Lead-free(K_(0.5)Na_(0.5))NbO_(3)(KNN)and Li_(0.06)(K_(0.5)Na_(0.5))_(0.94)NbO_(3)(LKNN)thin films were fabricated by a sol-gel method.The effects of Li substitution on crystal structure,microstructure and electrical ...Lead-free(K_(0.5)Na_(0.5))NbO_(3)(KNN)and Li_(0.06)(K_(0.5)Na_(0.5))_(0.94)NbO_(3)(LKNN)thin films were fabricated by a sol-gel method.The effects of Li substitution on crystal structure,microstructure and electrical properties of KNN film were systematically studied.Li doping can enhance the ferroelectric and piezoelectric properties of KNN film.Compared with pure KNN film,the LKNN film possesses larger remanent polarization(P_(r)~9.3μC/cm^(2))and saturated polarization(P_(s)~41.2μC/cm^(2))and lower leakage current density(~10^(−5)A/cm^(2)at 200 kV/cm).Meanwhile,a typical butterfly shaped piezoelectric response curve is obtained in the LKNN film with a high piezoelectric coefficient(d_(33)~105 pm/V).Excellent fatigue resistance(~10^(9)switching cycles)and aging resistance(~180 days)demonstrate the long-term working stability of LKNN film.These findings indicate that KNN-based lead-free piezoelectric films have a broad application prospect in microelectromechanical systems(MEMS).展开更多
Lead-free relaxor ceramics(1−x)K_(0.5)Na_(0.5)NbO_(3)−xBi(Mn_(0.5)Ni_(0.5))O_(3)((1−x)KNN-xBMN)with considerable charge-discharge characteristics and energy storage properties were prepared by a solid state method.Rem...Lead-free relaxor ceramics(1−x)K_(0.5)Na_(0.5)NbO_(3)−xBi(Mn_(0.5)Ni_(0.5))O_(3)((1−x)KNN-xBMN)with considerable charge-discharge characteristics and energy storage properties were prepared by a solid state method.Remarkable,a BMN doping level of 0.04,0.96KNN-0.04BMN ceramic obtained good energy storage performance with acceptable energy storage density Wrec of 1.826 J/cm^(3) and energy storage efficiencyηof 77.4%,as well as good frequency stability(1-500 Hz)and fatigue resistance(1-5000 cycles).Meanwhile,a satisfactory charge-discharge performance with power density PD~98.90 MW/cm^(3),discharge time t0.9<70 ns and temperature stability(30-180°C)was obtained in 0.96KNN-0.04BMN ceramic.The small grain size(~150 nm)and the high polarizability of Bi3+are directly related to its good energy storage capacity.This work proposes a feasible approach for lead-free KNN-based ceramics to achieve high-energy storage and ultra-fast charge-discharge performance as well as candidate materials for the application of advanced high-temperature pulse capacitors.展开更多
Dense(Na_(0.5)K_(0.5))NbO_(3)lead-free ceramics with the simple composition were prepared via sintering in low oxygen partial pressure(pO_(2),~10^(−12) atm)atmosphere and adding LiF.All the ceramics have pure orthorho...Dense(Na_(0.5)K_(0.5))NbO_(3)lead-free ceramics with the simple composition were prepared via sintering in low oxygen partial pressure(pO_(2),~10^(−12) atm)atmosphere and adding LiF.All the ceramics have pure orthorhombic structure.Compared to the LiF-added(Na_(0.5)K_(0.5))NbO_(3)ceramics sintered in air and the low pO_(2)-sintered pure(Na_(0.5)K_(0.5))NbO_(3)ceramics without LiF addition,the present ceramics exhibit improved piezoelectric and ferroelectric properties.The piezoelectric constant d33 is 125 pC/N,and the converse piezoelectric constant d_(33)^(*)is 186 pm/V.The dielectric constant and dielectric loss of the ceramics at room temperature and 1 kHz are 451 and 0.03,respectively.Under the measured electric field of 70 kV/cm,the remanent polarization is 25.9μC/cm^(2)and the coercive field is 13.9 kV/cm.Furthermore,if the base metals such as Cu and Ni powders were mixed into the green pellets and sintered in the low pO_(2)atmosphere,the base metals cannot be oxidized,suggesting possibility of using base metals as electrodes.展开更多
Influence of BiFeO_(3)(BF)on phase formation,unit cell parameters,microstructure,dielectric and ferroelectric properties of solid solutions close to the morphotropic phase boundary in the(Na_(0.5)Bi_(0.5))TiO_(3)–(K_...Influence of BiFeO_(3)(BF)on phase formation,unit cell parameters,microstructure,dielectric and ferroelectric properties of solid solutions close to the morphotropic phase boundary in the(Na_(0.5)Bi_(0.5))TiO_(3)–(K_(0.5)Na_(0.5))NbO_(3) system additionally modified by the low-melting KCl additives has been studied.The formation of pure perovskite structure samples decrease in the unit cell parameters and increase in the TC value stimulated by the BF addition have been revealed.It was proved that modification of compositions by small amounts of the BF and KCl additives leads to improvement of dielectric parameters.展开更多
