In recent years,the perovskite solar cells have gained much attention because of their ever-increasing power conversion efficiency(PCE),simple solution fabrication process,flyable,light-weight wearable and deployable ...In recent years,the perovskite solar cells have gained much attention because of their ever-increasing power conversion efficiency(PCE),simple solution fabrication process,flyable,light-weight wearable and deployable for ultra-lightweight space and low-cost materials constituents etc.Over the last few years,the efficiency of perovskite solar cells has surpassed 25%due to high-quality perovskite-film accomplished through low-temperature synthesis techniques along with developing suitable interface and electrode-materials.Besides,the stability of perovskite solar cells has attracted much well-deserved attention.In this article we have focused on recent progress of the perovskite solar cells regarding their crystallinity,morphology and synthesis techniques.Also,demonstrated different layers such as electron transport-layers(ETLs),hole transport-layers(HTLs)and buffer-layers utilized in perovskite solar-cells,considering their band gap,carrier mobility,transmittance etc.Outlook of various tin(Sn),carbon and polymer-based perovskite solar cells and their potential of commercialization feasibility has also been discussed.展开更多
The solid solutions of(1-x)LaFeO_(3–x)BaTiO_(3)(0.0≤x≤0.25)have been synthesized successfully by the conventional solid-state reaction method.Room temperature(RT)X-ray diffraction studies reveal the stabilization o...The solid solutions of(1-x)LaFeO_(3–x)BaTiO_(3)(0.0≤x≤0.25)have been synthesized successfully by the conventional solid-state reaction method.Room temperature(RT)X-ray diffraction studies reveal the stabilization of orthorhombic phase with Pbnm space group.Complete solubility in the perovskite series was demonstrated up to x=0.25.The dielectric permittivity shows colossal dielectric constant(CDC)at RT.The doping of BaTiO_(3)in LaFeO_(3)exhibit pronounced CDC up to a composition x=0.15,further it starts to decrease.The frequency-dependent dielectric loss exhibits polaronic conduction,which can attribute to presence of multiple valence of iron.The relaxation frequency and polaronic conduction mechanism was shifted towards RT as function of x.Moreover,large magnetic moment with weak ferromagnetic behavior is observed in doped LaFeO_(3) solid solution,which might be the destruction of spin cycloid structure due to insertion of Ti in Fe–O–Fe network of LaFeO_(3).展开更多
We studied forest vegetation at Lata-Tolma- Phagti, a protected area and part of Nanda Devi Biosphere Reserve in the western Himalaya. We analyzed community composition, population structure, regeneration patterns, an...We studied forest vegetation at Lata-Tolma- Phagti, a protected area and part of Nanda Devi Biosphere Reserve in the western Himalaya. We analyzed community composition, population structure, regeneration patterns, and projected development of future compositional patterns. We sampled ten 10 x 10 m quadrat for tree species in each of 30 forest stands. We sampled shrubs in ten 5 x 5 m quadrat, and herbs in twenty 1 x 1 m quadrat within each forest stand. We recorded 248 plant species from 8 forest communities. Broadly the demographic profiles at study sites exhibited progressive structures suggesting long term persistence of the communities/species. Density--diameter distribution revealed greater proportions of seedlings and a significant decline （P 〈 0.05） in the proportion of trees in older age/size classes. Of the 23 recorded tree species, 13.0 % showed good, 52.2 % fair, 26.1% poor and 8.7 % no regeneration. Differences in regeneration by species are indicative of future foreststructure and dynamics. Assessment of changes in structure of forest types provides baseline data for development of priorities for conservation of other representative land- scapes in the reserve as well as in the Himalaya.展开更多
Lead-free x(0.50(Ba_(0.7)Ca_(0.3)TiO_(3)-0.50Ba(Zr_(0.2)Ti_(0.8)O_(3)-(1-x)PVDF ceramic–polymer nanocomposites with x=0.025,0.05,0.10,0.15,0.20,0.25 were prepared using melt-mixing technique.The distribution of nanoc...Lead-free x(0.50(Ba_(0.7)Ca_(0.3)TiO_(3)-0.50Ba(Zr_(0.2)Ti_(0.8)O_(3)-(1-x)PVDF ceramic–polymer nanocomposites with x=0.025,0.05,0.10,0.15,0.20,0.25 were prepared using melt-mixing technique.The distribution of nanoceramic filler particles(0.50(Ba_(0.7)Ca_(0.3)TiO_(3)-0.50Ba(Zr_(0.2)Ti_(0.8)O_(3)in the PVDF matrix were examined using scanning electron microscope.Impedance analysis indicated the negative temperature coefficient of resistance character of all the test specimens.Filler concentrationdependent piezoelectric coefficient(d33Þdata followed exponential growth types of variation.The data for ac conductivity were found to obey Jonscher’s power law.The correlated barrier hopping(CBH)model was found to explain the mechanism of charge transport occurring in the system.The low value of loss tangent(-10^(-2))along with the high value of d_(33) foreshadowing the prospect of present nanocomposite is a better nonlead option for piezo-sensing/detection applications,especially in bio-medical area.展开更多
