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To develop a quick method for the preliminarily screening of mutant strains that can accumulate 9α-hydroxyandrost-4-ene-3,17-dione (9α-OH-AD), a high-throughput screening method was presented by applying the principle that 2,4-dinitrophenylhydrazine (DNPH) can react with ketones to produce precipitation. The optimal color assay conditions were the substrate androst-4-ene-3,17-dione (AD) concentration at 2.0 g/L, the ratio of AD to DNPH solution at 1:4, and the sulfuric acid and ethanol solution percentages in DNPH solution at 2% and 35%, respectively. This method was used to preliminarily screen the mutants of Rhodococcus rhodochrous DSM43269, from which the three ones obtained could produce more 9α-OH-AD. This DNPH color assay method not only broadens screening methods and increases screening efficiency in microbial mutation breeding but also establishes a good foundation for obtaining strains for industrial application. [ABSTRACT FROM AUTHOR]

Multiple mechanisms of fatigue crack initiations from pores leading to short-term and long-term fatigue life have been observed in a powder metallurgy (PM) Ti–6Al–4V alloy made by the hydrogen sintering and phase transformations (HSPT) process. The pores in the sintered alloy could be classified into two groups; type-I being caused by particle interstices that did not fully close during sintering (sinter-pores) and the type-II originating from larger voids that did not close during powder packing (cave-pores). The fatigue life trends can be classified by the type and the location of pore from which the crack initiated. Interestingly, the two types of pores, and the two different locations (surface versus interior) from which the cracks initiated lead to four distinct S–N trends in the fatigue data. When the stress amplitude level and the pore size were accounted for through initial stress intensity factors, the fatigue data reduced to dual S–N fatigue curves. The results offer new insights into how pores, especially their type and size, and location control the fatigue behavior of PM Ti–6Al–4V alloy. Large improvements in fatigue life can be obtained if the large cave-pores are eliminated or their volume density reduced to very low levels. [ABSTRACT FROM AUTHOR]

The present study aims at revealing the relationships between hydrogen concentration and phase structure, as well as microstructure modification in the β-metastable β-21S titanium alloy. The β-bcc phase can accommodate a large number of interstitial atoms, and hydrogenation by means of molecular hydrogen gas was employed in the present work. The phase structure as well as the microstructure of this alloy was found to be strongly dependent on hydrogen concentration. At lower hydrogen concentration (H/M ≤ 0.300), the microstructure consisting of the single β-phase revealed that the interstitially dissolved hydrogen atoms expanded the bcc lattice and inhibited the decomposition of the β phase upon cooling. The introduction of hydrogen beyond H/M = 0.300 was found to generate a large amount of internal stresses in the microstructure inducing the formation of metastable phases α'' in the form of lamellae and ω in the form of nanoparticles. The generation of the nanosized ω-phase was presumed to relax the strain caused by the volume expansion (2.28%) from the hydrogen-containing β phase to the α'' martensite. [ABSTRACT FROM AUTHOR]

High polarization of ferroelectric materials has profound research significance and is the decisive factor in the application of energy storage, pyroelectricity, and explosive energy conversion. Herein, in force-electric conversion field, an ultrahigh remanent polarization (51.43 μC/cm2) and record-breaking energy density (4.59 J/cm3) after poling were achieved with a lead-free (1 − x)Bi0.5Na0.5TiO3 − xAgNbO3 [(1 − x)BNT – xAN] relaxor ceramics. The enhancement effect of AgNbO3 on polarization is attributed to the increase in lattice distortion and orientation after poling. Additionally, a significant force-electric conversion effect under hydrostatic pressure (depolarization rate ∼44.8%, 400 MPa) and shock pressure (depolarization rate ∼54.4%, 6.3 GPa) in (1 − x)BNT – xAN was attributed to the pressure-driven ferroelectric/relaxor (FE/RE) phase transition. This work is expected to enlighten the further design of ferroelectric materials with high polarization for pulse power energy conversion application. [ABSTRACT FROM AUTHOR]

