The giant dielectric bchavior of CaCu_(3)Ti_(4)0_(12)(CCTO)has been widely investigated owing to its potential applications in electronics;however,the loss tangent(tan8)of this material is too large for many applicati...The giant dielectric bchavior of CaCu_(3)Ti_(4)0_(12)(CCTO)has been widely investigated owing to its potential applications in electronics;however,the loss tangent(tan8)of this material is too large for many applications.A partial substitution of CCTO ceramics with either Al^(3+) or Ta^(5+)-ions generally results in poorer nonlinear properties and an associated increase in tan8(to~0.29-1.15).However,first-principles calculations showed that self-charge compensation occurs between these two dopant ions when co-doped into Tit sites,which can improve the electrical properties of the grain boundary(GB).Surprisingly,in this study,a greatly enhanced breakdown electric field(~200--6588 V/cm)and nonlinear coefficient(-4.8-15.2)with a significantly reduced tan8(~0.010--0.036)were obtained by simultaneous partial substitution of CCTO with acceptor-donor(Al^(3+),Ta^(5+))dopants to produce(Al^(3+),Ta^(5+))-CCTO ceramics.The reduced tan8 and improved nonlinear properties were attributed to the synergistic effects of the co-dopants in the doped CCTO structure.The signifcant reduction in the mean grain size of the(Al^(3+),Ta^(5+))-CCTO ceramics compared to pure CCTO was mainly because of the Ta^(5+)-ions.Accordingly,the increased GB density due to the reduced grain size and the larger Schottky barrier height(Ф_(b))at the GBs of the co-doped CCTO ceramics were the main reasons for the greatly increased GB resistance,improved nonlinear properties,and reduced tan8 values compared to pure and single-doped CCTO.In addition,high dielectric constant values(ε'≈(0.52-2.7)×10^(4))were obtained.A fine-grained microstructure with highly insulating GBs was obtained by Ta doping,while co-doping with Ta^(5+) and Al^(3+ )resulted in a high Ф_(b).The obtained results are expected to provide useful guidelines for developing new giant dielectric ceramics with excellent dielectric properties.展开更多
基金supported by the Basic Research Fund of Khon Kaen University.It was partially supported by the Research Network NANOTEC(RNN)program of the National Nanotechnology Center(NANOTEC),NSTDA,Ministry of Higher Education,Science,Research,and Innovation(MHESI,Thailand)(Grant No.PI851882)Khon Kaen University,Thailand.J.Boonlakhom would like to thank the Graduate School of Khon Kaen University(Grant No.581T211)for his Ph.D.scholarship.
文摘The giant dielectric bchavior of CaCu_(3)Ti_(4)0_(12)(CCTO)has been widely investigated owing to its potential applications in electronics;however,the loss tangent(tan8)of this material is too large for many applications.A partial substitution of CCTO ceramics with either Al^(3+) or Ta^(5+)-ions generally results in poorer nonlinear properties and an associated increase in tan8(to~0.29-1.15).However,first-principles calculations showed that self-charge compensation occurs between these two dopant ions when co-doped into Tit sites,which can improve the electrical properties of the grain boundary(GB).Surprisingly,in this study,a greatly enhanced breakdown electric field(~200--6588 V/cm)and nonlinear coefficient(-4.8-15.2)with a significantly reduced tan8(~0.010--0.036)were obtained by simultaneous partial substitution of CCTO with acceptor-donor(Al^(3+),Ta^(5+))dopants to produce(Al^(3+),Ta^(5+))-CCTO ceramics.The reduced tan8 and improved nonlinear properties were attributed to the synergistic effects of the co-dopants in the doped CCTO structure.The signifcant reduction in the mean grain size of the(Al^(3+),Ta^(5+))-CCTO ceramics compared to pure CCTO was mainly because of the Ta^(5+)-ions.Accordingly,the increased GB density due to the reduced grain size and the larger Schottky barrier height(Ф_(b))at the GBs of the co-doped CCTO ceramics were the main reasons for the greatly increased GB resistance,improved nonlinear properties,and reduced tan8 values compared to pure and single-doped CCTO.In addition,high dielectric constant values(ε'≈(0.52-2.7)×10^(4))were obtained.A fine-grained microstructure with highly insulating GBs was obtained by Ta doping,while co-doping with Ta^(5+) and Al^(3+ )resulted in a high Ф_(b).The obtained results are expected to provide useful guidelines for developing new giant dielectric ceramics with excellent dielectric properties.
