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Novel titanium dioxide ceramics containing bismuth and antimony

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Journal of Materiomics 2017年第2期3卷 112-120页

作者： Zhenwei Li jiagang wu Department of Materials Science Sichuan University610064PR China

Here,we developed one kind of novel TiO_(2) ceramics with colossal dielectric constant by chemical modifications(Bi^(3+) and Sb^(5+)),and discussed the physical origin for giant dielectric *** of Bi and/or Sb on their microstructure,dielectric properties as well as its frequency and temperature stability were studied in *** was found that their dielectric properties are strongly sensitive to(Bi,Sb)contents,and colossal dielectric permittivity(CP)(10^(4)~10^(5))together with low dielectric loss(~5.7%)can be obtained in a wide composition *** addition,all the ceramics possessed good frequency(10^(2)~10^(6)Hz)and temperature(-150-200℃)stability of dielectric *** addition,the defects caused by the Bi volatilization may be the reason for higher dielectric properties of(Bi_(0.5)Sb_(0.5))_(x)Ti_(1-x)O_(2) ceramics with respect to(A_(0.5)Sb_(0.5))_(x)Ti_(1-x)O_(2)(A=In,Pr,Dy,Sm,Gd,Yb,Ga,Al,Fe or Sc).According to the results of complex impedance and XPS,the electron-pinned defect-dipoles may be suitable to explain the CP phenomenon,and oxygen vacancies-induced by Bi^(3+)&Sb^(5+) substitution for Ti^(4+) should be responsible for conduction *** believe that this profound investigation can benefit the development of TiO_(2) ceramics as a CP material.

关键词： Colossal permittivity TiO_(2) Antimony and Bi Physical mechanism

Enhanced strain and electrostrictive properties in lead-free BNT-based ceramics via rare earth doping

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Journal of Materiomics 2022年第2期8卷 401-407页

作者： Anping Deng jiagang wu Department of Materials Science Sichuan UniversityChengdu610064China

Bi_(0.5)Na_(0.5)TiO_(3)(BNT)-based ceramics are one of the most promising lead-free ferroelectrics due to their high strain *** to other chemical modifications,rare earth ions doping provides sig-nificant possibility to optimize the strain property of BNT-based *** this work,the effects of rare earth ions on phase structure,microstructure,and strain&electrostrictive properties of lead-free BNT-based ceramics were systematically *** earth ions(i.e.,La^(3+),Sm^(3+),Yb^(3+),Dy^(3+),and Nd ^(3+))were selected as the doping *** moderate La^(3+)ions can drive the ferroelectric state of BNT-based ceramics to nonergodic relaxor state or ergodic relaxor *** enhanced strain response of~0.40-0.42% and high converse piezoelectric coefficient of~600-630 pm/V can be achieved under 60-70 kV/cm for La^(3+)-doped ceramic with nonergodic relaxor ***,the giant electrostrictive coefficient Q 33 of~0.047 m 4/C 2 can be obtained for La ^(3+)-doped ceramic with ergodic relaxor *** rare earth ions also present the promotion effect on strain enhancement for BNT-based *** study affords a significant guidance to optimize strain and electrostrictive properties of BNT-based ce-ramics via rare earth ions doping.

关键词： BNT-based ceramics Rare earth doping Strain property Electrostrictive property Structure transition

Insight into the large electro-strain in bismuth sodium titanate-based relaxor ferroelectrics:From fundamentals to regulation methods

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Journal of Materials Science & Technology 2023年第19期150卷 27-48页

作者： Xiaojun wu Lanji Wen Chao wu Xiang Lv Jie Yin jiagang wu College of Materials Science and Engineering Sichuan University610064PR China

Due to the demand for environmental protection,developing eco-friendly piezoelectric applica-tions/materials is an inevitable *** market share of lead-free materials is growing steadily every *** typical lead-free systems,Bi_(0.5)Na_(0.5)TiO_(3)(BNT)has attracted wide attention due to its supe-rior strain property(e.g.,dynamic piezoelectric coefficient d33*of most modified-BNT ceramics exceeds 600 pm/V,which is higher than commercial soft PZT ceramics PIC151).The excellent strain performance in BNT-based materials is thought to arise from the relaxor-ferroelectric transition,and currently,the mainstream strain regulation method is chemical *** far,amounts of effective dopants have been investigated,while the intrinsic strain regulation mechanism is still ambiguous(e.g.,how do dopants work?).Therefore,we review the intrinsic strain regulation mechanism,and strain origination and reg-ulation methods are also investigated to comprehend the regulation ***,the strain origination and regulation mechanism are investigated from different dimensions(e.g.,macro perspective and micro perspective),which is vacant in previous *** the macro view,the particular tai-lored relaxor-ferroelectric crossover is the critical key for the giant electro-strain,while from the micro view,the electro-strain is dominated by the cracked ferroelectric order and relaxor-ferroelectric transi-tion,resulting from the broken Bi-O bonds due to the local field *** the strain origination and regulation mechanism of BNT-based ceramics is of great importance to exclude the blind researching mode and rationally design the experimental scheme.

