The dielectric response of complex perovskite relaxor ferrolectrics Pb(Mg1/3Nb2/3) O3 with respect to temperature and frequency was carefully measured. Using a normalized method of the 'universal' many-body t...The dielectric response of complex perovskite relaxor ferrolectrics Pb(Mg1/3Nb2/3) O3 with respect to temperature and frequency was carefully measured. Using a normalized method of the 'universal' many-body theory, the relaxation process was analyzed around the temperature of dielectric absorption maximum. There is no structural phase transition near this temperature and the behavior is closely like that of a polar dipole medium. The functional relationship about frequency and temperature of dielectric pormittivity maximum was also fitted to discuss the dynamic behavior of polar microregion. It is confirmed that a new power exponential Arrhenius relation is better to characterize the relaxation behavior than the Vogel-Fulcher and Debye relations. Based on the polarization theory of polar dipoles, we analyzed the relaxation mechanism of ferroelectric microdomains of relaxor ferroelectrics, and get an ideal distribution function of relaxation time. Consequently, a simulated dielectric response dependence on temperature and frequencies can be expressed, which is well coincided with experiment results.展开更多
RELAXOR ferroelectric ceramics with complex perovskite structure is considered as the first material chosen for multilayer capacitors (MLC) in technology and economy, because of their high permittivity, lower sinterin...RELAXOR ferroelectric ceramics with complex perovskite structure is considered as the first material chosen for multilayer capacitors (MLC) in technology and economy, because of their high permittivity, lower sintering temperature and lower capacitors changing rate with temperature (temperature coefficient) for diffuse phase transition (DPT). Thus, preparations and properties about the materials received more attention. There are many reports about their dielectric properties but there are few about their poled dielectric behavior. In the展开更多
Substitutional charge disorder as in PbMg_(1/3)Nb_(2/3)O_(3),structural cation vacancies as in Sr_(x)Ba_(1-x)Nb_(2)O_(6) and isovalent substitution of off-centered cations as in BaTi_(1-x)Sn^(x)O_(3) and BaTi1-xZrxO_(...Substitutional charge disorder as in PbMg_(1/3)Nb_(2/3)O_(3),structural cation vacancies as in Sr_(x)Ba_(1-x)Nb_(2)O_(6) and isovalent substitution of off-centered cations as in BaTi_(1-x)Sn^(x)O_(3) and BaTi1-xZrxO_(3) give rise to quenched electric random-fields(RFs),which we proposed to be at the origin of the peculiar behavior of relaxor ferroelectrics 20 years ago.These are,e.g.a strong frequency dispersion of the dielectric response and an apparent lack of macroscopic symmetry breaking in the low temperature phase.Both are related to mesoscopic RF-driven phase transitions,which give rise to irregularly shaped quasi-stable polar nanoregions below the characteristic temperature T^(*),but above the global transition temperature Tc.Their co-existence with the paraelectric parent phase can be modeled by time-dependentfield equations under the control of quenched RFs and stress-free strain(in the case of order parameter dimension n2).Transitions into global polar order at Tc may occur in uniaxial relaxors as observed on the uniaxial relaxor ferroelectric Sr0.8Ba_(0.2)Nb_(2)O_(6) and come close to RF Ising model criticality.Re-entrant relaxor transitions as observed in solid solutions of Ba_(2)Pr_(0.6)Nd_(0.4)(FeNb_(4))O_(15) are proposed to evidence the coexistence of distinct normal and relaxor ferroelectric phases within the framework of percolation theory.Keywords.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
文摘The dielectric response of complex perovskite relaxor ferrolectrics Pb(Mg1/3Nb2/3) O3 with respect to temperature and frequency was carefully measured. Using a normalized method of the 'universal' many-body theory, the relaxation process was analyzed around the temperature of dielectric absorption maximum. There is no structural phase transition near this temperature and the behavior is closely like that of a polar dipole medium. The functional relationship about frequency and temperature of dielectric pormittivity maximum was also fitted to discuss the dynamic behavior of polar microregion. It is confirmed that a new power exponential Arrhenius relation is better to characterize the relaxation behavior than the Vogel-Fulcher and Debye relations. Based on the polarization theory of polar dipoles, we analyzed the relaxation mechanism of ferroelectric microdomains of relaxor ferroelectrics, and get an ideal distribution function of relaxation time. Consequently, a simulated dielectric response dependence on temperature and frequencies can be expressed, which is well coincided with experiment results.
文摘RELAXOR ferroelectric ceramics with complex perovskite structure is considered as the first material chosen for multilayer capacitors (MLC) in technology and economy, because of their high permittivity, lower sintering temperature and lower capacitors changing rate with temperature (temperature coefficient) for diffuse phase transition (DPT). Thus, preparations and properties about the materials received more attention. There are many reports about their dielectric properties but there are few about their poled dielectric behavior. In the
文摘Substitutional charge disorder as in PbMg_(1/3)Nb_(2/3)O_(3),structural cation vacancies as in Sr_(x)Ba_(1-x)Nb_(2)O_(6) and isovalent substitution of off-centered cations as in BaTi_(1-x)Sn^(x)O_(3) and BaTi1-xZrxO_(3) give rise to quenched electric random-fields(RFs),which we proposed to be at the origin of the peculiar behavior of relaxor ferroelectrics 20 years ago.These are,e.g.a strong frequency dispersion of the dielectric response and an apparent lack of macroscopic symmetry breaking in the low temperature phase.Both are related to mesoscopic RF-driven phase transitions,which give rise to irregularly shaped quasi-stable polar nanoregions below the characteristic temperature T^(*),but above the global transition temperature Tc.Their co-existence with the paraelectric parent phase can be modeled by time-dependentfield equations under the control of quenched RFs and stress-free strain(in the case of order parameter dimension n2).Transitions into global polar order at Tc may occur in uniaxial relaxors as observed on the uniaxial relaxor ferroelectric Sr0.8Ba_(0.2)Nb_(2)O_(6) and come close to RF Ising model criticality.Re-entrant relaxor transitions as observed in solid solutions of Ba_(2)Pr_(0.6)Nd_(0.4)(FeNb_(4))O_(15) are proposed to evidence the coexistence of distinct normal and relaxor ferroelectric phases within the framework of percolation theory.Keywords.
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.
