Synthesis and Superconductivity of the Ternary Hydrides (Th,Y)H₁₀

Recent achieved superconductivity near room temperature, especially in hydrogen-based superconductors under high pressure, have attracted broad interest. However, most systems with high superconducting critical temperature (T_c) are only stable under extremely high pressures, which limits their practical applicability. This study proposes the possibility of obtaining high-T_c superconductors at moderate pressures within the ternary Th-Y-H system. The synthesis was carried out using Th, YH₃, and NH₃BH₃ as precursors under high pressure and high temperature, applied by diamond anvil cells combined with in-situ laser heating technology. Combining with the synchrotron X-ray diffraction (XRD) measurements and theoretical studies, the main product was identified as Fm $\overline{3}$m (Th,Y)H₁₀, with Y accounting for approximately 10%−15%. Electrical transport measurements reveal that its T_c increases by approximately 10%, compared to ThH₁₀ under similar pressure. At 144 GPa, the sample has a maximum T_c of 184 K, which remains at 170 K when decompressed to 100 GPa—approaching the highest level known for hydrides at this pressure. Measurements under an applied magnetic field further verify the superconductivity, with upper critical fields estimated at 52 and 39 T based on the WHH and GL models, respectively. These results indicate that the ternary Th-Y-H superconducting system is an outstanding candidate for high-T_c superconductors, and the crystal stability and electronic properties can be effectively controlled by reasonably introducing new element into the binary system. This work provides new insights and experimental evidences for exploring high-T_c superconducting hydrides under moderate or even low pressures.