The effect of misfit strain on the electrocaloric effect in polydomain epitaxial BaTi03 thin films at room temper- ature is investigated using the Ginzburg^Landau Devonshire thermodynamic theory. Numerical calculation...The effect of misfit strain on the electrocaloric effect in polydomain epitaxial BaTi03 thin films at room temper- ature is investigated using the Ginzburg^Landau Devonshire thermodynamic theory. Numerical calculations indicate that the misfit strain has a large impact on the ferroelectric polarization states and the electrocaloric effect. Most importantly, the electrocaloric effect in the polydomain ca1/ca2/ca1/ea2 phase is much larger than that in the mon- odomain c phase and the other polydomain phases. Consequently, a large electrocaloric effect can be obtained by carefully controlling the misfit strain, which may provide potential applications in refrigeration devices.展开更多
A Landau-Devonshire thermodynamic theory is employed to investigate the effects of composition and misfit strain on the room-temperature electrocaloric effect of epitaxial Pbl-xSrxTiO3 thin films. The "temperature-mi...A Landau-Devonshire thermodynamic theory is employed to investigate the effects of composition and misfit strain on the room-temperature electrocaloric effect of epitaxial Pbl-xSrxTiO3 thin films. The "temperature-misfit strain" phase diagrams with the Sr composition x of 0.1, 0.3, and 0.5 are constructed. The introduction of Sr composition reduces the Curie temperature greatly, and enhances the electrocaloric effect. Moreover, the electrocaloric effect largely depends on the misfit strain. Therefore, the Sr composition and the misfit strain can be controlled to obtain the giant room-temperature electrocaloric effect.展开更多
The electronic band structures of periodic models for S^H compounds are investigated by the density functional theory. Our results show that the Si H compound changes from indirect-gap semiconductor to direct-gap semi...The electronic band structures of periodic models for S^H compounds are investigated by the density functional theory. Our results show that the Si H compound changes from indirect-gap semiconductor to direct-gap semiconductor with the increase of H content. The density of states, the partial density of states and the atomic charge population are examined in detail to explore the origin of this phenomenon. It is found that the Si-Si bonds are affected by H atoms, which results in the electronic band transformation from indirect gap to direct gap. This is confirmed by the nearest neighbour semi-empirical tight-binding (TB) theory.展开更多
An eighth-order Landau–Devonshire theory is constructed to investigate the piezoelectric and electro–optic properties of tetragonal(1- x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 single crystals(x = 0.38 and x = 0.4). The die...An eighth-order Landau–Devonshire theory is constructed to investigate the piezoelectric and electro–optic properties of tetragonal(1- x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 single crystals(x = 0.38 and x = 0.4). The dielectric stiffness coefficients of the Landau potential are obtained by fitting to the dielectric properties and the phase transition temperature between cubic phase and tetragonal phase. It is indicated that tetragonal(1- x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 single crystals have the firstorder cubic-tetragonal phase transitions. The dielectric constants are in great agreement with the experimental results.The piezoelectric coefficients d33 and d31at room temperature are about 145 p C/N and-62 p C/N respectively which are smaller than that of(1- x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 single crystals around the morphotropic phase boundary.Moreover, tetragonal(1- x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 single crystals have the linear electro–optic coefficients rc =33.7 pm/V and rc = 28.8 pm/V for x = 0.38 and x = 0.4, respectively which are in accordance with the measurements.展开更多
The effect of misfit strain on the electrocaloric effect in polydomain epitaxial BaTiO 3 thin films at room temperature is investigated using the Ginzburg–Landau–Devonshire thermodynamic theory. Numerical calculatio...The effect of misfit strain on the electrocaloric effect in polydomain epitaxial BaTiO 3 thin films at room temperature is investigated using the Ginzburg–Landau–Devonshire thermodynamic theory. Numerical calculations indicate that the misfit strain has a large impact on the ferroelectric polarization states and the electrocaloric effect. Most importantly, the electrocaloric effect in the polydomain ca 1 /ca 2 /ca 1 /ca 2 phase is much larger than that in the monodomain c phase and the other polydomain phases. Consequently, a large electrocaloric effect can be obtained by carefully controlling the misfit strain, which may provide potential applications in refrigeration devices.展开更多