Lead-free Ba(Fe_(1/2)Nb_(1/2))O_(3)/PVDF O_(3) composites were fabricated using melt.mixing technique.X-ray diffraction,scanning electron microscopy,dielectric,impedance,ac conductivity,magnetic force microscopy(MFM)a...Lead-free Ba(Fe_(1/2)Nb_(1/2))O_(3)/PVDF O_(3) composites were fabricated using melt.mixing technique.X-ray diffraction,scanning electron microscopy,dielectric,impedance,ac conductivity,magnetic force microscopy(MFM)and vibrating sample magne-tometer studies were undertaken to characterize the samples.Average crstallite size of the Ba(Fe_(1/2)Nb_(1/2))O_(3) powder,estimated using Williamson-Hall approach,was found to be~42 nm.The fller particles of~0.5-1 pum were found to disperse in the polymer matrix of all the composites.Filler concentration dependent values of real and imaginary parts of complex permittivity showed increasing trend and were seen to follow Bruggeman and Furukawa equations.The data for ac conductivity exhibited negative temperature coeficient of resistance character of the test materials and were found to obey Jonscher's power law.The correlated barier hopping model was found to explain satisfactorily the mechanism of charge transport occurring in the system.MFM confirmed the presence of magnetic phases in the composites.Typical magnetization versus applied field curves indicated the possibility of magnetoelectric coupling in the system.Hence,the present composites have shown themselves as potential multi-functional candidate materials for use in high density data storage applications.展开更多
Temperature dependent X-ray diffraction(XRD)and dielectric properties of perovskite Ba(Zr_(0.2)Ti_(0.8))O_(3) ceramic prepared using a standard solid-state reaction process is presented.Along with phase transitions at...Temperature dependent X-ray diffraction(XRD)and dielectric properties of perovskite Ba(Zr_(0.2)Ti_(0.8))O_(3) ceramic prepared using a standard solid-state reaction process is presented.Along with phase transitions at low temperature,a new phase transition at high temperature(873℃ at 20 Hz),diffusive in character has been found where the lattice structure changes from monoclinic(space group:P2=m) to hexagonal(space group:P6=mmm).This result places present ceramic in the list of potential candidate for intended high temperature applications.The AC conductivity data followed hopping type charge conduction and supports jump relaxation model.The experimental value of d_(33)=98 pC/N was found.The dependence of polarization and strain on electric field at room temperature suggested that lead-free Ba(Zr_(0.2)Ti_(0.8))O_(3) is a promising material for electrostrictive applications.展开更多
文摘In recent years,the perovskite solar cells have gained much attention because of their ever-increasing power conversion efficiency(PCE),simple solution fabrication process,flyable,light-weight wearable and deployable for ultra-lightweight space and low-cost materials constituents etc.Over the last few years,the efficiency of perovskite solar cells has surpassed 25%due to high-quality perovskite-film accomplished through low-temperature synthesis techniques along with developing suitable interface and electrode-materials.Besides,the stability of perovskite solar cells has attracted much well-deserved attention.In this article we have focused on recent progress of the perovskite solar cells regarding their crystallinity,morphology and synthesis techniques.Also,demonstrated different layers such as electron transport-layers(ETLs),hole transport-layers(HTLs)and buffer-layers utilized in perovskite solar-cells,considering their band gap,carrier mobility,transmittance etc.Outlook of various tin(Sn),carbon and polymer-based perovskite solar cells and their potential of commercialization feasibility has also been discussed.
文摘The solid solutions of(1-x)LaFeO_(3–x)BaTiO_(3)(0.0≤x≤0.25)have been synthesized successfully by the conventional solid-state reaction method.Room temperature(RT)X-ray diffraction studies reveal the stabilization of orthorhombic phase with Pbnm space group.Complete solubility in the perovskite series was demonstrated up to x=0.25.The dielectric permittivity shows colossal dielectric constant(CDC)at RT.The doping of BaTiO_(3)in LaFeO_(3)exhibit pronounced CDC up to a composition x=0.15,further it starts to decrease.The frequency-dependent dielectric loss exhibits polaronic conduction,which can attribute to presence of multiple valence of iron.The relaxation frequency and polaronic conduction mechanism was shifted towards RT as function of x.Moreover,large magnetic moment with weak ferromagnetic behavior is observed in doped LaFeO_(3) solid solution,which might be the destruction of spin cycloid structure due to insertion of Ti in Fe–O–Fe network of LaFeO_(3).