关键词： Strain origin Bi_(0.5)Na_(0.5)TiO_(3)(BNT) Strain regulation

Effects of rare-earth dopants on phase structure and electrical properties of lead-free bismuth sodium titanate-based ceramics

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Journal of Materiomics 2020年第2期6卷 286-292页

作者： Anping Deng jiagang wu Department of Materials Science Sichuan UniversityChengdu610064China

In this work,the effects of rare earth(RE)dopants on the phase structure,microstructure,and electrical properties of lead-free bismuth sodium titanate(BNT)-based ceramics were *** earth elements(i.e.,Sm,Gd,Ho,Pr,Y,and Yb)were selected as the dopants to replace the Bi site of Bi_(0.5)(Na_(0.8)K_(0.2))0.5TiO_(3) *** was found that the addition of moderate RE ions reduced the temperature of ferroelectricrelaxor transition(T_(f-r))and the dielectric maximum at lower temperature,while the slight influence on the dielectric maximum at higher temperature and microstructure were ***,the threestage evolution of phase structure after introducing RE ions was confirmed.A high piezoelectric coefficient d_(33) of ~190 pC/N was achieved due to the improved dielectric constant in the state with stable electric field-induced ferroelectric *** high strain property and converse piezoelectric coefficient d_(33)* of ~340 pm/V were obtained in the state with the coexistence of nonergodic and ergodic relaxor phases when T_(f-r) approached room *** degenerated overall electromechanical properties exhibited in the state with complete ergodic relaxor *** study affords a significant guidance for optimizing the piezoelectricity of BNT-based ceramics utilizing rare earth dopants.

关键词： BNT-Based ceramics Rare earth doping Phase structure Electrical properties

Tailoring depolarization temperature by phase transition causing properties evolution in Bi_(0.5)(Na_(1-x)K_(x))_(0.5)TiO_(3)ceramics

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Journal of Materials Science & Technology 2022年第19期114卷 111-119页

作者： Diyan Yang Jihui Han Jie Yin Haoyue Xue jiagang wu Department of Materials Science Sichuan UniversityChengdu610065China

(Bi_(0.5)Na_(0.5))TiO_(3)-based materials have attracted widespread attention due to large electro-strain,large remnant polarization(P r)and high Curie temperature(T C),but the existence of inherent depolarization temperature(T d)limits the temperature stability and application temperature *** this work,we find that K/Na ratio can regulate T d(from 90℃to 246℃)of the ceramics,which confirms that the increase of K substitution can effectively improve the temperature stability of the *** phase structure and electrical properties of Bi_(0.5)(Na_(1-x)K_(x))_(0.5)TiO_(3)(BNKT x)ceramics can be well modulated by changing K/*** addition,BNKT x system exhibits excellent piezoelectric response at morphotropic phase boundary(MPB)of 20%BKT content(d_(33)=180 pC/N),where rhombohedral(R 3 c)phase and tetragonal(P 4 bm)phase coexist in *** K further substitution,BNKT x ceramics transform into tetragonal phase,and the domain size grows due to the structural transition from short-range-correlated P 4 bm to long-range-correlated P 4 *** deferment of T d is also tightly related to the increase of P 4 mm/P 4 bm *** work can provide an effective way to tailor depolarization temperature and electrical properties of BNT-based ceramics.

关键词： Depolarization temperature (Bi_(0.5)Na_(0.5))Ti_(O 3) Piezoelectric ceramics Piezoelectric constant Temperature stability

Multifunctional barium titanate ceramics via chemical modification tuning phase structure

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InfoMat 2020年第6期2卷 1163-1190页

作者： Chunlin Zhao Yanli Huang jiagang wu Department of Materials Science Sichuan UniversityChengduChina

Global environmental concerns on the toxicity of lead-based piezoelectrics impel the great mass fervor on investigations of lead-free *** titanate(BaTiO3,BT)ceramics,the first discovered perovskite ferroelectrics,were widely employed to fabricate dielectric capacitors from *** a piezoelectric breakthrough was achieved via chemical modification,intensive researches have been performed embracing lead-free BT-based piezoelectrics and their extensional *** this review,we encompass the stateof-the-art progress on chemical modification tuning phase structure toward advanced electrical properties in BT-based ***,modulated regularity of cations substitution on phase transition is summarized and ***,we highlight the common methodologies of phase structure(phase boundary,relaxor phase,room-temperature phase transition,etc.)design for optimizing piezoelectricity,electrostrictive strain,electrocaloric,dielectric energy storage or permittivity performances,and cover the noticeable developments and relevant physical ***,perspectives and challenges on future research issues are *** review proposes to exert the significant guidance and service for material design of BT-based and other lead-free perovskite materials with superior functionalities.

