Electroactive phases of poly(vinylidene fluoride) : determination, processing and applications

Physical Review B

This paper reviews the crystal chemistry, synthesis, densification, microstructure, mechanical properties, and oxidation behavior of zirconium diboride (ZrB2) and hafnium diboride (HfB2) ceramics. The refractory diborides exhibit partial or complete solid solution with other transition metal diborides, which allows compositional tailoring of properties such as thermal expansion coefficient and hardness. Carbothermal reduction is the typical synthesis route, but reactive processes, solution methods, and pre-ceramic polymers can also be used. Typically, diborides are densified by hot pressing, but recently solid state and liquid phase sintering routes have been developed. Fine-grained ZrB2 and HfB2 have strengths of a few hundred MPa, which can increase to over 1 GPa with the addition of SiC. Pure diborides exhibit parabolic oxidation kinetics at temperatures below 1100°C, but B2O3 volatility leads to rapid, linear oxidation kinetics above that temperature. The addition of silica scale formers such as SiC or MoSi2 improves the oxidation behavior above 1100°C. Based on their unique combination of properties, ZrB2 and HfB2 ceramics are candidates for use in the extreme environments associated with hypersonic flight, atmospheric re-entry, and rocket propulsion.

Refractory Diborides of Zirconium and Hafnium

Perovskite lead-free dielectrics for energy storage applications

The aim of this review article on recent developments of mechanochemistry (nowadays established as a part of chemistry) is to provide a comprehensive overview of advances achieved in the field of atomistic processes, phase transformations, simple and multicomponent nanosystems and peculiarities of mechanochemical reactions. Industrial aspects with successful penetration into fields like materials engineering, heterogeneous catalysis and extractive metallurgy are also reviewed. The hallmarks of mechanochemistry include influencing reactivity of solids by the presence of solid-state defects, interphases and relaxation phenomena, enabling processes to take place under non-equilibrium conditions, creating a well-crystallized core of nanoparticles with disordered near-surface shell regions and performing simple dry time-convenient one-step syntheses. Underlying these hallmarks are technological consequences like preparing new nanomaterials with the desired properties or producing these materials in a reproducible way with high yield and under simple and easy operating conditions. The last but not least hallmark is enabling work under environmentally friendly and essentially waste-free conditions (822 references).

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Hallmarks of mechanochemistry: From nanoparticles to technology

High-performance piezoelectrics benefit transducers and sensors in a variety of electromechanical applications. The materials with the highest piezoelectric charge coefficients (d33) are relaxor-PbTiO3 crystals, which were discovered two decades ago. We successfully grew Sm-doped Pb(Mg1/3Nb2/3)O3-PbTiO3 (Sm-PMN-PT) single crystals with even higher d33 values ranging from 3400 to 4100 picocoulombs per newton, with variation below 20% over the as-grown crystal boule, exhibiting good property uniformity. We characterized the Sm-PMN-PT on the atomic scale with scanning transmission electron microscopy and made first-principles calculations to determine that the giant piezoelectric properties arise from the enhanced local structural heterogeneity introduced by Sm3+ dopants. Rare-earth doping is thus identified as a general strategy for introducing local structural heterogeneity in order to enhance the piezoelectricity of relaxor ferroelectric crystals.

https://par.nsf.gov/servlets/purl/10130928

Giant piezoelectricity of Sm-doped Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals.

縦方向電界場中で曲げたpin-pmn-pt単結晶の強度

The full set of material constants for relaxor-based ternary single crystals Pb(In(12)Nb(12))O(3)-Pb(Mg(13)Nb(23))O(3)-PbTiO(3) (PIN-PMN-PT) were determined and compared to binary Pb(Mg(13)Nb(23))O(3)-PbTiO(3) (PMNT) crystals The Curie temperature for rhombohedral compositions of PIN-PMN-PT was found to be in the range of 160-200 degrees C with ferroelectric rhombohedral to tetragonal phase transition on the order of 120-130 degrees C, more than 30 degrees C higher than that found for PMNT The piezoelectric coefficients (d(33)) were in the range of 1100-1500 pCN, with electromechanical coupling factors (k(33)) about 89%-92% comparable to PMNT crystals The coercive field of the ternary crystal was found to be 55 kVcm, double the value of the binary counterparts The dielectric behavior under varying dc bias exhibited a similar trend as observed in PMNT with a much broader usage temperature range Together with its enhanced field induced phase transition level, the ternary PIN-PMN-PT crystals are promising candidates for high temperature and high drive transducer applications

Characterization of Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 ferroelectric crystal with enhanced phase transition temperatures

Relaxor based Pb(In0.5Nb0.5)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 ternary single crystals (PIN-PMN-PT) were reported to have broader temperature usage range (TR-T) and comparable piezoelectric properties to Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMNT) crystals. In this work, the orientation dependent dielectric, piezoelectric and electromechanical properties for PIN-PMN-PT crystals were investigated along ⟨001⟩ and ⟨110⟩ directions. The electromechanical couplings k33 and k32 for ⟨110⟩ poled crystals were found to be 0.91 and 0.91, respectively, with piezoelectric coefficients d33 and d32 on the order of 925 and −1420 pC/N. Of particular significance was the mechanical quality factor Q33 for ⟨110⟩ oriented crystals, which was found to be ≥500, much higher than the Q values of ⟨001⟩ oriented relaxor-PT crystals (Q∼70–200). The temperature dependence of the piezoelectric properties exhibited good temperature stability up to their ferroelectric phase transition TR-T∼125 °C, indicating ⟨001⟩ and ⟨110⟩ oriented PIN-PMN-PT are promising materials for transducer applications, with the latter for high power resonant devices where low loss (high Q) was required.

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Electromechanical characterization of Pb(In0.5Nb0.5)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 crystals as a function of crystallographic orientation and temperature

Nonlinear ceramics that provide the basis for high-energy-density and high-temperature capacitors, as well as tunable microwave dielectrics, and their applications are discussed in this article

Wesley S. Hackenberger

Papers

Giant piezoelectricity of Sm-doped Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals.

縦方向電界場中で曲げたpin-pmn-pt単結晶の強度

Characterization of Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 ferroelectric crystal with enhanced phase transition temperatures

Electromechanical characterization of Pb(In0.5Nb0.5)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 crystals as a function of crystallographic orientation and temperature

Nonlinear dielectric ceramics and their applications to capacitors and tunable dielectrics