Lead-free ferroelectric K_(0.5)Na_(0.5)NbO_(3)(KNN)films with different thicknesses were prepared by polyvinlypyrrolidone(PVP)-modified chemical solution deposition(CSD)method.Their residual stresses were studied with...Lead-free ferroelectric K_(0.5)Na_(0.5)NbO_(3)(KNN)films with different thicknesses were prepared by polyvinlypyrrolidone(PVP)-modified chemical solution deposition(CSD)method.Their residual stresses were studied with two methods of X-ray diffraction(XRD)and nanoindentation fracture.It was found that the tensile stress occurs in KNN films with small thickness of 1.3μm after all kinds of stresses were neutralized,which is mainly originated from the interaction across grain boundaries.With increasing the thickness to 2.5μm and above it,the residual stress changed from tensile stresses to compressive stresses,and the compressive stress decreased with the thickness increased.These results could explain why a thicker KNN film can show improved electrical properties and the larger the thickness,the better the ferroelectric and piezoelectric properties.展开更多
teviseuzobeptehberzoriLead-free(K_(0.5)Na_(0.5))NbO_(3)(KNN)nanopowder with perovskite structure was synthesized bymechanochemical synthesis method successfully.In order to investigate the perovskite phaseformation of...teviseuzobeptehberzoriLead-free(K_(0.5)Na_(0.5))NbO_(3)(KNN)nanopowder with perovskite structure was synthesized bymechanochemical synthesis method successfully.In order to investigate the perovskite phaseformation of KNN powders during the mechanochemical synthesis process,we set up three millingroutes with different transmission ratios(W_(v)/W_(p))acting on the mixed starting powders of Na_(2)CO_(3),K_(2)CO_(3)and Nb_(2)O_(5).KNN perovskite phase was not detected by XRD under the lowtransmission ratios-2 with the shock power of 273 W.When the transmission ratios wasincreased to-2.75 with the shock power of 683.4 W,KNN perovskite phase was formed aftermilling for 22 h.Based on these results it has been found,that in shock mode process(SMIP),thathigher shock power is helpful for the formation KNN perovskite phase.The critical shock powerPaitial and critical weight-normalized cumulative shock energy P^(*)_(critical)in KNN system are dis-cussed.Compared with SMP,when W_(v)/W_(p),=-3.5,in friction mode process(FMiP),KNN per-ovskite phase was formed after milling for 5 h.It implis that FMP benefit the formation of KNNperovslkite phase,The morphology of KNN powder was observed by transmsion electronmicroscopy(TEM).展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.51972144 and U1806221)the Taishan Scholars Program,the Case-by-Case Project for Top Outstanding Talents of Jinan,the Shandong Provincial Natural Science Foundation(Grant No.ZR2020KA003)+2 种基金the Primary Research&Development Plan of Shandong Province(Grant No.2019JZZY010313)the Project of“20 Items of University”of Jinan(Grant Nos.T202009 and T201907)the Introduction Program of Senior Foreign Experts(G2021024003L).
文摘Lead-free(K_(0.5)Na_(0.5))NbO_(3)(KNN)and Li_(0.06)(K_(0.5)Na_(0.5))_(0.94)NbO_(3)(LKNN)thin films were fabricated by a sol-gel method.The effects of Li substitution on crystal structure,microstructure and electrical properties of KNN film were systematically studied.Li doping can enhance the ferroelectric and piezoelectric properties of KNN film.Compared with pure KNN film,the LKNN film possesses larger remanent polarization(P_(r)~9.3μC/cm^(2))and saturated polarization(P_(s)~41.2μC/cm^(2))and lower leakage current density(~10^(−5)A/cm^(2)at 200 kV/cm).Meanwhile,a typical butterfly shaped piezoelectric response curve is obtained in the LKNN film with a high piezoelectric coefficient(d_(33)~105 pm/V).Excellent fatigue resistance(~10^(9)switching cycles)and aging resistance(~180 days)demonstrate the long-term working stability of LKNN film.These findings indicate that KNN-based lead-free piezoelectric films have a broad application prospect in microelectromechanical systems(MEMS).
基金supported by the National Natural Science Foundation of China(NSFC)(Grant No.52272119,51872177)the Natural Science Basic Research Plan in the Shaanxi Province of China(Grant No.2021ZDLSF06-03,2021JM-201)+1 种基金the Fundamental Research Funds for the Central Universities(Program No.GK202002014)the Fondamental Innovation Project in School of Materials Science and Engineering(SNNU).
文摘Lead-free relaxor ceramics(1−x)K_(0.5)Na_(0.5)NbO_(3)−xBi(Mn_(0.5)Ni_(0.5))O_(3)((1−x)KNN-xBMN)with considerable charge-discharge characteristics and energy storage properties were prepared by a solid state method.Remarkable,a BMN doping level of 0.04,0.96KNN-0.04BMN ceramic obtained good energy storage performance with acceptable energy storage density Wrec of 1.826 J/cm^(3) and energy storage efficiencyηof 77.4%,as well as good frequency stability(1-500 Hz)and fatigue resistance(1-5000 cycles).Meanwhile,a satisfactory charge-discharge performance with power density PD~98.90 MW/cm^(3),discharge time t0.9<70 ns and temperature stability(30-180°C)was obtained in 0.96KNN-0.04BMN ceramic.The small grain size(~150 nm)and the high polarizability of Bi3+are directly related to its good energy storage capacity.This work proposes a feasible approach for lead-free KNN-based ceramics to achieve high-energy storage and ultra-fast charge-discharge performance as well as candidate materials for the application of advanced high-temperature pulse capacitors.
