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

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 property.Compared to other chemical modifications,rare earth ions doping provides sig-nificant possibility to optimize the strain property of BNT-based ceramics.In this work,the effects of rare earth ions on phase structure,microstructure,and strain&electrostrictive properties of lead-free BNT-based ceramics were systematically investigated.Rare earth ions(i.e.,La^(3+),Sm^(3+),Yb^(3+),Dy^(3+),and Nd ^(3+))were selected as the doping ions.Introducing moderate La^(3+)ions can drive the ferroelectric state of BNT-based ceramics to nonergodic relaxor state or ergodic relaxor state.The 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 state.Besides,the giant electrostrictive coefficient Q 33 of~0.047 m 4/C 2 can be obtained for La ^(3+)-doped ceramic with ergodic relaxor state.Other rare earth ions also present the promotion effect on strain enhancement for BNT-based ceramics.This study affords a significant guidance to optimize strain and electrostrictive properties of BNT-based ce-ramics via rare earth ions doping.

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

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 studied.Rare 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) ceramics.It 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 observed.Hereby,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 phase.The 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 temperature.The degenerated overall electromechanical properties exhibited in the state with complete ergodic relaxor phase.This study affords a significant guidance for optimizing the piezoelectricity of BNT-based ceramics utilizing rare earth dopants.

Large electro-strain signal of the BNT-BT-KNN lead-free piezoelectric ceramics with CuO doping

This paper investigates a system of 0.93Bi_(0.5)Na_(0.5)TiO_(3)–0.06BaTiO_(3)–0.01K_(0.5)Na_(0.5)NbO_(3)–xCuO(BNT–BT–KNN–xCuO,x=0-0:04 mol.%)ceramics,which were fabricated by the conventional solid-state process through the granulation of vacuum freeze drier.The results show that the CuO doping made a significant enhancement on the piezoelectric properties of the BNT–BT–KNN ceramics.With the doping of CuO,the transition temperature between ferroelectric phase and ergodic relaxor state is reduced to near room temperature,resulting in pinched P–E loops and“sprout”shape S-E curves.For the composition with x=0.01,a high unipolar strain of 0.39%under 5 kV/mm contributes a large d^(*)33~780 pm/V at room temperature,which is competitive with the other BNT-based ceramics.

Large electric field-induced strain in the novel BNKTAN-BNBLTZ lead-free ceramics

(1-x)Bi0.5(Na0.82K0.18)0.5Ti0.96(Al0.5Nb0.5)0.04O3-xBi0.46Na0.46Ba0.5La0.02Ti0.97Zr0.03O3 lead-free ceramics(abbreviated as BNKTAN-100x BNBLTZ)was prepared by the conventional solid reaction.XRD patterns and EDS spectrums revealed that a stable solid solution had been formed between BNBLTZ and BNKTAN.With the introduction of BNBLTZ anti-ferroelectric content,BNKTAN relaxor ferroelectrics exhibited the excellent field-induced-strain for x=0.04 corresponding to electric field-induced strain S^0.505%and normal strain d33*~777 pm/V at 65 kV/cm.The large strain response was attributed to the emergence of PNRs in the relaxation process.Additionally,an excellent fatigue resistance performance was obtained within 105cycles(S=0.505%–0.495%and d33*=777–758 pm/V,65 kV/cm).It suggested that prepared ceramics had the great potential to strain sensor and actuators.

Electric field-induced photoluminescence quenching in Pr-doped BNT ceramics across the MPB region

Piezophotonics is a great interesting field of physics that has led to a number of important technologies,such as light source,smart sensors,and mechatronics.In this work,we reported Pr-doped(Bi_(0.5)Na_(0.5))TiO_(3)-based lead-free ceramics with strong red photoluminescence emission and large strain response(d_(33)^(*)=460 pm/V,S=0.32%).The PL emission can be quenched by decreasing the intensity by 93%after electrical polarization(E=50 kV/cm).The local structure and electric field-induced structural changes were systematically investigated to reveal the significant distinction in photoluminescence properties caused by electrical polarization.The results indicated that polarization treatment eliminates the structural inhomogeneities and establishes a long-range ferroelectric tetragonal and rhombohedral distortion.The crystal structure transformed irreversibly from a non-ergodic to a normal ferroelectric state.PL quenching originated from the decreased distortion of octahedral due to the transition from a non-ergodic state to a highly ordered symmetrical structure.Meanwhile,the enlarged domain structure contributed to the photoluminescence quenching effect.Our findings demonstrate that an electric field can be a robust tool for adjusting the photoluminescence property and provide insights into the rela-tionship between the structure and PL properties of BNT-based ceramics under an external stimulus.