Role of polarization evolution in the hysteresis effect of Pb-based antiferroelecrtics

The electric field-induced irreversible domain wall motion results in a ferroelectric(FE) hysteresis. In antiferroelectrics(AFEs), the irreversible phase transition is the main reason for the hysteresis effects, which plays an important role in energy storage performance. Compared to the well-demonstrated FE hysteresis,the structural mechanism of the hysteresis in AFE is not well understood. In this work, the underlying correlation between structure and the hysteresis effect is unveiled in Pb(Zr,Sn,Ti)O_(3) AFE system by using in-situ electrical biasing synchrotron X-ray diffraction. It is found that the AFE with a canting dipole configuration, which shows a continuous polarization rotation under the electric field, tends to have a small hysteresis effect. It presents a negligible phase transition, a small axis ratio, and electric field-induced lattice changing, small domain switching. All these features together lead to a slim hysteresis loop and a high energy storage efficiency. These results offer a deep insight into the structure-hysteresis relationship of AFEs and are helpful for the design of energy storage material.

Laser-assisted synthesis of PtPd alloy for efficient ethanol oxidation

The inefficiency of ethanol oxidation reaction(EOR)presents a significant obstacle in harnessing renewable biofuels with high energy density into electricity.Despite efforts,most Pt-based catalysts still suffer from drawbacks such as poor activity and susceptibility to CO poisoning,particularly in acidic conditions.Herein,we employed a physical laser-assisted approach to synthetize a PtPd alloy with a 1:1 atomic ratio.This alloy demonstrates remarkable performance in acidic EOR,boasting a high mass activity of 1.86 A·mgPt^(−1)and competitive resistance to poisoning.Combining in situ synchrotron radiation infrared spectroscopy with theoretical calculations,we reveal that the synergic interaction between Pt and Pd enhances both the adsorption of OH*intermediate and the dehydrogenation ability of ethanol.This work will prove the feasibility of synthesizing bimetallic alloys by a physical laser-assisted strategy and promote the development of advanced alloy electrocatalysts.

Hard and tough novel high-pressure γ-Si_(3)N_(4)/Hf_(3)N_(4) ceramic nanocomposites

Cubic silicon nitride(-Si_(3)N_(4))is superhard and one of the hardest materials after diamond and cubic boron nitride(cBN),but has higher thermal stability in an oxidizing environment than diamond,making it a competitive candidate for technological applications in harsh conditions(e.g.,drill head and abrasives).Here,we report the high-pressure synthesis and characterization of the structural and mechanical properties of a γ-Si_(3)N_(4)/Hf_(3)N_(4) ceramic nanocomposite derived from single-phase amorphous silicon(Si)-hafnium(Hf)-nitrogen(N)precursor.The synthesis of the-Si_(3)N_(4)/Hf_(3)N_(4) nanocomposite is performed at~20 GPa and ca.1500 ℃ in a large volume multi anvil press.The structural evolution of the amorphous precursor and its crystallization to-Si_(3)N_(4)/Hf_(3)N_(4) nanocomposites under high pressures is assessed by the in situ synchrotron energy-dispersive X-ray diffraction(ED-XRD)measurements at~19.5 GPa in the temperature range of ca.1000-1900℃.The fracture toughness(K_(IC))of the two-phase nanocomposite amounts~6/6.9 MPa·m^(1/2) and is about 2 times that of single-phaseγ-Si_(3)N_(4),while its hardness of ca.30 GPa remains high.This work provides a reliable and feasible route for the synthesis of advanced hard and tough-Si_(3)N_(4)-based nanocomposites with excellent thermal stabililty.