Fe-based bulk metallic glasses (BMGs) have attracted great attention due to their unique magnetic and mechanical properties, but few applications have been materialized because of their brittleness at room temperature. Here we report a new Fe₅₀Ni₃₀P₁₃C₇ BMG which exhibits unprecedented compressive plasticity (>20%) at room temperature without final fracture. The mechanism of unprecedented plasticity for this new Fe-based BMG was also investigated. It was discovered that the ductile Fe₅₀Ni₃₀P₁₃C₇ BMG is composed of unique clusters mainly linked by less directional metal-metal bonds which are inclined to accommodate shear strain and absorbed energy in the front of crack tip. This conclusion was further verified by the X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy experiments of Fe_80-xNi_xP₁₃C₇ (x = 0, 10, 20, 30) and Fe_72-xNi_xB₂₀Si₄Nb₄ (x = 0, 7.2, 14.4, 21.6, 28.8) glassy systems. The results also indicate a strong correlation between the p-d hybridization and plasticity, verifying that the transition from brittle to ductile induced by Ni addition is due to the change of bonding characteristics in atomic configurations. Thus, we can design the plasticity of Fe-based BMGs and open up a new possible pathway for manufacturing BMGs with high strength and plasticity.

Two non-centrosymmetric metal chalcogenides, BaCdSnS₄ and Ba₃CdSn₂S₈, were synthesized using a high temperature solid-state reaction in an evacuated silica tube. Although the two compounds have the same building units in their structures, namely CdS₄, SnS₄ and BaS₈ units, both of them have different structures. BaCdSnS₄ crystallizes in the orthorhombic space group Fdd2 and its structure can be characterized by the two-dimensional _∞[Cd–Sn–S] layers composed of corner- and edge-sharing CdS₄ and SnS₄ tetrahedra with Ba atoms located between the two adjacent _∞[Cd–Sn–S] layers. Ba₃CdSn₂S₈ crystallizes in the space group I3d of the orthorhombic system and the CdS₄ and SnS₄ groups are connected with each other via corner-sharing to form a three-dimensional framework, which is different from the 2D _∞[Cd–Sn–S] layer structure in BaCdSnS₄. The UV-vis-NIR diffuse-reflectance spectra show that the experimental band gaps are about 2.30 eV for BaCdSnS₄ and 2.75 eV for Ba₃CdSn₂S₈, respectively. IR and Raman measurement results indicate that their transparent ranges are up to 25 μm. Second-order NLO measurements show that BaCdSnS₄ exhibits strong powder second-harmonic generation (SHG) intensities at 2.09 μm laser pumping that are ∼5 and 0.7 times that of AgGaS₂ in the particle size 38–55 and 150–200 μm, respectively, whereas Ba₃CdSn₂S₈ only exhibits SHG intensities of about 0.8 and 0.1 times that of AgGaS₂ at the same particle sizes. The origin of the NLO response in BaCdSnS₄ may originate from the macroscopic arrangement of the SnS₄ and CdS₄ tetrahedra. Furthermore, the photoluminescence properties of the two compounds have also been investigated and show obvious blue and green light emission.