基金supported by DST SB/YS/LS-205/2013CSIR(09/560(0015)/2011-EMRI),Govt.of India
文摘We studied forest vegetation at Lata-Tolma- Phagti, a protected area and part of Nanda Devi Biosphere Reserve in the western Himalaya. We analyzed community composition, population structure, regeneration patterns, and projected development of future compositional patterns. We sampled ten 10 x 10 m quadrat for tree species in each of 30 forest stands. We sampled shrubs in ten 5 x 5 m quadrat, and herbs in twenty 1 x 1 m quadrat within each forest stand. We recorded 248 plant species from 8 forest communities. Broadly the demographic profiles at study sites exhibited progressive structures suggesting long term persistence of the communities/species. Density--diameter distribution revealed greater proportions of seedlings and a significant decline （P 〈 0.05） in the proportion of trees in older age/size classes. Of the 23 recorded tree species, 13.0 % showed good, 52.2 % fair, 26.1% poor and 8.7 % no regeneration. Differences in regeneration by species are indicative of future foreststructure and dynamics. Assessment of changes in structure of forest types provides baseline data for development of priorities for conservation of other representative land- scapes in the reserve as well as in the Himalaya.
文摘Lead-free x(0.50(Ba_(0.7)Ca_(0.3)TiO_(3)-0.50Ba(Zr_(0.2)Ti_(0.8)O_(3)-(1-x)PVDF ceramic–polymer nanocomposites with x=0.025,0.05,0.10,0.15,0.20,0.25 were prepared using melt-mixing technique.The distribution of nanoceramic filler particles(0.50(Ba_(0.7)Ca_(0.3)TiO_(3)-0.50Ba(Zr_(0.2)Ti_(0.8)O_(3)in the PVDF matrix were examined using scanning electron microscope.Impedance analysis indicated the negative temperature coefficient of resistance character of all the test specimens.Filler concentrationdependent piezoelectric coefficient(d33Þdata followed exponential growth types of variation.The data for ac conductivity were found to obey Jonscher’s power law.The correlated barrier hopping(CBH)model was found to explain the mechanism of charge transport occurring in the system.The low value of loss tangent(-10^(-2))along with the high value of d_(33) foreshadowing the prospect of present nanocomposite is a better nonlead option for piezo-sensing/detection applications,especially in bio-medical area.
文摘Lead-free Ba(Fe_(1/2)Nb_(1/2))O_(3)/PVDF O_(3) composites were fabricated using melt.mixing technique.X-ray diffraction,scanning electron microscopy,dielectric,impedance,ac conductivity,magnetic force microscopy(MFM)and vibrating sample magne-tometer studies were undertaken to characterize the samples.Average crstallite size of the Ba(Fe_(1/2)Nb_(1/2))O_(3) powder,estimated using Williamson-Hall approach,was found to be~42 nm.The fller particles of~0.5-1 pum were found to disperse in the polymer matrix of all the composites.Filler concentration dependent values of real and imaginary parts of complex permittivity showed increasing trend and were seen to follow Bruggeman and Furukawa equations.The data for ac conductivity exhibited negative temperature coeficient of resistance character of the test materials and were found to obey Jonscher's power law.The correlated barier hopping model was found to explain satisfactorily the mechanism of charge transport occurring in the system.MFM confirmed the presence of magnetic phases in the composites.Typical magnetization versus applied field curves indicated the possibility of magnetoelectric coupling in the system.Hence,the present composites have shown themselves as potential multi-functional candidate materials for use in high density data storage applications.
文摘Temperature dependent X-ray diffraction(XRD)and dielectric properties of perovskite Ba(Zr_(0.2)Ti_(0.8))O_(3) ceramic prepared using a standard solid-state reaction process is presented.Along with phase transitions at low temperature,a new phase transition at high temperature(873℃ at 20 Hz),diffusive in character has been found where the lattice structure changes from monoclinic(space group:P2=m) to hexagonal(space group:P6=mmm).This result places present ceramic in the list of potential candidate for intended high temperature applications.The AC conductivity data followed hopping type charge conduction and supports jump relaxation model.The experimental value of d_(33)=98 pC/N was found.The dependence of polarization and strain on electric field at room temperature suggested that lead-free Ba(Zr_(0.2)Ti_(0.8))O_(3) is a promising material for electrostrictive applications.