Nickel(Ni)films with positive and negative textured surfaces of lotus and rice leaf patterns were fabricated through an inexpensive and effective method.The as-prepared Ni films were superhydrophobic and exhibited exc...Nickel(Ni)films with positive and negative textured surfaces of lotus and rice leaf patterns were fabricated through an inexpensive and effective method.The as-prepared Ni films were superhydrophobic and exhibited excellent tribological properties after chemical treatment.Experimental results indicated that the water contact angles(WCAs)on the surfaces of biomimetic textured Ni films(approximately 120°)were far greater than those on smooth films(65°).The biomimetic textured surfaces became superhydrophobic(WCA of approximately 150°)after perfluoropolyether(PFPE)treatment,which could be due to the combined effects of the special texture and the PFPE.The as-prepared biomimetic-textured Ni films modified with PFPE were improved with a low friction coefficient and excellent antiwear properties,which were due to the combination of the effective lubrication of PFPE and the special textures that served as a good lubricant and a debris reservoir.Moreover,the antiwear properties of the as-prepared Ni films with negative biomimetic microtextures modified with PFPE were much better than those of films with positive biomimetic microtextures modified with PFPE.展开更多
To study the ferroelectric photovoltaic effect based on polycrystalline films,preparation of high-quality polycrystalline films with low leakage and high remnant polarization is essential.Polycrystalline Bi Fe O3(BFO)...To study the ferroelectric photovoltaic effect based on polycrystalline films,preparation of high-quality polycrystalline films with low leakage and high remnant polarization is essential.Polycrystalline Bi Fe O3(BFO)thin films with extremely large remnant polarization(2Pr=180μC/cm2)were successfully deposited on glass substrates coated with indium tin oxide using a modified radio frequency magnetron sputtering method.Symmetric and asymmetric cells were constructed to investigate the ferroelectric photovoltaic effect in order to understand the relationship between polarization and photovoltaic response.All examined cells showed polarization-induced photovoltaic effect.Our findings also showed that the ferroelectric photovoltaic effect is highly dependent on the material used for the top electrode and the thickness of the polycrystalline film.展开更多
A phenomenological thermodynamic theory is applied to investigate the effect of misfit strain and electric field on the electrocaloric effect of P(VDF-TrFE)/SrTiO 3 bilayer thin films.Theoretical results indicate that...A phenomenological thermodynamic theory is applied to investigate the effect of misfit strain and electric field on the electrocaloric effect of P(VDF-TrFE)/SrTiO 3 bilayer thin films.Theoretical results indicate that the low electric field results in the decrease of the average polarization with the increase of the relative thickness of SrTiO 3 layer,and the high electric field has an opposite effect on it.Moreover,the electrocaloric effect strongly depends on the electric field.The low electric field and the small field change can lead to a maximum of the electrocaloric effect,meanwhile the high electric field or the large field change results in the opposite trend.展开更多
Composition dependence of electrocaloric effect is investigated in(1- x)Pb(Mg1/3Nb2/3)O3- xP b Ti O3 single crystals by using an eighth-order Landau–Devonshire theory. The applied electric field along [001] direction...Composition dependence of electrocaloric effect is investigated in(1- x)Pb(Mg1/3Nb2/3)O3- xP b Ti O3 single crystals by using an eighth-order Landau–Devonshire theory. The applied electric field along [001] direction reduces the ferroelectric-ferroelectric phase transition temperatures, but increases the Curie temperatures. The electrocaloric coefficients of tetragonal phase are much larger than that of rhombohedral and monoclinic phase. A negative electrocaloric effect is observed near the MC-T phase transition in 0.69Pb(Mg1/3Nb2/3)O3-0.31 Pb Ti O3 single crystal. The application of a strong enough electric field results in a high adiabatic temperature change over a broad range of temperature.Therefore, it would be useful to construct a solid state cooling cycle over a broad temperature range for practical applications.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No. 10904053)the Jiangsu Provincial Natural Science Foundation for Colleges and Universities, China (Grant No. 09KJB140002)+1 种基金the Priority Academic Development Program of Jiangsu Higher Education InstitutionsQing Lan Project, China
