The Sb2O3-doped TiO2 varistors were obtained by conventional ceramic processing. The 0.75mol%Sb2O3 99.25 mol%TiO2 varistor has a nonlinear coefficient α = 7 and a minimum breakdown electrical field of 6 V/mm. The non...The Sb2O3-doped TiO2 varistors were obtained by conventional ceramic processing. The 0.75mol%Sb2O3 99.25 mol%TiO2 varistor has a nonlinear coefficient α = 7 and a minimum breakdown electrical field of 6 V/mm. The nonlinear electrical behaviour of TiO2.Sb2O3 ceramics was explained by the introduction of defects in the crystal lattice that are responsible for the formation of Schottky potential barriers at grain boundaries.展开更多
An electronic structure of ferroelectric PbZr_(1/2)Ti_(1/2)O_(3) is presented.The full potential linearized augmented plane wave method is used and the exchange correlation effects are treated by the generalized gradi...An electronic structure of ferroelectric PbZr_(1/2)Ti_(1/2)O_(3) is presented.The full potential linearized augmented plane wave method is used and the exchange correlation effects are treated by the generalized gradient approximation.In order to understand the ferroelectricity of PbZr_(1/2)Ti_(1/2)O_(3),the density of states,charge density distribution and band structure are calculated.The results show that the atoms Pb and Ti act similarly as in pure PbTiO_(3).Like other perovskite ABO_(3) ferroelectrics,there is a hybridization between the Ti d and O p states,which is responsible for the tendency to ferroelectricity.展开更多
Based on the results of total-energy calculations for embedded clusters using self-consistent-field Xα-scatteredwave method,we determined the tetragonal fine structure of K(Ta_(0.56)Nb_(0.44))O_(3),i.e.,the equilibri...Based on the results of total-energy calculations for embedded clusters using self-consistent-field Xα-scatteredwave method,we determined the tetragonal fine structure of K(Ta_(0.56)Nb_(0.44))O_(3),i.e.,the equilibrium configuration of B-site cations(Ta and Nb)in the ferroelectric phase.Ta is found to have an off-center displacement of about 0.02A along[001].The off-center displacement of Nb is much larger than that of Ta,thus it makes a major contribution to the occurrence of the ferroelectric instability.展开更多
A simple double-well potential model is established.It shows that the nature of the low-frequency dielectric constant in ferroelectrics is the additional hopping of the off-center ions in multi-site potential.The co-o...A simple double-well potential model is established.It shows that the nature of the low-frequency dielectric constant in ferroelectrics is the additional hopping of the off-center ions in multi-site potential.The co-operative effect causes the fact that the Curie-Weiss law is obeyed.The mechanism of the molecular field is clarified.展开更多
基金Supported by the Basis Science Talent Training Foundation of China,。
文摘The Sb2O3-doped TiO2 varistors were obtained by conventional ceramic processing. The 0.75mol%Sb2O3 99.25 mol%TiO2 varistor has a nonlinear coefficient α = 7 and a minimum breakdown electrical field of 6 V/mm. The nonlinear electrical behaviour of TiO2.Sb2O3 ceramics was explained by the introduction of defects in the crystal lattice that are responsible for the formation of Schottky potential barriers at grain boundaries.
基金Supported by a grant from the State Key Program for Basic Research of China,No.G1998061408.
文摘An electronic structure of ferroelectric PbZr_(1/2)Ti_(1/2)O_(3) is presented.The full potential linearized augmented plane wave method is used and the exchange correlation effects are treated by the generalized gradient approximation.In order to understand the ferroelectricity of PbZr_(1/2)Ti_(1/2)O_(3),the density of states,charge density distribution and band structure are calculated.The results show that the atoms Pb and Ti act similarly as in pure PbTiO_(3).Like other perovskite ABO_(3) ferroelectrics,there is a hybridization between the Ti d and O p states,which is responsible for the tendency to ferroelectricity.
基金Supported by the Doctoral Fund of the State Education Commission of China under Grant No.98042211.
文摘Based on the results of total-energy calculations for embedded clusters using self-consistent-field Xα-scatteredwave method,we determined the tetragonal fine structure of K(Ta_(0.56)Nb_(0.44))O_(3),i.e.,the equilibrium configuration of B-site cations(Ta and Nb)in the ferroelectric phase.Ta is found to have an off-center displacement of about 0.02A along[001].The off-center displacement of Nb is much larger than that of Ta,thus it makes a major contribution to the occurrence of the ferroelectric instability.
基金the State Key Program for Basic Research of Chinathe Research Found for the Doctoral Program of Higher Education。
文摘A simple double-well potential model is established.It shows that the nature of the low-frequency dielectric constant in ferroelectrics is the additional hopping of the off-center ions in multi-site potential.The co-operative effect causes the fact that the Curie-Weiss law is obeyed.The mechanism of the molecular field is clarified.
