Ferroelectric phase-transition frustration near a tricritical composition point

Phase transition describes a mutational behavior of matter states at a critical transition temperature or external field. Despite the phase-transition orders are well sorted by classic thermodynamic theory, ambiguous situations interposed between the first- and second-order transitions were exposed one after another. Here, we report discovery of phase-transition frustration near a tricritical composition point in ferroelectric Pb(Zr1-xTix)O3. Our multi-scale transmission electron microscopy characterization reveals a number of geometrically frustrated microstructure features such as self-assembled hierarchical domain structure, degeneracy of mesoscale domain tetragonality and decoupled polarization-strain relationship. Associated with deviation from the classic mean-field theory, dielectric critical exponent anomalies and temperature dependent birefringence data unveil that the frustrated transition order stems from intricate competition of short-range polar orders and their decoupling to long-range lattice deformation. With supports from effective Hamiltonian Monte Carlo simulations, our findings point out a potentially universal mechanism to comprehend the abnormal critical phenomena occurring in phase-transition materials.

A facile one-step synthesis of molybdenum carbide-carbon composites for the hydrogenation of naphthalene

A molybdenum carbide-carbon composite (β-Mo2C/C) is prepared by carbonization of an anionic resin with molybdate. The β-Mo2C/C is characterized by X-ray diffraction, N2 physisorption, scanning electron microscopy, and transmission electron microscopy. Characterization indicates that the sample shows a hierarchically microporous, mesoporous, and macroporous structure, and has a large surface area. The nanosized β-Mo2C crystals are highly dispersed in the carbon-based sample. The β-Mo2C/C composite shows high catalytic activity in the hydrogenation of naphthalene to tetralin.

Transmission electron microscopy characterization of low temperature boron doped silicon epitaxial films

Transmission electron microscopy techniques to better understand growth mechanisms and annealing of low temperature silicon epitaxy. HRTEM: thickness measurement, crystal morphology, and defect study. GPA (image processing): strain field analysis.