文摘The effect of misfit strain on the electrocaloric effect in polydomain epitaxial BaTi03 thin films at room temper- ature is investigated using the Ginzburg^Landau Devonshire thermodynamic theory. Numerical calculations indicate that the misfit strain has a large impact on the ferroelectric polarization states and the electrocaloric effect. Most importantly, the electrocaloric effect in the polydomain ca1/ca2/ca1/ea2 phase is much larger than that in the mon- odomain c phase and the other polydomain phases. Consequently, a large electrocaloric effect can be obtained by carefully controlling the misfit strain, which may provide potential applications in refrigeration devices.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10904053)the Natural Science Foundation for Colleges and Universities of Jiangsu Province, China (Grant No. 09KJB140002)the Priority Academic Program Development of Jiangsu Higher Education Institutions and Qing Lan Project
文摘A Landau-Devonshire thermodynamic theory is employed to investigate the effects of composition and misfit strain on the room-temperature electrocaloric effect of epitaxial Pbl-xSrxTiO3 thin films. The "temperature-misfit strain" phase diagrams with the Sr composition x of 0.1, 0.3, and 0.5 are constructed. The introduction of Sr composition reduces the Curie temperature greatly, and enhances the electrocaloric effect. Moreover, the electrocaloric effect largely depends on the misfit strain. Therefore, the Sr composition and the misfit strain can be controlled to obtain the giant room-temperature electrocaloric effect.
基金supported by the National Natural Science Foundation of China (Grant No. 50775101)the New Century Excellent Talents (Grant No. NCET-04-0515)+2 种基金the Jiangsu Provincial Science and Technology Supporting Project,China (Grant No. BE2008030)Qing Lan Project (2008-04)Jiangsu University Natural Science Foundation of China (Grant No. 07KJB430023)
文摘The electronic band structures of periodic models for S^H compounds are investigated by the density functional theory. Our results show that the Si H compound changes from indirect-gap semiconductor to direct-gap semiconductor with the increase of H content. The density of states, the partial density of states and the atomic charge population are examined in detail to explore the origin of this phenomenon. It is found that the Si-Si bonds are affected by H atoms, which results in the electronic band transformation from indirect gap to direct gap. This is confirmed by the nearest neighbour semi-empirical tight-binding (TB) theory.
基金Project supported by the National Natural Science Foundation of China(Grant No.51335002)the Changzhou Science and Technology Project,China(Grant No.CJ20130022)the Priority Academic Program Development of Jiangsu Higher Education Institutions,China
文摘An eighth-order Landau–Devonshire theory is constructed to investigate the piezoelectric and electro–optic properties of tetragonal(1- x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 single crystals(x = 0.38 and x = 0.4). The dielectric stiffness coefficients of the Landau potential are obtained by fitting to the dielectric properties and the phase transition temperature between cubic phase and tetragonal phase. It is indicated that tetragonal(1- x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 single crystals have the firstorder cubic-tetragonal phase transitions. The dielectric constants are in great agreement with the experimental results.The piezoelectric coefficients d33 and d31at room temperature are about 145 p C/N and-62 p C/N respectively which are smaller than that of(1- x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 single crystals around the morphotropic phase boundary.Moreover, tetragonal(1- x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 single crystals have the linear electro–optic coefficients rc =33.7 pm/V and rc = 28.8 pm/V for x = 0.38 and x = 0.4, respectively which are in accordance with the measurements.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10904053)the Jiangsu Provincial Natural Science Foundation for Colleges and Universities, China (Grant No. 09KJB140002)+1 种基金the Priority Academic Development Program of Jiangsu Higher Education InstitutionsQing Lan Project, China
文摘The effect of misfit strain on the electrocaloric effect in polydomain epitaxial BaTiO 3 thin films at room temperature is investigated using the Ginzburg–Landau–Devonshire thermodynamic theory. Numerical calculations indicate that the misfit strain has a large impact on the ferroelectric polarization states and the electrocaloric effect. Most importantly, the electrocaloric effect in the polydomain ca 1 /ca 2 /ca 1 /ca 2 phase is much larger than that in the monodomain c phase and the other polydomain phases. Consequently, a large electrocaloric effect can be obtained by carefully controlling the misfit strain, which may provide potential applications in refrigeration devices.
