In this article, distributions of internal stress and internal electric fields around a triple point of ferroelectric polycrystals generated by the spontaneous deformation and spontaneous polarization were investigate...In this article, distributions of internal stress and internal electric fields around a triple point of ferroelectric polycrystals generated by the spontaneous deformation and spontaneous polarization were investigated. It was found that when all three grains consist of a single domain, the internal stresses and the internal electric fields do not vanish. Though it may be determined according to the principle of energy, the spontaneous configuration will not be unique without involving other conditions due to the symmetry of the crystal structure.展开更多
The ferroelectric domain formation(FDF) and polarization switching(FDPS) subjected to an external electric field are simulated using the phase-field(PF) method,and the FDPS mechanism under different external electric ...The ferroelectric domain formation(FDF) and polarization switching(FDPS) subjected to an external electric field are simulated using the phase-field(PF) method,and the FDPS mechanism under different external electric fields is discussed.The results show that the FDF is a process of nucleation and growth in ferroelectric without applying any external stress.Four kinds of parallelogram shaped ferroelectric domains are formed at the steady state,in which the 180° anti-phase domains regularly align along the 45° direction and the 90° anti-phase domains regularly distribute like a stepladder.Steady electric fields can rotate domain polarization by 90° and 180°,and force the orientation-favorite domains and the average polarization to grow into larger ones.The greater the steady electric field,the larger the average polarization at the steady state.In ferroelectrics subject to an alternating electric field,domain polarization switches to cause a hysteresis loop and an associated butterfly loop with the alternating electric field.The coercive field and remnant field are enhanced with the increase of the electric field frequency or strength,or with the decrease of temperature.展开更多
The incompatibility of the spontaneous polarization across the interface between two grains may induce internal stress and electric fields in a ferroelectric body. The built up of stresses and electric fields may ser...The incompatibility of the spontaneous polarization across the interface between two grains may induce internal stress and electric fields in a ferroelectric body. The built up of stresses and electric fields may seriously affect the functioning of ferroelectric materials. In this article, the effects of the incompatibility of the spontaneous polarization for various types of interfaces on the electric fields are discussed. Numerical results indicate that the incompatibility of the spontaneous polarization may result in the electric field being unbounded when the interface does not have a continuous normal.展开更多
We have performed the first-principles calculation to investigate the origins of ferroelectricities and different po- larization behaviours of superlattices BaTiO3/SrTiO3 and PbTiO3/SrTiO3. The density of state （DOS...We have performed the first-principles calculation to investigate the origins of ferroelectricities and different po- larization behaviours of superlattices BaTiO3/SrTiO3 and PbTiO3/SrTiO3. The density of state （DOS） and electronic charge profiles show that there are strong hybridizations between atoms Ti and O and between atoms Pb and O which play very important roles in producing the ferroelectricities of superlattices BaTiO3/SrTiO3 and PbTiO3/SrTiO3. Ow- ing to the decline of internal electric field in SrTiO3 （ST） layer, the tetragonality and polarizations of superlattices decrease with increasing the fraction of SrTiO3 in the superlattices. We find that the polarization of PbTiO3/SrTiO3 is largerthan that of BaTiO3/SrTiO3 at the same ratio of components, because the polarization mismatch between PbTiO3 and SrTiO3 is larger than that between BaTiO3 and SrTiO3. The polarization and tetragonality are en- hanced with respect to those of bulk tetragonal BaTiO3 in the superlattices BaTiO3/SrTiO3, while the polarization and tetragonality are reduced with respect to those of bulk tetragonal PbTiO3 in superlattices PbTiO3/SrTiO3.展开更多
Ferroelectric materials, with spontaneous electric polarization that can be reversed by an external electric field, have many technological applications, such as non-volatile memories, field-effect transistors, and se...Ferroelectric materials, with spontaneous electric polarization that can be reversed by an external electric field, have many technological applications, such as non-volatile memories, field-effect transistors, and sensors. Ferroelectric polarization originates from an asymmetric distribution of atoms in a material’s crystal structure, requiring the material to have two energetically degenerate ground state structures (two stable spontaneous polarization states) with inversion symmetry breaking[1].展开更多
基金National Natural Science Foundation of China(No.19672053)Special Funds for Doctoral Programs(No.96061305)
文摘In this article, distributions of internal stress and internal electric fields around a triple point of ferroelectric polycrystals generated by the spontaneous deformation and spontaneous polarization were investigated. It was found that when all three grains consist of a single domain, the internal stresses and the internal electric fields do not vanish. Though it may be determined according to the principle of energy, the spontaneous configuration will not be unique without involving other conditions due to the symmetry of the crystal structure.
