Growth Of Nanodomains Research Articles

Strain glass transition in Ni47.5+xTi50−xFe2.5 alloys

There have been limited studies on the influence of the Ni/Ti ratio on the strain glass transition behavior in NiTiFe shape memory alloys. In this study, Ni47.5+xTi50−xFe2.5 (x = 0, 0.5, 1.0) alloys were prepared and their microstructural evolution, dynamic mechanical properties, and temperature-dependent electrical resistivity were investigated. We find that increasing Ni/Ti ratio in Ni48.5Ti49Fe2.5 alloy could suppress the long-range martensitic transformation, resulting in the occurrence of strain glass transition characterized by the continuous formation and growth of nanodomains. As a result, a successive softening in elastic modulus and the negative temperature coefficient of electrical resistivity in a broad temperature range have been observed.

Evolution of Nanodomains and Formation of Self-Organized Structures during Local Switching in X-Cut LNOI

The features of nanodomain growth during local switching in X-cut lithium niobate on insulator (LNOI) were comprehensively studied using the biased tip of a scanning probe microscope. The obtained results were discussed in terms of the kinetic approach. The revealed differences in domain growth in bulk LN and LNOI were attributed to the higher bulk conductivity of LNOI. The obtained influence of humidity on the shape and growth of isolated domains was attributed to the water meniscus. Analysis of the transition between the “forward growth” and “sideways growth” stages was performed by switching to the stripe electrode. A sand-glass-shaped domain was formed due to growth in the opposite direction after the domain touched the electrode. Stable periodical domain structures down to 300 nm were created and characterized in LNOI. Highly ordered comb-like domains of various alternating lengths, including four- and eight-fold increase periods, were produced by performing biased tip scanning along the Y axis. The obtained knowledge is important for the future development of nanodomain engineering methods in monocrystalline ferroelectric thin films on insulators.

Large piezoelectricity and potentially activated polarization reorientation around relaxor MPB in complex perovskite

Improving piezoelectric performance is always favorable to further enhance the sensitivity and accuracy of piezoelectric devices. Here, a complex piezoelectric system of Pb(Ni1/3Nb2/3)O3-Pb(Yb1/2Nb1/2)O3-Pb(Hf0.1Ti0.9)O3 is designed and investigated in detail. Optimized piezoelectric response of ∼ 880 pC/N is achieved at the composition of 0.51PNN-0.09PYN-0.40PHT. The characterization of TEM and In-situ high-energy synchrotron diffraction indicate that nanodomain growth and microdomain switching occurs in succession at around coercive electric field. Most interestingly, the coexisted tetragonal and rhombohedral-like phase transforms into multiple monoclinic-like phases with polarization vectors aligned as close to the electric field direction as possible under the strong electric field. The enhanced polarization instability in this complex morphotropic phase boundary sample should be ascribed to the strong local heterogeneity. The novel polarization rotation behavior found in this work would be important guidance for designing high-performance piezoceramics.

Local and Average Structure of Yb-Doped Ceria through Synchrotron and Neutron Pair Distribution Function

As transport properties of doped ceria electrolytes depend significantly on the nature of the dopant and the defectivity, the design of new materials and devices requires proper understanding of the defect structure. Among lanthanide dopants, Yb shows some peculiar characteristics that call for a possible different defect structure compared to Gd and Sm conventional dopants, which could be linked to its poorer performance. For this purpose, we combine synchrotron and neutron powder diffraction exploiting the Rietveld and Pair distribution Function. By increasing its concentration, Yb produces qualitatively the same structural distortions as other dopants, leading to a domain structure involving the progressive nucleation and growth of nanodomains with a Yb2O3-like (C-type) structure hosted in a fluorite CeO2 matrix. However, when it comes to growing the C-type nanodomains into a long-range phase, the transformation is less pronounced. At the same time, a stronger structural distortion occurs at the local scale, which is consistent with the segregation of a large amount of oxygen vacancies. The strong trapping of VOs by Yb3+ explains the poor performance of Yb-doped ceria with respect to conventional Sm-, Gd-, and Y-doped samples at equal temperature and dopant amount.

Studying processes of crystallization and cation ordering in Eu2Hf2O7

Methods of local X-ray anomalous diffraction and X-ray absorption spectroscopy based on the interaction of synchrotron radiation with condensed matter have been used to study the processes of formation and evolution of the crystal structure in Eu2Hf2O7 powders. It has been shown that the isothermal annealing of the X-ray amorphous mixed hydroxide leads initially to the formation of nanocrystalline powders, which have a defect fluorite structure with a clearly pronounced nonequivalence of the local environment of the Eu3+ and Hf4+ cations. An increase in the temperature of heat treatment to ≥1200°C leads to the nucleation and growth of nanodomains with a superstructural cation ordering of the pyrochlore type inside the coarse crystallites of the defect fluorite and, finally, at T ≥ 1500°C, to the complete phase transition of the fluorite-pyrochlore type in the Eu2Hf2O7 system. In the pyrochlore Eu2Hf2O7 structure, there was for the first time revealed a simultaneous broadening of the shape of the L3 absorption edges of both hafnium and europium, which indicates a partial change in the symmetry of the nearest oxygen environment of both cations.

Short- and long-range order balance in nanocrystalline Gd2Zr2O7 powders with a fluorite-pyrochlore structure

A series of nanocrystalline Gd2Zr2O7 powders has been studied using a combination of X-ray diffraction and X-ray spectroscopy with synchrotron radiation. It has been shown that isothermal annealing of an X-ray amorphous mixed hydroxide first leads to the formation of an oxide nanomaterial with a defect fluorite structure and clearly pronounced nonequivalence of the local environment of the Gd3+ and Zr4+ ions. Increasing heat treatment temperature results in initiation and growth of nanodomains with pyrochlore-type superstructure ordering of cations inside bulkier crystallites of defect fluorite. To adequately describe the evolution of the real nanocrystalline structure of gadolinium zirconate, a combination of X-ray structural methods sensitive to the averaged crystal structure and local atomic structure should be used.

Kinetics of nanodomain growth in ferroelectric artificial superlattices

We report the kinetics of nanoscale domain growth in ferroelectric PbZrO3/PbTiO3 artificial superlattices. Ferroelectric superlattices behave as single ferroelectric materials with only 180° domain structure (monodomain). Domain size increases linearly with the pulse voltage, and is linearly dependent on the logarithmic value of the pulse duration. It was found that ferroelectric superlattices have a relatively high activation field for domain growth and enhanced domain stability, resulting in a long-term retention behavior of more than one month.