基金The authors appreciate the National Natural Science Foundation of China(Nos.51102028 and 51335002)acknowledge the financial support of the Priority Academic Program Development of Jiangsu Higher Education Institutions.
文摘Nickel(Ni)films with positive and negative textured surfaces of lotus and rice leaf patterns were fabricated through an inexpensive and effective method.The as-prepared Ni films were superhydrophobic and exhibited excellent tribological properties after chemical treatment.Experimental results indicated that the water contact angles(WCAs)on the surfaces of biomimetic textured Ni films(approximately 120°)were far greater than those on smooth films(65°).The biomimetic textured surfaces became superhydrophobic(WCA of approximately 150°)after perfluoropolyether(PFPE)treatment,which could be due to the combined effects of the special texture and the PFPE.The as-prepared biomimetic-textured Ni films modified with PFPE were improved with a low friction coefficient and excellent antiwear properties,which were due to the combination of the effective lubrication of PFPE and the special textures that served as a good lubricant and a debris reservoir.Moreover,the antiwear properties of the as-prepared Ni films with negative biomimetic microtextures modified with PFPE were much better than those of films with positive biomimetic microtextures modified with PFPE.
基金supported by the National High Technology Research and Development Program(Grant No.2011AA050511)Jiangsu"333"Project,the Priority Academic Program Development of Jiangsu Higher Education Institutions and Research and Innovation Project for College Graduates of Jiangsu Province(Grant No.CXLX13_722)
文摘To study the ferroelectric photovoltaic effect based on polycrystalline films,preparation of high-quality polycrystalline films with low leakage and high remnant polarization is essential.Polycrystalline Bi Fe O3(BFO)thin films with extremely large remnant polarization(2Pr=180μC/cm2)were successfully deposited on glass substrates coated with indium tin oxide using a modified radio frequency magnetron sputtering method.Symmetric and asymmetric cells were constructed to investigate the ferroelectric photovoltaic effect in order to understand the relationship between polarization and photovoltaic response.All examined cells showed polarization-induced photovoltaic effect.Our findings also showed that the ferroelectric photovoltaic effect is highly dependent on the material used for the top electrode and the thickness of the polycrystalline film.
基金Supported by the National Natural Science Foundation of China under Grant No. 10904053Sponsored by the Priority Academic Program Development of Jiangsu Higher Education Institutions and Qing Lan Project
文摘A phenomenological thermodynamic theory is applied to investigate the effect of misfit strain and electric field on the electrocaloric effect of P(VDF-TrFE)/SrTiO 3 bilayer thin films.Theoretical results indicate that the low electric field results in the decrease of the average polarization with the increase of the relative thickness of SrTiO 3 layer,and the high electric field has an opposite effect on it.Moreover,the electrocaloric effect strongly depends on the electric field.The low electric field and the small field change can lead to a maximum of the electrocaloric effect,meanwhile the high electric field or the large field change results in the opposite trend.
基金Supported by the State Key Program of National Natural Science of China under Grant No.51335002Changzhou Science and Technology Project under Grant No.CJ20130022the Priority Academic Program Development of Jiangsu Higher Education Institutions on Renewable Energy Material Science and Engineering
文摘Composition dependence of electrocaloric effect is investigated in(1- x)Pb(Mg1/3Nb2/3)O3- xP b Ti O3 single crystals by using an eighth-order Landau–Devonshire theory. The applied electric field along [001] direction reduces the ferroelectric-ferroelectric phase transition temperatures, but increases the Curie temperatures. The electrocaloric coefficients of tetragonal phase are much larger than that of rhombohedral and monoclinic phase. A negative electrocaloric effect is observed near the MC-T phase transition in 0.69Pb(Mg1/3Nb2/3)O3-0.31 Pb Ti O3 single crystal. The application of a strong enough electric field results in a high adiabatic temperature change over a broad range of temperature.Therefore, it would be useful to construct a solid state cooling cycle over a broad temperature range for practical applications.