基金This work was supported by National Natural Science Foundation of China(No.51972202)Fundamental Research Funds for the Central Universities(No.GK201901005,2019CSLY006).
文摘Dense(Na_(0.5)K_(0.5))NbO_(3)lead-free ceramics with the simple composition were prepared via sintering in low oxygen partial pressure(pO_(2),~10^(−12) atm)atmosphere and adding LiF.All the ceramics have pure orthorhombic structure.Compared to the LiF-added(Na_(0.5)K_(0.5))NbO_(3)ceramics sintered in air and the low pO_(2)-sintered pure(Na_(0.5)K_(0.5))NbO_(3)ceramics without LiF addition,the present ceramics exhibit improved piezoelectric and ferroelectric properties.The piezoelectric constant d33 is 125 pC/N,and the converse piezoelectric constant d_(33)^(*)is 186 pm/V.The dielectric constant and dielectric loss of the ceramics at room temperature and 1 kHz are 451 and 0.03,respectively.Under the measured electric field of 70 kV/cm,the remanent polarization is 25.9μC/cm^(2)and the coercive field is 13.9 kV/cm.Furthermore,if the base metals such as Cu and Ni powders were mixed into the green pellets and sintered in the low pO_(2)atmosphere,the base metals cannot be oxidized,suggesting possibility of using base metals as electrodes.
基金The work was supported by the Russian Foundation for Basic Research(Grant 15-03-03269).
文摘Influence of BiFeO_(3)(BF)on phase formation,unit cell parameters,microstructure,dielectric and ferroelectric properties of solid solutions close to the morphotropic phase boundary in the(Na_(0.5)Bi_(0.5))TiO_(3)–(K_(0.5)Na_(0.5))NbO_(3) system additionally modified by the low-melting KCl additives has been studied.The formation of pure perovskite structure samples decrease in the unit cell parameters and increase in the TC value stimulated by the BF addition have been revealed.It was proved that modification of compositions by small amounts of the BF and KCl additives leads to improvement of dielectric parameters.
基金the support from the Natural Science Foundation of China(Grant No.90923001)the International Science and Technology Cooperation Program of China(Grant Nos.2010DFB13640 and 2011DFA51880)+2 种基金the Shaanxi Province International Collaboration Program(Grant Nos.2009KW-12 and 2010KW-09)the Fundamental Research Funds for the Central Universities(Grant No.0105-08143078)supported by the research grant,SERC of A*STAR(Agency for Science,Technology and Research),Singapore(No.0921150112)。
文摘Lead-free ferroelectric K_(0.5)Na_(0.5)NbO_(3)(KNN)films with different thicknesses were prepared by polyvinlypyrrolidone(PVP)-modified chemical solution deposition(CSD)method.Their residual stresses were studied with two methods of X-ray diffraction(XRD)and nanoindentation fracture.It was found that the tensile stress occurs in KNN films with small thickness of 1.3μm after all kinds of stresses were neutralized,which is mainly originated from the interaction across grain boundaries.With increasing the thickness to 2.5μm and above it,the residual stress changed from tensile stresses to compressive stresses,and the compressive stress decreased with the thickness increased.These results could explain why a thicker KNN film can show improved electrical properties and the larger the thickness,the better the ferroelectric and piezoelectric properties.
基金supported by the National Natural Science Foundation of China No.50872106the National Basic Research Program of China(973 Program)No.2009CB623306.
文摘teviseuzobeptehberzoriLead-free(K_(0.5)Na_(0.5))NbO_(3)(KNN)nanopowder with perovskite structure was synthesized bymechanochemical synthesis method successfully.In order to investigate the perovskite phaseformation of KNN powders during the mechanochemical synthesis process,we set up three millingroutes with different transmission ratios(W_(v)/W_(p))acting on the mixed starting powders of Na_(2)CO_(3),K_(2)CO_(3)and Nb_(2)O_(5).KNN perovskite phase was not detected by XRD under the lowtransmission ratios-2 with the shock power of 273 W.When the transmission ratios wasincreased to-2.75 with the shock power of 683.4 W,KNN perovskite phase was formed aftermilling for 22 h.Based on these results it has been found,that in shock mode process(SMIP),thathigher shock power is helpful for the formation KNN perovskite phase.The critical shock powerPaitial and critical weight-normalized cumulative shock energy P^(*)_(critical)in KNN system are dis-cussed.Compared with SMP,when W_(v)/W_(p),=-3.5,in friction mode process(FMiP),KNN per-ovskite phase was formed after milling for 5 h.It implis that FMP benefit the formation of KNNperovslkite phase,The morphology of KNN powder was observed by transmsion electronmicroscopy(TEM).