Antiferroelectrics (AFE) are considered a promising energy storage material for components that require nanosecond-level discharge. Pb(Yb 1/2 Nb 1/2)O 3 (PYN) is an AFE material with potential energy storage applications. However, the unmatched critical phase transition field (E F) and breakdown electric field (E B) conceal most of energy storage capacitance. This work is aimed to settle imbalanced E F / E B via a compositional design strategy. E F and E B were tuned in order to obtain 5.18 J cm−3 in recoverable energy density, 65% energy efficiency, and thermal and frequency stability varying within 15%, producing excellent comprehensive energy storage properties. A modified kinetic model of energetic path was used to understand the mechanism governing the variation of E F. We expect our work to contribute to further development of novel AFE materials for energy storage. [ABSTRACT FROM AUTHOR]

We report the electric-field-induced ferroelectric (FEIN) to antiferroelectric (AFE) phase transition that is tuned by the poling temperatures in 0.89Bi0.5Na0.5TiO3-0.06BaTiO3-0.05K0.5Na0.5NbO3 (0.89BNT-0.06BT-0.05KNN) ceramics. Phase transition and pyroelectric behaviors of the ceramics were investigated as functions of temperature and electric field. Pyroelectric coefficient peaks of (3 ∼ 6.5) × 10-8 C cm-2 K-1 are detected at about 10 °C above the poling temperatures for the samples poled at different temperatures. The poling temperature tuned pyroelectric behaviors are attributed to the FEIN to AFE phase transition when the temperature increases. [ABSTRACT FROM AUTHOR]

Solid solutions of (1−x)PbZrO3‐xBa(Mg1/3Nb2/3)O3 (PZ‐xBMN, x = 0.02, 0.03, 0.04, and 0.05) were prepared, and their microstructures, electrical properties, and phase transition behaviors under hydrostatic pressure were investigated. It was found that the incorporation of BMN into PZ can provide improved ferroelectric properties, leading to the formation of antiferroelectric/ferroelectric phase boundaries in PZ‐xBMN ceramics when the value of x is between 0.02 and 0.03. It was also demonstrated that the ferroelectric phases exhibit excellent temperature stability in the remanent polarization. Importantly, complete depolarization was observed in the PZ‐xBMN solid solution due to the hydrostatic pressure‐induced ferroelectric‐antiferroelectric phase transition. The resultant properties and phase transition behaviors of PZ‐xBMN ceramics under pressure will benefit their application in pulsed power supplies. [ABSTRACT FROM AUTHOR]

In this work, the effects of composition, temperature, and poling on the phase transition behavior under hydrostatic pressure of lead‐free (1‐x)[(0.98Bi0.5Na0.5Ti0.995Mn0.005O3‐0.02BiAlO3)]‐xNaNbO3 (BNT‐BA‐xNN) ceramics were investigated. It was found that hydrostatic pressure can induce a phase transformation from ferroelectric (FE) to relaxor (RE). Meanwhile, the FE‐RE phase transition pressure (PFR) tends to decrease as the NN addition increases. Moreover, increasing temperature exhibits a similar effect that is, reducing PFR. The reduced PFR were considered to result from the reduced FE stability and increasing proportion of RE phase. However, PFR was obviously enhanced after poling, which can be attributed to the induced FE phase and the formation of macrodomains with application of an electric field. These results will aid in understanding the phase transition behavior of BNT‐based relaxor ferroelectrics for applications under hydrostatic pressure. [ABSTRACT FROM AUTHOR]