基金supported by the National Natural Science Foundation of China(Grant Nos.51075335,51174168,10902086,and 50875217)the NPU Foundation for Fundamental Research(Grant No.JC201005)
文摘The ferroelectric domain formation(FDF) and polarization switching(FDPS) subjected to an external electric field are simulated using the phase-field(PF) method,and the FDPS mechanism under different external electric fields is discussed.The results show that the FDF is a process of nucleation and growth in ferroelectric without applying any external stress.Four kinds of parallelogram shaped ferroelectric domains are formed at the steady state,in which the 180° anti-phase domains regularly align along the 45° direction and the 90° anti-phase domains regularly distribute like a stepladder.Steady electric fields can rotate domain polarization by 90° and 180°,and force the orientation-favorite domains and the average polarization to grow into larger ones.The greater the steady electric field,the larger the average polarization at the steady state.In ferroelectrics subject to an alternating electric field,domain polarization switches to cause a hysteresis loop and an associated butterfly loop with the alternating electric field.The coercive field and remnant field are enhanced with the increase of the electric field frequency or strength,or with the decrease of temperature.
文摘The incompatibility of the spontaneous polarization across the interface between two grains may induce internal stress and electric fields in a ferroelectric body. The built up of stresses and electric fields may seriously affect the functioning of ferroelectric materials. In this article, the effects of the incompatibility of the spontaneous polarization for various types of interfaces on the electric fields are discussed. Numerical results indicate that the incompatibility of the spontaneous polarization may result in the electric field being unbounded when the interface does not have a continuous normal.
基金Project supported by the National Natural Science Foundation of China （Grant Nos 10572155, 10172030 and 50232030）.
文摘We have performed the first-principles calculation to investigate the origins of ferroelectricities and different po- larization behaviours of superlattices BaTiO3/SrTiO3 and PbTiO3/SrTiO3. The density of state （DOS） and electronic charge profiles show that there are strong hybridizations between atoms Ti and O and between atoms Pb and O which play very important roles in producing the ferroelectricities of superlattices BaTiO3/SrTiO3 and PbTiO3/SrTiO3. Ow- ing to the decline of internal electric field in SrTiO3 （ST） layer, the tetragonality and polarizations of superlattices decrease with increasing the fraction of SrTiO3 in the superlattices. We find that the polarization of PbTiO3/SrTiO3 is largerthan that of BaTiO3/SrTiO3 at the same ratio of components, because the polarization mismatch between PbTiO3 and SrTiO3 is larger than that between BaTiO3 and SrTiO3. The polarization and tetragonality are en- hanced with respect to those of bulk tetragonal BaTiO3 in the superlattices BaTiO3/SrTiO3, while the polarization and tetragonality are reduced with respect to those of bulk tetragonal PbTiO3 in superlattices PbTiO3/SrTiO3.
文摘Ferroelectric materials, with spontaneous electric polarization that can be reversed by an external electric field, have many technological applications, such as non-volatile memories, field-effect transistors, and sensors. Ferroelectric polarization originates from an asymmetric distribution of atoms in a material’s crystal structure, requiring the material to have two energetically degenerate ground state structures (two stable spontaneous polarization states) with inversion symmetry breaking[1].
