Origin of the difference between the high and low-Tc phases in the yttrium sesquicarbide system

摘要: The fabrication conditions of a high-pressure synthesis using BN crucible have been established for the high-Tc (Tc>14?K) and low-Tc (Tc<12?K) phases yttrium sesquicarbide (Y2C3). single-phase sample was synthesized from an arc-melted precursor. In contrast, Y2C3 samples made powder precursor were not single-phase, although reproducibilities phase highest value Tc higher.The refinement results neutron diffraction data high- indicate small difference between two in interatomic distance C?C dimer, while lattice parameter constant all samples. values dTc/dP measured (Tc?15?K) (Tc?11?K) by clamp cell technique detecting AC susceptibility sample. systematically changes with applied hydrostatic pressure both phases. However, trends dTc/dPs are opposite: is positive, that negative. From these results, we concluded our did originate simple contraction unit cell, but distances dimers.