Abstract: High pyroelectric performance and good thermal stability of pyroelectric materials are desirable for the application of infrared thermal detectors. In this work, enhanced pyroelectric properties were achieved in a new ternary (1−x)(0.98(Bi0.5Na0.5)(Ti0.995Mn0.005)O3–0.02BiAlO3)–xNaNbO3 (BNT–BA–xNN) lead‐free ceramics. The effect of NN addition on the microstructure, phase transition, ferroelectric, and pyroelectric properties of BNT–BA–xNN ceramics were investigated. It was found that the average grain size decreased as x increased to 0.03, whereas increased with further NN addition. The pyroelectric coefficient p at room temperature (RT) was significantly increased from 3.87 × 10−8Ccm−2K−1 at x = 0 to 8.45 × 10−8Ccm−2K−1 at x = 0.03. The figures of merit (FOMs), Fi, Fv and Fd, were also enhanced with addition of NN. Because of high p (7.48 × 10−8Ccm−2K−1) as well as relatively low dielectric permittivity (~370) and low dielectric loss (~0.011), the optimal FOMs at RT were obtained at x = 0.02 with Fi = 2.66 × 10−10 m/V, Fv = 8.07 × 10−2 m2/C, and Fd = 4.22 × 10−5 Pa−1/2, which are superior to other reported lead‐free ceramics. Furthermore, the compositions with x ≤ 0.03 exhibited excellent temperature stability in a wide temperature range from 20 to 80°C because of high depolarization temperature (≥110°C). Those results unveil the potential of BNT–BA–xNN ceramics for infrared detector applications. [ABSTRACT FROM AUTHOR]

Abstract: The effect of lanthanum (La) content on the phase transformation of Pb1−3x/2Lax(Zr0.42Sn0.40Ti0.18)O3 (PLZST 100x/42/40/18, 0 ≤ x ≤ 0.06) ceramics was investigated by the dielectric and ferroelectric properties. The base composition PLZST 0/42/40/18 located in the ferroelectric (FE) rhombohedral phase region. As x increased, the compositions showed successively FE and antiferroelectric (AFE) state at room temperature, and their peak temperatures (Tmax) decreased gradually in line as Tmax = 162.21‐1507x. Evidence was presented that there were two dielectric anomalies in PLZST 2/42/40/18, which were corresponding to the FE‐AFE and AFE‐paraelectric (PE) phase transformations, respectively. With increasing the dc bias fields, the two phases merged into one. PLZST 3/42/40/18 showed AFE characteristics with the first loop outside of the second loop and there was only one dielectric inflection. The critical lanthanum content occurred at x = 0.03 from the dielectric temperature spectra and hysteresis loops. Furthermore increase in La above 0.03, these compositions showed typical antiferroelectric behaviors with double hysteresis loops. The stored energy properties of the three compositions (PLZST 4/42/40/18, 5/42/40/18 and 6/42/40/18) displayed different temperature dependencies from room temperature to 140°C (over their respective Tmax). Comparing the above results with previous investigations on PLZSTs, some questions were discussed. [ABSTRACT FROM AUTHOR]

Hafnium oxide based ferroelectric (FE) and antiferroelectric (AFE) thin films show great potentials in memory and energy related applications, while their successes in commercially available devices depend strongly on detailed characterization and deep understanding of the endurance properties of the materials. In this work, the bipolar field cycling behavior has been investigated in detail for FE and AFE-like Si-doped HfO 2 films. Their apparent differences in fatigue and breakdown resistance are interpreted by the modified switching-induced charge-injection model. Referring to the first-order phase transition theory, we summarize and predict the evolution of polarization switching characteristic for FE, AFE-like and AFE Si-doped HfO 2 thin films stressed with bipolar field cycling. Additionally, several approaches are suggested to improve the endurance properties of ferroelectric HfO 2 -based thin films in terms of fabrication process and material design. [ABSTRACT FROM AUTHOR]

