The elastocalorie effect of PbTiO3 thin films with 180° domain structure is studied using the phase field method. The influence of external stress σ33, misfit strain μm and domain wall energy on the adiabatic t...The elastocalorie effect of PbTiO3 thin films with 180° domain structure is studied using the phase field method. The influence of external stress σ33, misfit strain μm and domain wall energy on the adiabatic temperature change （ △ Tσ） at room temperature are carried out. The calculation results indicate that ｜△Tσ｜ increases as ｜σ33｜ or ｜μm｜ increases. The largest △ Tσ wlue of--7.81（ is obtained at σ33 = 2 GPa and Um =-0.02. Furthermore, the domain switching behaviors under different gradient coeffcients are different, and finally affect the elastocaloric effect in PTO thin films. These results could provide a guide to choose the substrate and the preparation process in experiments.展开更多
The effects of pressure on phonon modes of ferroeleetrie tetragonal P4mm and paraelectric cubic Pm3m PbTiOa are systematically investigated by using first-principles simulations. The pressure-induced tetragonal-to-cub...The effects of pressure on phonon modes of ferroeleetrie tetragonal P4mm and paraelectric cubic Pm3m PbTiOa are systematically investigated by using first-principles simulations. The pressure-induced tetragonal-to-cubie and subsequent cubic-to-tetragonal phase transitions are the second-order transitions, which are different from the phase transitions induced by temperature [Phys. Rev. Lett. 25 （1970） 167]. As pressure increases, the lowest A1 and E modes of the tetragonal phase become softer and converge to the F1u mode of the cubic phase. As pressure further increases, the lowest Flu mode first hardens and then softens again, and finally diverges into A1 and E modes. The behaviors of optical phonon modes confirm the ferroelectric-to-paraelectric-to-ferroeleetric phase transitions.展开更多
Properties of ferroelectric xBiInO3-（1-x）PbTiO3（xBI-（1-x）PT） thin films deposited on（101） SrRuO3/（200）Pt/（200） MgO substrates by rf magnetron sputtering method and effects of deposition conditions are inve...Properties of ferroelectric xBiInO3-（1-x）PbTiO3（xBI-（1-x）PT） thin films deposited on（101） SrRuO3/（200）Pt/（200） MgO substrates by rf magnetron sputtering method and effects of deposition conditions are investigated.The structures of the xBI-（1-x）PT films are characterized by x-ray diffraction and scanning electron microscopy.The results indicate that the thin films are grown with mainly（001） orientation. The chemical compositions of the films are analyzed by scanning electron probe and the results indicate that the loss phenomena of Pb and Bi elements depend on the pressure and temperature during the sputtering process.The sputtering parameters including target composition, substrate temperature, and gas pressure are adjusted to obtain optimum sputtering conditions. To decrease leakage currents,2 mol% La2 O3 is doped in the targets. The P-E hysteresis loops show that the optimized xBI-（1-x）PT（x = 0.24） film has high ferroelectricities with remnant polarization2 Pr = 80μC/cm2 and coercive electric field 2 EC = 300 kV/cm. The Curie temperature is about 640℃. The results show that the films have optimum performance and will have wide applications.展开更多
PbTiO3 is a simple but very important ferroelectric oxide that has been extensively studied and widely used in various technological applications. However, most previous studies and applications were based on the bulk...PbTiO3 is a simple but very important ferroelectric oxide that has been extensively studied and widely used in various technological applications. However, most previous studies and applications were based on the bulk material or the conventional [001]-orientated films. There are few studies on PbTiO3 films grown along other crystalline axes. In this study, a first-principles calculation was performed to compute the polarization of PbTiO3 films strained by SrTiO3 and LaAlO3 substrates. Our results show that the polarization of PbTiO3 films strongly depends on the growth orientation as well as the monoclinic angles. Further, it is suggested that the ferroelectricity of PbTiO3 mainly depends on the tetragonality of the lattice, instead of the simple strain.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 11502078 and 11402222the General Project of Hunan Provincial Department of Education under Grant No 15C0535the Start-up Foundation of High-talent Research Project of Hunan University of Science and Technology under Grant No E51517
文摘The elastocalorie effect of PbTiO3 thin films with 180° domain structure is studied using the phase field method. The influence of external stress σ33, misfit strain μm and domain wall energy on the adiabatic temperature change （ △ Tσ） at room temperature are carried out. The calculation results indicate that ｜△Tσ｜ increases as ｜σ33｜ or ｜μm｜ increases. The largest △ Tσ wlue of--7.81（ is obtained at σ33 = 2 GPa and Um =-0.02. Furthermore, the domain switching behaviors under different gradient coeffcients are different, and finally affect the elastocaloric effect in PTO thin films. These results could provide a guide to choose the substrate and the preparation process in experiments.
基金Supported by the Fundamental Research Funds for the Central Universities under Grant No 2013RC19
文摘The effects of pressure on phonon modes of ferroeleetrie tetragonal P4mm and paraelectric cubic Pm3m PbTiOa are systematically investigated by using first-principles simulations. The pressure-induced tetragonal-to-cubie and subsequent cubic-to-tetragonal phase transitions are the second-order transitions, which are different from the phase transitions induced by temperature [Phys. Rev. Lett. 25 （1970） 167]. As pressure increases, the lowest A1 and E modes of the tetragonal phase become softer and converge to the F1u mode of the cubic phase. As pressure further increases, the lowest Flu mode first hardens and then softens again, and finally diverges into A1 and E modes. The behaviors of optical phonon modes confirm the ferroelectric-to-paraelectric-to-ferroeleetric phase transitions.
基金Supported by the National Natural Science Foundation of China under Grant No 11304160the Special Fund for Public Interest of China under Grant No 201510068,and the NUPTFC under Grant No NY215111
文摘Properties of ferroelectric xBiInO3-（1-x）PbTiO3（xBI-（1-x）PT） thin films deposited on（101） SrRuO3/（200）Pt/（200） MgO substrates by rf magnetron sputtering method and effects of deposition conditions are investigated.The structures of the xBI-（1-x）PT films are characterized by x-ray diffraction and scanning electron microscopy.The results indicate that the thin films are grown with mainly（001） orientation. The chemical compositions of the films are analyzed by scanning electron probe and the results indicate that the loss phenomena of Pb and Bi elements depend on the pressure and temperature during the sputtering process.The sputtering parameters including target composition, substrate temperature, and gas pressure are adjusted to obtain optimum sputtering conditions. To decrease leakage currents,2 mol% La2 O3 is doped in the targets. The P-E hysteresis loops show that the optimized xBI-（1-x）PT（x = 0.24） film has high ferroelectricities with remnant polarization2 Pr = 80μC/cm2 and coercive electric field 2 EC = 300 kV/cm. The Curie temperature is about 640℃. The results show that the films have optimum performance and will have wide applications.
基金Acknowledgements The work was supported by the National Natural Science Foundation of China （Grant Nos. 51322206 and 11274060） and the Natural Science Foundation of Jiangsu Province of China （Grant No. BK20141329）.
文摘PbTiO3 is a simple but very important ferroelectric oxide that has been extensively studied and widely used in various technological applications. However, most previous studies and applications were based on the bulk material or the conventional [001]-orientated films. There are few studies on PbTiO3 films grown along other crystalline axes. In this study, a first-principles calculation was performed to compute the polarization of PbTiO3 films strained by SrTiO3 and LaAlO3 substrates. Our results show that the polarization of PbTiO3 films strongly depends on the growth orientation as well as the monoclinic angles. Further, it is suggested that the ferroelectricity of PbTiO3 mainly depends on the tetragonality of the lattice, instead of the simple strain.