关键词： barium titanate-based ceramics chemical modification design methodologies electrical properties phase structure

Effect of La and Co-doping on microstructure and electrical properties of Bi FeO_3 thin films

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Chinese Science Bulletin 2014年第36期59卷 5205-5211页

作者： jiagang wu Dingquan Xiao Jianguo Zhu Department of Materials Science Sichuan University

Adding both La3+and Co3+was used to tune the microstructure and electrical properties of Bi Fe O3(BFO) thin films, and Bi1-xLaxFe0.90Co0.10O3 thin films were grown on the Sr Ru O3-buffered Pt-coated silicon substrates by a radio frequency sputtering. A polycrystalline structure with(110) orientation was shown in thin films, and their resistivity dramatically increases as the La3+content increases. Their dielectric constant increases,and dielectric loss decreases with increasing La3+*** addition, their ferroelectric and fatigue properties were enhanced with rising La3+content. The thin films with x = 0.03 have optimum electrical properties(e.g., remanent polarization 2Pr* 175.6 l C/cm2, coercive field2Ec* 699.5 k V/mm, dielectric constant er* 257 and tan d * 0.038), together with a good fatigue behavior. The impendence analysis of the films was conducted to identify the defects type during conductivity, and both hopping electrons and single-charged oxygen vacancies are mainly responsible for the conduction of grain and grain boundaries regardless of La3+content. As a result, the doping with both La3+and Co3+benefits the improvement in the electrical properties of BFO thin films.

关键词：电性能薄膜掺杂微结构抗疲劳性能 Co La 介电常数

Coupling effects of the A-site ions on high-performance potassium sodium niobate ceramics

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Journal of Materials Science & Technology 2022年第35期130卷 198-207页

作者： Xiang Lv Nan Zhang Yinchang Ma Xi-xiang Zhang jiagang wu Department of Materials Science Sichuan UniversityChengdu 610065China Division of Physical Science and Engineering King Abdullah University of Science and TechnologyThuwal 23955-6900Saudi Arabia

Although vast efforts have been given to the phase boundary engineering(PBE) of potassium sodium niobate(KNN) ceramics by using chemical dopants,the inherent issues like the K/Na ratio were not paid enough attention,hindering the further understanding of physical ***,we investigated the effect of the K/Na ratio on PBE-featured KNN-based *** K/Na ratio significantly influences the local A-site environment and thereby alters mesoscopic ferroelectric domains and macroscopic structure and performance.A much higher Na^(+)content results in the local stress heterogeneity,while a much higher K^(+)content brings in the local polar *** to the appropriate coupling between the local stress and the polar heterogeneity,piezoelectric properties and the temperature stability of electrostrain are optimized on the Na-rich ***,beyond seeking appropriate chemical dopants,elaborately tailoring the K/Na ratio is also important for further improving the piezoelectric properties of PBE-featured KNN-based ceramics.

关键词： KNN ceramics K/Na ratio Piezoelectricity Local heterogeneity Physical mechanisms

Strain regulation via composition and valence dependent substitution in BNT-based solid solutions

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Advanced Powder Materials

Advanced Powder Materials 2023年第1期2卷 91-99页

作者： Xiaojun wu Chao wu Diyan Yang Jie Yin jiagang wu College of Materials Science and Engineering Sichuan UniversityChengdu 610064China

Simultaneous composition and valence-dependent strain regulation is achieved in lead-free(Bi_(0.5)Na_(0.4)K_(0.1))_(1-2x)Sm_(2x)Ti_(1-x)Mn_(x)O_(3)(BNKT-SM100x)ceramics by a facile co-doping design with Sm^(3+)and Mn^(2+).By simply controlling the sintering temperature,Mn ions exhibited mixed-oxidation states with different ion radius and electronic structures,further adjusting the crystalline *** regulated disorder degree finally induced large electro-strain(0.445%)under appropriate doping contents(x=0.01)and sintering temperature(1150℃).Moreover,the random effect of Mn^(2+)(arising from the different valence and radius comparing with Ti^(4+))is stronger than the pinning effect due to the suppressed oxygen vacancies,and the different crystal structures may also affect the role of Mn^(2+).The domain morphologies with mixed nanodomain and ferroelectric domain were observed in the BNKT-SM1 ceramics,further demonstrating the coexistence of random effect and pinning *** is believed that the self-strain regulation phenomenon in this work may serve as an effective strategy for designing ferroelectrics with high strain performance.

关键词： Lead-free piezoelectric BNKT Strain regulation Mn valence Ferroelectric ceramics