The temperature scaling relations of the dynamic hysteresis were investigated in Zr-rich lead zirconate titanate (PZT) bulk ceramics. At each relation curve, there is a discontinuous district corresponding to the low- and high-temperature phase transitions. The temperatures are divided into low-T region and high-T region. At each temperature region, three power-law scaling relations were obtained for hysteresis area , coercivity Ec, and remnant polarization Pr with T, respectively. The six temperature scaling relations are field dependent and the simplified forms are different from the results obtained from the soft and hard PZT ceramics. [ABSTRACT FROM AUTHOR]

Pb 0.99 (Sn x Zr 0.95− x Ti 0.05 ) 0.98 Nb 0.02 O 3 (PNZST( x ), 0.10 ≤ x ≤ 0.18) ceramics were fabricated by conventional solid state reaction method. Effects of tin (Sn) doping and its content x on their structure, phase transition behavior, and electrical properties were investigated. Analysis of X-ray diffraction patterns and Rietveld refinement results confirmed the crystal structures of different phases and also compositional driven phase transitions. The results indicated that with the increase in the value of x , orthorhombic phase was transformed into distorted tetragonal phase through rhombohedral phase. Ceramics exhibited the orthorhombic–rhombohedral phase coexistence for 0.10 ≤ x ≤ 0.16, and orthorhombic–rhombohedral–distorted tetragonal multiphase coexistence for x = 0.18. Although the orthorhombic antiferroelectric (AFE) phase was the major phase, no double hysteresis loops were detected through electrical hysteresis loop measurements because the electric field-induced AFE to ferroelectric (FE) phase transition occurred under the applied electric field, and the induced FE phase could not reverse back to AFE state after the removal of electric field. However, the trace of AFE behavior could be observed at a lower testing electric field. Moreover, increasing Sn content led to linear increment in phase transition temperature of FE RL -FE RH , up to 98.7 °C for x = 0.18. [ABSTRACT FROM AUTHOR]

Microstructure, phase transition and electric properties of Pb 0.99 (Zr 0.95 Ti 0.05 ) 0.98 Nb 0.02 O 3 (PZTN 95/5) ferroelectric ceramics modified with x wt% ZnO additive (where x  = 0, 0.1, 0.2, 0.3 and 0.4) were systematically investigated. It was found that ZnO modification brought out an improvement of densification and an increase in grain size of PZTN 95/5 ceramics. Results of dielectric and pyroelectric measurements demonstrated that, the low temperature rhombohedral-high temperature rhombohedral ferroelectric phase transition temperature ( T LH ) gradually decreased with increasing x to 0.2, while the Curie temperature ( T c) gradually increased. With further increasing ZnO content, however, T LH and T C almost showed no change. Additionally, the excellent ferroelectric, pyroelectric and piezoelectric properties were all achieved by less than 0.2 wt% ZnO modification. It is suggested that, due to superior room–temperature pyroelectric properties, the 0.2 wt% ZnO-modified PZTN 95/5 ceramics may be a promising material for applications in uncooled pyroelectric infrared detectors. [ABSTRACT FROM AUTHOR]

In this paper, the influence of phase evolution on polarization change and electrocaloric response in lead-free (Ba0.9Ca0.1)(Ti1− x Zr x)O3 ceramics ( BCTZ) was systematically investigated. With increasing Zr/Ti ratio, the phase structure and phase transition behavior were greatly changed, resulting in various temperature and electric field dependence of electrocaloric responses. For x=0.05, a peak electrocaloric temperature change 1.64 K (at 130°C) and corresponding entropy change 1.78 J·kg−1·K−1 were obtained for 0-7 kV·mm−1 electric field. Negative electrocaloric temperature change in −0.1 K was obtained below Curie temperature ( Tc), which may be induced by the orthorhombic-tetragonal ferroelectric phase transition. With the increase in x, the peak value of the electrocaloric response decreased but much better temperature stability was observed. Simultaneously the negative electrocaloric response gradually disappeared with the disappearance of the low temperature ferroelectric-ferroelectric phase transition. For x=0.2, electrocaloric response showed good temperature stability ranging from room temperature to 130°C, attributing to the relaxor ferroelectric feature. [ABSTRACT FROM AUTHOR]

