of Γ is approximately 10.
We performed the electrical resistivity and thermoelectric power measurements of the polycrystalline La0.8Ti0.2OBi(S1-xSex)2. The electrical resistivity of La0.8Ti0.2OBi(S0.7Se0.3)2 at room temperature dramatically decreases, and the temperature dependence shows metallic-like behavior. From the electrical resistivity, superconductivity was not observed in La0.8Ti0.2OBi(S1-xSex)2 above 2.8 K. The value of thermoelectric power S(300 K) of La0.8Ti0.2OBiSSe was about -65 μV/K, which is comparable to that of the polycrystalline LaOBiS2. The value of S(300 K) of La0.8Ti0.2OBiS2 was about -115 μV/K. These power factors are relatively smaller than that of the polycrystalline LaOBiSSe.
We investigated the non-doping LaOBiSSe and the hole-doping La 1-x Sr x OBiS 2 by the hydrostatic pressure effect. We measured the temperature dependence of the electrical resistivity of LaOBiSSe within the temperature range of 3-300 K by applying several hydrostatic pressures using a cubic anvil cell. An upturn was observed below 80 K at ambient pressure. The upturn was suppressed up to 2.0 GPa but it re-emerged up to 8.0 GPa. The electrical resistivity of La 1-x Sr x OBiS 2 (x = 0.1, 0.2) showed semiconducting-like behavior under ambient pressure. At pressures lower than 2.05 GPa, the electrical resistivity in the whole range of temperature decreased drastically, but the semiconducting-like behavior was also observed. The sign of the temperature dependence of the thermoelectric power in La 1-x Sr x OBiS 2 was negative below room temperature. The results suggest that the carrier was exactly the electron.
Electrical resistivity of LaO0.5F0.5Bi(S0.9Se0.1)2 have been measured at a temperature range of 2.8 ∼ 300 K by applying several hydrostatic pressures. Pressure-induced superconducting phase was observed above a pressure P of 0.85 GPa and Tc increased from 2.86 K to 8.42 K. The sudden increase of Tc in LaO0.5F0.5Bi(S0.9Se0.1)2 results from the structural phase transition from tetragonal (P4/nmm) to monoclinic (P21/m). Structural phase transition pressure Pc of LaO0.5F0.5Bi(S0.9Se0.1)2 is higher than that of LaO0.5F0.5BiS2. The increase of Pc is ascribed to the suppression of the displacement parameter of the in-plane chalcogen site induced by chemical pressure of Se-substitution.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.