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High-entropy alloys (HEAs) are new alloys that contain five or more elements in roughly-equal proportion. We present new experiments and theory on the deformation behavior of HEAs under slow stretching (straining), and observe differences, compared to conventional alloys with fewer elements. For a specific range of temperatures and strain-rates, HEAs deform in a jerky way, with sudden slips that make it difficult to precisely control the deformation. An analytic model explains these slips as avalanches of slipping weak spots and predicts the observed slip statistics, stress-strain curves, and their dependence on temperature, strain-rate, and material composition. The ratio of the weak spots’ healing rate to the strain-rate is the main tuning parameter, reminiscent of the Portevin-LeChatellier effect and time-temperature superposition in polymers. Our model predictions agree with the experimental results. The proposed widely-applicable deformation mechanism is useful for deformation control and alloy design.

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Two types of infrared fluoride phosphors, Cr3+-doped K3AlF6 and K3GaF6, were developed in this research. The K3Al1–x F6:xCr3+ and K3Ga1–y F6:yCr3+ fluoride phosphors were proven to be pure phase via X-ray diffraction refinement, which demonstrated that the procedure can be applied to large-scale production. Electron paramagnetic resonance measurements indicated that Cr3+ ions in cubic with respect to noncubic are coupled better with K3GaF6 than with K3AlF6. The main differences between these two phosphors, the site symmetry and pressure behavior of the spectra, were obtained in temperature- and pressure-dependent spectra. According to the calculation results, Cr3+ in fluorine coordination at ambient pressure indicates an intermediate crystal field. For the phosphor-converted light-emitting diodes (LEDs) fabricated from these two phosphors, the spectral range is from 650 to 1000 nm, which resulted in a radiant flux of 7–8 mW with an input power of 1.05 W. The research reveals detailed luminous properties, which will lead to a new way of studying Cr3+-doped fluoride phosphors and their application in LEDs.

New solution processable 3,5-dithioalkyl dithienothiophene (DSDTT) based small molecular semiconductors end functionalized with various (fused) thiophenes including dithienothiophene (DTT), thienothiophene (TT), and thiophene (T) are synthesized and characterized in organic field effect transistors (OFETs). The new DSDTT core was synthesized via a one-pot [1 + 1 + 1] methodology. For comparison, non-thiolated 3,5-dialkyl dithienothiophene (DRDTT) based molecules are also prepared and characterized. Optical, electrochemical, and computed electronic structures of these molecules are investigated and contrasted. Single crystal data support evidence of S­(alkyl)···S­(thiophene) intramolecular locks, with a very short intramolecular S–S distance of 3.17 Å, planarizing the structure as for the equivalent extended n-thienoacenes. Via a solution-shearing semiconductor film deposition method, these semiconductors exhibit a OFET hole mobility up to 2.6 cm2 V–1 s–1, the greatest reported to date for fused/all-thiophene based small molecular organic semiconductors.