The composition dependent dielectric, ferroelectric and energy storage properties of tetragonal lead lanthanum zirconate stannate titanate (PLZST) antiferroelectric ceramics were systematically studied in this paper. Two sets of simple linear scaling relations were established for the forward switching field E AFE-FE , the backward switching field E FE-AFE and recoverable energy density W re . As Zr content increases (Ti fixed), E AFE-FE , E FE-AFE , W re decreases linearly, while the stored energy density W st declines first and then increases. In addition, decreasing Ti content (Zr fixed) leads to linear increments in all of E AFE-FE , E FE-AFE , W re and W st . These results not only reveal the superiority of PLZST with lower Zr and lower Ti contents for energy storage capacitors, but also provide a fast way to design PLZST ceramics with specific energy storage properties. Our work may also be very helpful for better understanding the mechanism of phase transition behaviors of antiferroelectric materials. [ABSTRACT FROM AUTHOR]

In this study, we investigated the scaling behavior of dynamic hysteresis with frequency f and electric field E in epitaxial PbZrO 3 antiferroelectric film on (111)-oriented SrTiO 3 substrate. The scaling relation for the saturated hysteresis loops takes the form of hysteresis area ∝ f 0.03 ( E − 499) 0.20 at relatively low testing f . However, when frequency exceeds 30 Hz, the shows stronger dependence on f while remains basically unchanged relation with E , leading to a form of ∝ f 0.10 ( E − 499) 0.20 . The scaling behavior is modeled as occurring in a viscous medium where several forces, such as viscous and restoring forces, act on the phase transition process. [ABSTRACT FROM AUTHOR]

The phase transition behaviors of Pb 0.99 (Zr 0.95 Ti 0.05 ) 0.98 Nb 0.02 O 3 ferroelectric ceramics doped with different MgO concentrations (0–0.2 wt%) were systematically investigated by Raman and dielectric measurements. Raman results showed that the phase transitions were strongly dependent on MgO concentration. It was found that the low temperature rhombohedral (F R(LT) )–high temperature rhombohedral (F R(HT) ) ferroelectric phase transition shifted toward a lower temperature with increasing MgO concentration up to 0.1 wt%, while the F R(HT) –cubic paraelectric (P C ) phase transition changed to a higher temperature. The Raman results were in good agreement with phase transition determined by dielectric measurements. Moreover, it was indicated that the changes of Raman active modes were related to distortion of BO 6 octahedra during the phase transitions. Then, the distortion of BO 6 octahedron caused by B-site replacement of Mg 2+ ions was proposed to explain the observed behaviors. In addition, the effects of MgO doping on the dielectric, ferroelectric and pyroelectric properties were also discussed. [ABSTRACT FROM AUTHOR]

Pure and Nb-doped Pb(Zr 1− x Ti x )O 3 ( x = 0.47, 0.48, 0.50) ceramics were prepared by conventional solid-state reaction technique. Dielectric anomalies are observed in both kinds of samples near room temperature. The anomalies could be depressed by donor doping and prefer to be significant in ceramics with tetragonal crystallographic phase. Phase transition mechanism and domain wall pinning effect are proposed to explain this anomaly, and the former is considered as the dominated reason. Further results of the pyroelectric measurements confirm the existence of the ferroelectric–ferroelectric phase transition. [ABSTRACT FROM AUTHOR]

Abstract: Grain size effect on phase transition, dielectric and pyroelectric properties of BST ceramics under DC bias field was reported for the first time. With the grain size increased by one order of magnitude, phase transition diffuseness parameters δ and γ decreased from 282 to 63 and 1.64–1.33, respectively. This resulted in the dielectric constant maximum increased by 65%, the pyroelectric coefficient maximum and corresponding figure of merit were quadrupled and tripled, respectively. The physical essence of the great size effect can be attributed to a combination of surface effect, mechanical stress effect and extrinsic effect of grain boundary. A well understanding of the grain size effect and its mechanism will be useful for the BaTiO3-based ceramics and other ferroelectrics. [Copyright &y& Elsevier]

