AbstractPhase 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 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 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.
Ferroelectric phase-transition frustration near a tricritical composition point
