(Pb_(0.8)Ba_(0.2))[(Zn_(1/3)Nb_(2/3))_(0.7)Ti_(0.3)]O_(3)relaxor-type ferroelectric ceramics was obtained via classical solid-state reaction.The hysteresis loop results were discussed in the frame of ergodicity criter...(Pb_(0.8)Ba_(0.2))[(Zn_(1/3)Nb_(2/3))_(0.7)Ti_(0.3)]O_(3)relaxor-type ferroelectric ceramics was obtained via classical solid-state reaction.The hysteresis loop results were discussed in the frame of ergodicity criterium around the characteristic ferroelectric relaxor freezing temperature.Slimer hysteresis loops were observed below the freezing temperature reflecting an ergodic relaxor behavior.Above this temperature,estimated around 223K for the studied system,larger and unsaturated like ferroelectric hysteresis loops were observed.This temperature also coincides with the slope change on maximum polarization and inflection point of remnant polarization curves.Energy storage,energy loss and efficiency values were determined in a wide temperature range.While the recoverable energy density shows relatively low values(0.23 J/cm^(3)),there are interesting behaviors for this parameter and for the efficiency,since the two physical quantities increase versus temperature and the efficiency even reaches the value of 97%.展开更多
The relaxor behavior of PLZT ferroelectric ceramics has been analyzed in a wide frequency and temperature ranges,below and above the temperature for the formation of the so-called polar nano-regions(PNRs).An approxima...The relaxor behavior of PLZT ferroelectric ceramics has been analyzed in a wide frequency and temperature ranges,below and above the temperature for the formation of the so-called polar nano-regions(PNRs).An approximation to the dynamical behavior of the PNRs has been discussed using Cole-Cole’s relaxation model and Jonscher’s Universal Relaxation Law.The analysis considers both the dipolar contribution and those ones associated with DC and AC electric conductivities,this latter not being previously reported in the literature for relaxor materials.The effectiveness of the developed model has been verified from the agreement between the experimental data and the theoretical calculations.This study also offers an indirect method to predict the DC component of the electrical conductivity.展开更多
Conventional solid state reaction method,from oxides and carbonates,was employed to prepare bismuth(Bi)-based multiferroic systems.The undoped BiFeO_(3)(BFO)and the codoped system with Ba,La and Ti(Bi_(1-x)Ba_(x)Fe_(1...Conventional solid state reaction method,from oxides and carbonates,was employed to prepare bismuth(Bi)-based multiferroic systems.The undoped BiFeO_(3)(BFO)and the codoped system with Ba,La and Ti(Bi_(1-x)Ba_(x)Fe_(1-y)Ti_(y)O_(3),Bi_(1-x-z)Ba_(x)LazFe_(1-y)TiyO_(3))with x,y,z=0.1 were prepared stoichiometrically and sintered at two different temperatures.The structural and magnetic properties were investigated at room temperature.XRD measurements confirm the obtaining of the rhombohedral perovskite structure of the BFO family system.For the undoped system,some reflections of undesired phases are present for two different sintering temperatures,while for the doped system only one phase is present for both temperatures.The magnetic characterization at room temperature revealed remarkable differences between the ceramic samples.The results show that for undoped BFO system,spontaneous magnetization is not observed at room temperature.Nevertheless,in doped one,a well-defined ferromagnetic behavior is observed at room temperature,possible,due to the suppression of the spatially modulated spin structure of BFO promoted by the reduction of the rhombohedral distortion and the weakening of the Bi-O bonds.The XPS results confirm the presence of oxygen vacancies and the coexistence of Fe^(3+)and Fe^(2+) in all the studied samples.Calorimetric measurements reveal that the dopant incorporation has not a direct effect in Neel temperature but possibly yes in ferroelectric-paraelectric transition.展开更多
The impedance properties in polarized piezoelectric can be described by electric equivalent circuits.The classic circuit used in the literature to describe real systems is formed by one resistor(R),one inductance(L)an...The impedance properties in polarized piezoelectric can be described by electric equivalent circuits.The classic circuit used in the literature to describe real systems is formed by one resistor(R),one inductance(L)and one capacitance C connected in series and one capacity(C_(0))connected in parallel with the formers.Nevertheless,the equation that describe the resonance and anti-resonance frequencies depends on a complex manner of R,L,C and C_(0).In this work is proposed a simpler model formed by one inductance(L)and one capacity(C)in series;one capacity(C_(0))in parallel;one resistor(R_(p))in parallel and one resistor(Rs)in series with other components.Unlike the traditional circuit,the equivalent circuit elements in the proposed model can be simply determined by knowing the experimental values of the resonance frequency fr,anti-resonance frequency fa,impedance module at resonance frequency|Z|,impedance module at anti-resonance frequency|Za|and low frequency capacitance C_(0),without ftting the im-pedance experimental data to the obtained equation.展开更多
基金the Third World Academy of Sciences(RG/PHYS/LA No.99-050,02-225 and 05-043)support and ICTP for financial support of Latin-American Network of Ferroelectric Materials(NT-02)+1 种基金the National Program for Nanoscience and Nanotechnology of Cuba(Project No.PN211LH008-035)the National Program for Basic Sciences of Cuba(Project No.PN223LH010-023).
