In the present work, the phase transitions and relaxor behavior of (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT, x = 0.2―0.4) ferroelectric ceramics have been investigated by means of X-ray diffraction, di-electric spectros...In the present work, the phase transitions and relaxor behavior of (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT, x = 0.2―0.4) ferroelectric ceramics have been investigated by means of X-ray diffraction, di-electric spectroscopy, the P-E hysteresis loop measurements and Raman scattering techniques. Structural analysis revealed that with the increase of PbTiO3 content, PMN-PT ceramics experienced a gradual phase transition process from rhombohedral to tetragonal. It is usually believed that such kinds of phase transitions resulted in the linear decrease of relaxation degree. Surprisingly, our analysis of the dielectric spectra revealed that the indicator of the degree of diffuseness γ reached the maximum value near morphotropic phase boundary (MPB) (x = 0.32), then decreased with the further increase of PbTiO3 content. The large dielectric relaxor feature near MPB may be attributed to the for-mation of ordered nanodomains, resulting from complex coexisting nanostructures. Further, the P-E hysteresis loop measurements and Raman analysis of the B-site cation order correlated well with the dielectric measurement results. It was found that the hysteresis loop squareness Rsq received the minimum value while the inverse of the value of full wide of half maximum (FWHM) of A1g mode reached the maximum value at MPB composition, which showed similar trends to γ.展开更多
We have investigated the temperature dependence of elastic modulus for various ferroelectric ceramics in the temperature range of 20–90°C.The Na0.5Bi0.5TiO3(NBT)ceramics has a phase transition at 200°C,thus...We have investigated the temperature dependence of elastic modulus for various ferroelectric ceramics in the temperature range of 20–90°C.The Na0.5Bi0.5TiO3(NBT)ceramics has a phase transition at 200°C,thus exhibits minimal change in elastic modulus up to 90°C,while the elastic modulus of the BaZr0.07Ti0.93O3(BZT-7)shows 12.5%change at the phase transition temperature of70°C and that of the BaZr0.15Ti0.85O3(BZT-15)ceramics shows 34.6%change at the phase transition temperature of60°C.The variations of elastic modulus will affect the temperature stability of devices made by these lead-free ferroelectric ceramics.展开更多
Thermally activated dislocation emission in high-temperature ferroelectric ceramics is investigated through an assumption of thermal stability and a novel analytical method. The stress intensity factor (SIF) arising f...Thermally activated dislocation emission in high-temperature ferroelectric ceramics is investigated through an assumption of thermal stability and a novel analytical method. The stress intensity factor (SIF) arising from domain switching is evaluated by using a Green's function method, and the critical applied electric field intensity factor (CAEFIF) for brittle fracture at room temperature is obtained. Besides, the lowest temperature for single dislocation emission before brittle fracture is also obtained by constructing an energy balance. The multi-scale analysis of facture toughness of the ferroelectric ceramics at high temperature is carried out. Through the analysis, the CAEFIF for crack extension is recalculated. The results show that the competition and interaction effects between dislocation emission and brittle fracture are very obvious. Besides, the higher critical activation temperature, the more columns of obstacles will be overcome. Additionally, the shielding effect arising from thermally activated dislocations is remarkable, thus, the brittle-ductile transition can promote the fracture toughness of high-temperature ferroelectric ceramics.展开更多
基金Supported by the National Natural Science Foundation of China (Grant No. 60601020)Project of New Star of Science and Technology of Beijing (Grant No. 2007A014)+1 种基金Natural Science Foundation of Beijing (Grant No. 4072006)Science and Technology Development Project of Beijing Education Committee (Grant No. KM200810005012)
文摘In the present work, the phase transitions and relaxor behavior of (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT, x = 0.2―0.4) ferroelectric ceramics have been investigated by means of X-ray diffraction, di-electric spectroscopy, the P-E hysteresis loop measurements and Raman scattering techniques. Structural analysis revealed that with the increase of PbTiO3 content, PMN-PT ceramics experienced a gradual phase transition process from rhombohedral to tetragonal. It is usually believed that such kinds of phase transitions resulted in the linear decrease of relaxation degree. Surprisingly, our analysis of the dielectric spectra revealed that the indicator of the degree of diffuseness γ reached the maximum value near morphotropic phase boundary (MPB) (x = 0.32), then decreased with the further increase of PbTiO3 content. The large dielectric relaxor feature near MPB may be attributed to the for-mation of ordered nanodomains, resulting from complex coexisting nanostructures. Further, the P-E hysteresis loop measurements and Raman analysis of the B-site cation order correlated well with the dielectric measurement results. It was found that the hysteresis loop squareness Rsq received the minimum value while the inverse of the value of full wide of half maximum (FWHM) of A1g mode reached the maximum value at MPB composition, which showed similar trends to γ.
基金supported by the National Basic Research Program of China (2012CB921504, 2011CB707902)the National Natural Science Foundation of China (11074122)+2 种基金Fundamental Research Funds for the Central Universities (1113020403, 1101020402)State Key Laboratory of Acoustics, Chinese Academy of Sciences (SKLA201207)the Priority Academic Program Development of Jiangsu Higher Education Institutions and SRF for ROCS, SEM and Project of Interdisciplinary Center of Nanjing University
文摘We have investigated the temperature dependence of elastic modulus for various ferroelectric ceramics in the temperature range of 20–90°C.The Na0.5Bi0.5TiO3(NBT)ceramics has a phase transition at 200°C,thus exhibits minimal change in elastic modulus up to 90°C,while the elastic modulus of the BaZr0.07Ti0.93O3(BZT-7)shows 12.5%change at the phase transition temperature of70°C and that of the BaZr0.15Ti0.85O3(BZT-15)ceramics shows 34.6%change at the phase transition temperature of60°C.The variations of elastic modulus will affect the temperature stability of devices made by these lead-free ferroelectric ceramics.
基金Supported by the Ph.D. Programs Foundation of Ministry of Education of China under Grant No. 20123305120008, the Scientific Research Project of Department of Education of Zhejiang Province under Grant No. Y201223508, a Grant from the Impact and Safety of Coastal Engineering Initiative, a COE Program of Zhejiang Provincial Government at Ningbo University under Grant Nos. zj1117, zj1203, and zj1201 and the K.C. Wong Magana Fund
文摘Thermally activated dislocation emission in high-temperature ferroelectric ceramics is investigated through an assumption of thermal stability and a novel analytical method. The stress intensity factor (SIF) arising from domain switching is evaluated by using a Green's function method, and the critical applied electric field intensity factor (CAEFIF) for brittle fracture at room temperature is obtained. Besides, the lowest temperature for single dislocation emission before brittle fracture is also obtained by constructing an energy balance. The multi-scale analysis of facture toughness of the ferroelectric ceramics at high temperature is carried out. Through the analysis, the CAEFIF for crack extension is recalculated. The results show that the competition and interaction effects between dislocation emission and brittle fracture are very obvious. Besides, the higher critical activation temperature, the more columns of obstacles will be overcome. Additionally, the shielding effect arising from thermally activated dislocations is remarkable, thus, the brittle-ductile transition can promote the fracture toughness of high-temperature ferroelectric ceramics.
