Fatigue-less relaxor ferroelectric thin films with high energy storage density via defect engineer

Thin film capacitors with excellent energy storage performances,thermal stability and fatigue endurance are strongly desired in modern electrical and electronic industry.Herein,we design and prepare lead-free0.7Sr_(0.7)Bi_(0.2)TiO_(3)-0.3BiFeO_(3)-x%Mn(x=0,0.5,1.5,2,3)thin films via sol-gel method.Mn ions of divalent valence combine with oxygen vacancies,forming defect complex,which results in marked decline in leakage current and obvious enhancement in breakdown strength.A high energy storage density~47.6 J cm^(-3)and good efficiency~65.68%are simultaneously achieved in 2%Mn doped 0.7Sr_(0.7)Bi_(0.2)TiO_(3)-0.3 BiFeO_(3)thin film capacitor.Moreover,the 2%Mn-doped thin film exhibits excellent thermal stability in wide operating temperature range(35–115℃)and strong fatigue endurance behaviors after 108 cycles.The above results demonstrate that 2%Mn-doped 0.7Sr_(0.7)Bi_(0.2)TiO_(3)-0.3 BiFeO_(3)thin film capacitor with superior energy storage performances is a potential candidate for electrostatic energy storage.

Recent progress of ecofriendly perovskite-type dielectric ceramics for energy storage applications

Increasing concern has been focused on the search for ecofriendly dielectric ceramics to meet the extensive demands of pulsed capacitors.Due to the advantages of high-energy storage density,efficiency,and excellent temperature stability,optimization of energy storage performance in dielectric ceramics has been a goal in the past decades.This review summarizes the recently reported progress in energy storage properties of typical perovskite-type lead-free ceramics.The advantages and shortcomings in the various kinds of ceramics are discussed.Finally,future prospects are presented to provide some guidelines for the exploration of new materials.

Temperature-insensitive KNN-based ceramics by elevating O-T phase transition temperature and crystal texture

The inferior temperature stability of piezoelectric response is the main drawback of KNN-based ceramics.Here,the Ba-doped 0.97(K0.48Na0.52)(Nb0.96Sb0.04)O3-0.03Bax(Bi0.5Ag0.5)1-xZrO3(abbreviated as KNNSBxBAZ)textured ceramics were prepared by the template grain growth(TGG)method.Excellent comprehensive properties(d33¼(406±15)pC/N,TC=274℃,strain is 0.17%)were achieved in KNNSBxBAZ textured ceramics with x=0.2.Meanwhile,its piezoelectric and strain properties also show superior temperature stability(d33 maintained within±20%change in awide temperature range from 25℃to 200℃and strain variation was less than 5%in the temperature range from room temperature to 165℃).The high O-T phase transition temperature(TO-T is 110℃)induced by incorporating Ba ions accounts for the enhanced temperature stability of piezoelectric properties.In addition,the crystal texture always maintains the contribution of piezoelectric anisotropy to the piezoelectric properties during elevated temperature,which significantly improved the temperature stability of piezoelectric properties.This work provides an effective strategy for simultaneously achieving high piezoelectric response and excellent temperature stability in KNN-based ceramics.

Microstructures and Dielectric Properties of Ba_(1-x)Sr_xTiO_3 Ceramics Doped with B_2O_3-Li_2O Glasses for LTCC Technology Applications

Ba1-xSrxTiO3 ceramics, doped with B2O3-Li2O glasses have been fabricated via a traditional ceramic process at a low sintering temperature of 900 ℃ using liquid-phase sintering aids. The microstructures and di- electric properties of B2O3-Li2O glasses doped Ba1-xSrxTiO3 ceramics have been investigated systemat- ically. The temperature dependence dielectric constant and loss reveals that B2O3-Li2O glasses doped Ba1-xSrxTiO3 ceramics have di？usion phase transformation characteristics. For 5 wt% B2O3-Li2O glasses doped Ba0.55Sr0.45TiO3 composites, the tunability is 15.4% under a dc-applied electric field of 30 kV/cm at 10 kHz; the dielectric loss can be controlled about 0.0025; and the Q value is 286. These composite ceramics sintered at low temperature with suitable dielectric constant, low dielectric loss, relatively high tunability and high Q value are promising candidates for multilayer low-temperature co-fired ceramics （LTCC） and potential microwave tunable devices applications.