Abstract: Dielectric properties of Pb0.99375(Zr0.52Ti0.48)0.9875Nb0.0125O3 (PZTN) ceramics were measured during heating and cooling processes before and after poling. A dielectric anomaly from 220K to 290K was only observed in poled PZTN samples. The frequency dependence of the ε′′ peaks was fitted using the Vogel–Fulcher law, which indicated that this dielectric anomaly could be associated with the poling induced monoclinic distortion. Meanwhile, the existence of the low-temperature transformation involving rotations of the octahedra was confirmed by the broadening peaks in ε′′–T curves and the variation of slopes in ε′–T curves in both unpoled and poled samples. [Copyright &y& Elsevier]

Highlights: [•] The FR(LT)–FR(HT) phase transition was reduced from 41°C to 24°C with MgO addition. [•] Superior pyroelectric properties were obtained in 0.10wt% MgO-modified sample. [•] The largest p of 65×10−8 Ccm−2 K−1 was achieved at room temperature. [•] Fd of 20×10−5 Pa−1/2 and Fv of 0.91m2C−1 were also attained at room temperature. [ABSTRACT FROM AUTHOR]

Abstract: Sr x Ba1−x Nb2O6 (with x=0.50, 0.45, 0.40 and 0.30) ceramics were synthesized by conventional solid-state method and sintered at 1350°C for 3h. The phase structure, microstructure, dielectric, ferroelectric and pyroelectric properties of obtained ceramics were systematically investigated. Pure tungsten bronze phase could be obtained in all ceramics. The dielectric characteristics showed that SBN ceramic was a relaxor with strong diffuse phase transition and weak frequency dispersion. As Sr molar fraction x increases from 0.30 to 0.50, the transition temperature T C decreased linearly while the diffusivity parameter γ declined from 1.88 to 1.68. The saturated polarization, remnant polarization and pyroelectric coefficient were also found to be enhanced in SBN ceramics with increasing Sr content. The pyroelectric coefficient of about 2×10−8 C/cm2K can be obtained for polarized SBN50 ceramics at room temperature. [Copyright &y& Elsevier]

Energy-storage properties of 0.89 Bi0.5Na0.5TiO3-0.06 BaTiO3-0.05 K0.5Na0.5NbO3 (0.89 BNT-0.06 BT-0.05 KNN) lead-free ceramics were first investigated. Measurements of dielectric properties together with switching current curves indicate a rather diffuse ferroelectric ( FE) to anti-ferroelectric ( AFE) phase transition when heating from 20°C to 90°C. The energy density ( W), which was calculated from P-E hysteresis loops, increases linearly with the external electric field when E exceeds AFE- FE transition field. W is independent of temperature and frequency, and maintains around 0.59 J/cm3 under 5.6 kV/mm in the stable AFE phase region. These properties indicate that 0.89 BNT-0.06 BT-0.05 KNN ceramics might be a promising lead-free AFE material for energy-storage capacitor application. [ABSTRACT FROM AUTHOR]

Abstract: A phase diagram for the lead-free ceramics in the (1−x%)(0.89Bi0.5Na0.5TiO3–0.06BaTiO3–0.05K0.5Na0.5NbO3)–x%MnO2 (BNBKN-x%Mn) binary system is constructed for the first time based on the ferroelectric and dielectric measurements. The ferroelectric behaviors under different temperatures suggest that the ceramics are basically of relaxor anti-ferroelectric nature near room temperature. The temperature dependent dielectric properties show that when the addition of MnO2 increases, the relaxor anti-ferroelectric phase can be stabilized to be close to the Curie point, which corresponds to a relaxor anti-ferroelectric to paraelectric phase transition. [Copyright &y& Elsevier]