文摘(Pb_(0.8)Ba_(0.2))[(Zn_(1/3)Nb_(2/3))_(0.7)Ti_(0.3)]O_(3)relaxor-type ferroelectric ceramics was obtained via classical solid-state reaction.The hysteresis loop results were discussed in the frame of ergodicity criterium around the characteristic ferroelectric relaxor freezing temperature.Slimer hysteresis loops were observed below the freezing temperature reflecting an ergodic relaxor behavior.Above this temperature,estimated around 223K for the studied system,larger and unsaturated like ferroelectric hysteresis loops were observed.This temperature also coincides with the slope change on maximum polarization and inflection point of remnant polarization curves.Energy storage,energy loss and efficiency values were determined in a wide temperature range.While the recoverable energy density shows relatively low values(0.23 J/cm^(3)),there are interesting behaviors for this parameter and for the efficiency,since the two physical quantities increase versus temperature and the efficiency even reaches the value of 97%.
基金The authors would like to acknowledge the Third World Academy of Sciences(RG/PHYS/LA Nos.99-050,02-225,and 05-043),the Abdus Salam International Centre for Theoretical Physics(ICTP),Trieste,Italy,for financially supporting the Latin-American Network of Ferroelectric Materials(NT-02)and the National Council of Scientific and Technological Development(CNPq)grant 303447/2019-2Minas Gerais Research Foundation(FAPEMIG)grants PPM-00661-16 and APQ-02875-18Coordenacao de Aperfeicoamento de Pessoal de Nível Superior-Brasil(CAPES)-Finance Code 001,and Sao Paulo Research Foundation(FAPESP)grants 06/60013-5 and 2018/24352-7 Brazilian agencies for the financial support.
文摘The relaxor behavior of PLZT ferroelectric ceramics has been analyzed in a wide frequency and temperature ranges,below and above the temperature for the formation of the so-called polar nano-regions(PNRs).An approximation to the dynamical behavior of the PNRs has been discussed using Cole-Cole’s relaxation model and Jonscher’s Universal Relaxation Law.The analysis considers both the dipolar contribution and those ones associated with DC and AC electric conductivities,this latter not being previously reported in the literature for relaxor materials.The effectiveness of the developed model has been verified from the agreement between the experimental data and the theoretical calculations.This study also offers an indirect method to predict the DC component of the electrical conductivity.
文摘Conventional solid state reaction method,from oxides and carbonates,was employed to prepare bismuth(Bi)-based multiferroic systems.The undoped BiFeO_(3)(BFO)and the codoped system with Ba,La and Ti(Bi_(1-x)Ba_(x)Fe_(1-y)Ti_(y)O_(3),Bi_(1-x-z)Ba_(x)LazFe_(1-y)TiyO_(3))with x,y,z=0.1 were prepared stoichiometrically and sintered at two different temperatures.The structural and magnetic properties were investigated at room temperature.XRD measurements confirm the obtaining of the rhombohedral perovskite structure of the BFO family system.For the undoped system,some reflections of undesired phases are present for two different sintering temperatures,while for the doped system only one phase is present for both temperatures.The magnetic characterization at room temperature revealed remarkable differences between the ceramic samples.The results show that for undoped BFO system,spontaneous magnetization is not observed at room temperature.Nevertheless,in doped one,a well-defined ferromagnetic behavior is observed at room temperature,possible,due to the suppression of the spatially modulated spin structure of BFO promoted by the reduction of the rhombohedral distortion and the weakening of the Bi-O bonds.The XPS results confirm the presence of oxygen vacancies and the coexistence of Fe^(3+)and Fe^(2+) in all the studied samples.Calorimetric measurements reveal that the dopant incorporation has not a direct effect in Neel temperature but possibly yes in ferroelectric-paraelectric transition.
文摘The impedance properties in polarized piezoelectric can be described by electric equivalent circuits.The classic circuit used in the literature to describe real systems is formed by one resistor(R),one inductance(L)and one capacitance C connected in series and one capacity(C_(0))connected in parallel with the formers.Nevertheless,the equation that describe the resonance and anti-resonance frequencies depends on a complex manner of R,L,C and C_(0).In this work is proposed a simpler model formed by one inductance(L)and one capacity(C)in series;one capacity(C_(0))in parallel;one resistor(R_(p))in parallel and one resistor(Rs)in series with other components.Unlike the traditional circuit,the equivalent circuit elements in the proposed model can be simply determined by knowing the experimental values of the resonance frequency fr,anti-resonance frequency fa,impedance module at resonance frequency|Z|,impedance module at anti-resonance frequency|Za|and low frequency capacitance C_(0),without ftting the im-pedance experimental data to the obtained equation.