We hereby report the room-temperature structural and optical characterization of RECr_(0.85)Mn_(0.15)O_(3)(RECMO,RE=Ho,Gd and Pr)compounds synthesized by the auto-combustion sol-gel route.Their low temperature dielect...We hereby report the room-temperature structural and optical characterization of RECr_(0.85)Mn_(0.15)O_(3)(RECMO,RE=Ho,Gd and Pr)compounds synthesized by the auto-combustion sol-gel route.Their low temperature dielectric properties are also presented.The RECMO compounds crystallize in an orthorhombic Pbnm symmetry with an average grain size range of 51-80 nm.Structural analysis reveals an increase in the structural distortion compared to that of the undoped bulk compounds.Optical measurements exhibit a significant reduction in bandgap values for RECMO nanoparticles when compared with their undoped bulk compounds.Further,from the absorbance measurements various optical parameters such as skin depth,extinction coefficient,refractive index and optical conductivity were also calculated.The dielectric analysis confirms the lower values of the dielectric permittivity and dielectric loss than those of their corresponding bulk compounds.AC conductivity versus frequency and temperature data are fitted according to the Jonscher's power law and Arrhenius law,respectively.The small polaron hopping is responsible for the electric conduction in these compounds.The tunability of the optical and dielectric properties as a result of substitution and particle size reduction makes these materials useful for various potential applications in photocatalysis,optoelectronics and low permittivity dielectrics.展开更多
In the last few years,there has been tremendous effort to develop lead-free ferroelectric ceramics with high piezoelectric properties by various doping and alloying routes.Several material systems have been explored,h...In the last few years,there has been tremendous effort to develop lead-free ferroelectric ceramics with high piezoelectric properties by various doping and alloying routes.Several material systems have been explored,however,no prominent alternative to the versatile lead zirconate titanate(PZT)system has been found yet.Despite the achieved improvement in piezoelectric properties,there are problems in the synthesis,processing and poling of the sintered ceramics.Various processing techniques including microwave,hydrothermal,solgel,Pechini and spark plasma sintering have been used to overcome the drawbacks related to synthesis issues.In this paper,an attempt is made to review recent developments on lead-free piezo materials emphasizing their preparation,structureproperty relations,and consequent physical properties.In this context,both compositional and structural engineering approaches to achieve acceptable piezoelectric properties in lead-free materials are discussed.Piezoelectric properties of the most promising lead-free compositions/families including titanates,alkaline niobates and bismuth perovskites and their solid solutions,along with non-perovskites such as bismuth layer-structured ferroelectrics are reviewed in detail.A brief coverage of the recent developments in the area of piezoelectric energy harvesting is also encompassed.展开更多
基金Project supported by the Science and Engineering Research Board(SERB)New Delhi,India(ECR/2017/002681)Inter University Accelerator Centre,New Delhi,India(UFR-62317)。
文摘We hereby report the room-temperature structural and optical characterization of RECr_(0.85)Mn_(0.15)O_(3)(RECMO,RE=Ho,Gd and Pr)compounds synthesized by the auto-combustion sol-gel route.Their low temperature dielectric properties are also presented.The RECMO compounds crystallize in an orthorhombic Pbnm symmetry with an average grain size range of 51-80 nm.Structural analysis reveals an increase in the structural distortion compared to that of the undoped bulk compounds.Optical measurements exhibit a significant reduction in bandgap values for RECMO nanoparticles when compared with their undoped bulk compounds.Further,from the absorbance measurements various optical parameters such as skin depth,extinction coefficient,refractive index and optical conductivity were also calculated.The dielectric analysis confirms the lower values of the dielectric permittivity and dielectric loss than those of their corresponding bulk compounds.AC conductivity versus frequency and temperature data are fitted according to the Jonscher's power law and Arrhenius law,respectively.The small polaron hopping is responsible for the electric conduction in these compounds.The tunability of the optical and dielectric properties as a result of substitution and particle size reduction makes these materials useful for various potential applications in photocatalysis,optoelectronics and low permittivity dielectrics.
基金The authors I.C.and N.P.would like to thank the Portuguese foundation FCT through their grants SFRH/BPD/81032/2011 and SFRH/BPD/71289/2010,respectivelyFinancial support from FCT through the projects PTDC/FIS/108025/2008 and PTDC/CTM-CER/115085/2009 is also acknowledged.
文摘In the last few years,there has been tremendous effort to develop lead-free ferroelectric ceramics with high piezoelectric properties by various doping and alloying routes.Several material systems have been explored,however,no prominent alternative to the versatile lead zirconate titanate(PZT)system has been found yet.Despite the achieved improvement in piezoelectric properties,there are problems in the synthesis,processing and poling of the sintered ceramics.Various processing techniques including microwave,hydrothermal,solgel,Pechini and spark plasma sintering have been used to overcome the drawbacks related to synthesis issues.In this paper,an attempt is made to review recent developments on lead-free piezo materials emphasizing their preparation,structureproperty relations,and consequent physical properties.In this context,both compositional and structural engineering approaches to achieve acceptable piezoelectric properties in lead-free materials are discussed.Piezoelectric properties of the most promising lead-free compositions/families including titanates,alkaline niobates and bismuth perovskites and their solid solutions,along with non-perovskites such as bismuth layer-structured ferroelectrics are reviewed in detail.A brief coverage of the recent developments in the area of piezoelectric energy harvesting is also encompassed.