Excellent energy storage performance of niobate-based glass-ceramics via introduction of nucleating agent

For glass-ceramics, how to realize the collaborative optimization of BDS and permittivity is the key toimprove the energy storage density. In this work, ZrO2 is introduced into BPKNAS glass-ceramics asnucleating agent to promote crystal development of glass-ceramics and then achieve high permittivity.When 1.5 mol% ZrO2 is added, the glass-ceramics have the highest permittivity (~128.59) and meanwhilepossess high BDS (1948.90 kV/cm) due to the dense microstructure. Therefore, BPKNAS-1.5ZrO2 glass-ceramics has the highest theoretical energy storage density (21.62 J/cm3). Moreover, the permittivityvariation of BPKNAS-1.5ZrO2 glass-ceramics is less than 6 % in the wide temperature range from 80 to300 C, showing excellent temperature stability. In addition, BPKNAS-1.5ZrO2 glass-ceramics possessesultrahigh power density, which reaches up to 382.40 MW/cm3 in overdamped circuit. The above evi-dence shows that BPKNAS-1.5ZrO2 glass-ceramics with ultrahigh energy storage density and powerdensity is very competitive in the field of energy storage applications.

High depolarization temperature and superior piezoelectric performance with complex structural evolution in BiFeO_(3)-PbTiO_(3)-(Sr0.7Bi0.2,0.1)TiO_(3) systems

Bismuth ferriteebased ferroelectric ceramics are considered strong competitors in highetemperature piezoelectric applications that benefits from their high depolarization temperature(Td),but problems of large conductivity and low piezoelectric coefficient(d33)should be tackled.BiFeO_(3)ePbTiO_(3)ex(Sr0.7Bi0.2,0.1)TiO_(3)(BFePTexSBT)ternary system are designed in this work that successfully resolves this tough paradox.Rietveld refinements show that this system exhibits multiphase coexistence with complex structural transition among rhombohedral,tetragonal and pseudocubic phase.Interestingly,a high Td~320℃ and d33~236℃/N are synergistically optimized in x=0.20 composition near pseudoephase boundary,which are indicated by multiescale techniques(phase structure,dielectric analysis etc.).What'smore,dual electrostrain peaks appear at separate phase boundaries for x=0.20 and 0.66 compositions with distinct piezo/ferroelectric properties.Rayleigh law and piezoelectric force microscopy analysis clarify that the optimal electrostrain performance for both critical compositions are dominated by intrinsic(x=0.20)and extrinsic(x=0.66)contributions,respectively.This work not only provides a new BFePTexSBT system with a high Td and superior d33 that are promising candidates in highetemperature actuator and sensor applications,but also presents a possibility of multiphaseecoexistence established exotic macroscopic performances.

Polypyrrole random-coil induced permittivity from negative to positive in all-organic composite films

Percolating composites with negative permittivity can be promising candidates for metamaterials.Herein,novel all-organic composite films containing of random coil polypyrrole(PPy)and poly(-vinylidene fluoride)(PVDF)are fabricated via a solution casting method.The random coil PPy is prepared by oxidative template assembly approach for the first time.The experimental result indicates that the negative permittivity is easily adjusted through controlling the random coil PPy contents.Especially,the random coil PPy contents exceeded 7 wt% the negative permittivity appear attributed to the formation of 3D interconnected PPy network.This facile approach not only opens a new way to preparing negative permittivity of all-organic composite films,but also points out a route to facilitate the practical applications of metamaterials.

RELAXOR FERROELECTRIC MATERIALS FOR MICROWAVE TUNABLE APPLICATIONS

With strong dependences of dielectric constant on external applied electric fields,relaxor barium zirconium titanate(BaZr_(x)Ti_(1-x)O_(3)or BZT)and barium stannate titanate(BaS_(n)xTi_(1-x)O_(3)or BTS),in both bulk ceramic and thinfilm forms,are increasingly being recognized as potential candidates of microwave tunable materials for device applications.This paper is aimed to review the recent progress in understanding the dielectric properties(such as tunability,dielectric loss and dielectric constant)of these relaxor materials.However,due to their relatively high dielectric constant and loss tangent,pure Ba(Zr,Ti)O_(3) and Ba(Sn,Ti)O_(3) do not fully satisfy the requirements of practical device applications.Therefore,various strategies have been developed to improve the dielectric properties of these two groups of relaxor materials.In this paper,wefirst discussed the dielectric tunability characteristics of pure Ba(Zr,Ti)O_(3) and Ba(Sn,Ti)O_(3) and then summarized the strategies that have been used,including(i)small amount acceptor or donor doping(such as rare-earth ions and transition metal ions)and(ii)forming composites with low loss and low dielectric constant microwave dielectric materials(such as MgO,MgTiO_(3) and so on).At the same time,the relationship between relaxor behavior and dielectric tunability was also discussed.