Pb_(x)Sr_(1-x)TiO_(3)(x=0.30,0.35,0.40,0.45,0.50 and 0.55)ceramics were fabricated by a solid-state reaction route.Xeray diffraction data at room temperature show PST samples shift from cubic to tetragonal phase with ...Pb_(x)Sr_(1-x)TiO_(3)(x=0.30,0.35,0.40,0.45,0.50 and 0.55)ceramics were fabricated by a solid-state reaction route.Xeray diffraction data at room temperature show PST samples shift from cubic to tetragonal phase with the increase of Pb^(2+) content.The microstructures were observed by scanning electron microscopy.Dielectric measurement was employed to investigate the ferroelectriceparaelectric phase transition behavior.Temperature dependent polarizationeelectric field hysteresis loops were conducted to study the electrocaloric effect(ECE)of the ferroelectric ceramics by indirect methods over a wide temperature range.Direct measurement of temperature change(DT)at room temperature for all samples can achieve 0.79e1.86 K.What's more,a giant ECE(△T=2.05 K,EC strength(△T/△E)=0.51×10^(-6) K m/V,under 40 kV/cm)was obtained in the sample of x=0.35 near phase transition temperature.Our results suggest that the ceramics are promising cooling materials with excellent EC properties for energy related applications.展开更多
The study aims to investigate the structural and dielectric properties of perovskite La_(1-x)Sr_(x)FeO_(3)(x=0.1,0.2,0.3,and 0.4)synthesized by solgel and sintering methods.X-ray diffraction(XRD),transmission electron...The study aims to investigate the structural and dielectric properties of perovskite La_(1-x)Sr_(x)FeO_(3)(x=0.1,0.2,0.3,and 0.4)synthesized by solgel and sintering methods.X-ray diffraction(XRD),transmission electron microscopy(TEM),and LCR-Meter were used to identify the phase,crystallography parameters,morphology,particle size,and electrical behavior of the synthesized perovskite materials.The samples showed a single-phase orthorhombic crystal structure with Pbnm space group.Sr-substitution induced the volume unit cell and crystallite size to decrease.The synthesized nanoparticles were uniform and homogeneous with the particle size less than 200 nm.Impedance spectroscopy(IS)was used to explain the electrical behavior as a function of frequency(100 Hz to 1 MHz)at various temperatures(300–373 K).The presence of small polarons as charge carriers within the grain and grain boundary were elucidated from the electrical conductivity experiments.Sr-substitution caused the dielectric constant and electronic conductivity to increase with the highest values obtained from La_(1-x)Sr_(x)FeO_(3)(x=0.4).展开更多
The powders of lead-free material namely(nonhazardous)barium strontium titanate(BST)with different stoichiometric compo-sitions have been synthesized by the sol-gel method.Ba_(1−x)Sr_(x)TiO_(3)(BST)materials possess t...The powders of lead-free material namely(nonhazardous)barium strontium titanate(BST)with different stoichiometric compo-sitions have been synthesized by the sol-gel method.Ba_(1−x)Sr_(x)TiO_(3)(BST)materials possess the properties of both ferroelectric and dielectric materials.These materials have spontaneous polarization that can be reversed by an applied electric field and they remain polarized even when the applied external electric field is removed.Synthesized samples have been subjected to structural,morphological,and dielectric characterizations.In this study,BST nanopowders with different substitutions of x(where x=0.2,0.3,0.4,0.5,and 0.6)were prepared by the sol-gel method,which is an easy method with low power consumption and low tem-perature requirement and produces higher yield.Nanopowders had average particle sizes of 12-24 nm and particles sizes after sintering at 1000°C for 3 h were 197,267,79.80,63.09,and 63 nm.All resulting pellets had a polycrystalline structure.Crystal structure,space group,morphological characterization,and particle size were determined from the structural analysis using X-ray powder diffraction(XRD),energy-dispersive X-ray spectroscopy(EDX),and scanning electron microscopy(SEM).The dielec-tric measurements were made for BST pellets under different frequencies(1-200 kHz)from room temperature to 250℃.The dielectric constants for the bulk were 743,1566,1091,766,and 626 for x=0.2,0.3,0.4,0.5,and 0.6,respectively.From dielectric measurements,samples with x=0.2 and 0.3 had the Curie temperatures of 70℃ and 28.5℃,respectively,and remained intact below 0℃.The sample with x=0.3 had a good dielectric measurement and moderate dissipation factor;it may be used in capac-itance application as energy stores.展开更多
基金the National Natural Science Foundation of China(Grant Nos.11574057 and 51604087)the Guangdong Provincial Natural Science Foundation of China(Grant No.2016A030313718)the Science and Technology Program of Guangdong Province of China(Grant Nos.2016A010104018,and 2017A010104022).
文摘Pb_(x)Sr_(1-x)TiO_(3)(x=0.30,0.35,0.40,0.45,0.50 and 0.55)ceramics were fabricated by a solid-state reaction route.Xeray diffraction data at room temperature show PST samples shift from cubic to tetragonal phase with the increase of Pb^(2+) content.The microstructures were observed by scanning electron microscopy.Dielectric measurement was employed to investigate the ferroelectriceparaelectric phase transition behavior.Temperature dependent polarizationeelectric field hysteresis loops were conducted to study the electrocaloric effect(ECE)of the ferroelectric ceramics by indirect methods over a wide temperature range.Direct measurement of temperature change(DT)at room temperature for all samples can achieve 0.79e1.86 K.What's more,a giant ECE(△T=2.05 K,EC strength(△T/△E)=0.51×10^(-6) K m/V,under 40 kV/cm)was obtained in the sample of x=0.35 near phase transition temperature.Our results suggest that the ceramics are promising cooling materials with excellent EC properties for energy related applications.
基金Ministry of TechnologyResearch and Higher Education of Republic of Indonesiaunder KLN Grant No. 537/UN2.R3.1/HKP05.00/2018.
文摘The study aims to investigate the structural and dielectric properties of perovskite La_(1-x)Sr_(x)FeO_(3)(x=0.1,0.2,0.3,and 0.4)synthesized by solgel and sintering methods.X-ray diffraction(XRD),transmission electron microscopy(TEM),and LCR-Meter were used to identify the phase,crystallography parameters,morphology,particle size,and electrical behavior of the synthesized perovskite materials.The samples showed a single-phase orthorhombic crystal structure with Pbnm space group.Sr-substitution induced the volume unit cell and crystallite size to decrease.The synthesized nanoparticles were uniform and homogeneous with the particle size less than 200 nm.Impedance spectroscopy(IS)was used to explain the electrical behavior as a function of frequency(100 Hz to 1 MHz)at various temperatures(300–373 K).The presence of small polarons as charge carriers within the grain and grain boundary were elucidated from the electrical conductivity experiments.Sr-substitution caused the dielectric constant and electronic conductivity to increase with the highest values obtained from La_(1-x)Sr_(x)FeO_(3)(x=0.4).
文摘The powders of lead-free material namely(nonhazardous)barium strontium titanate(BST)with different stoichiometric compo-sitions have been synthesized by the sol-gel method.Ba_(1−x)Sr_(x)TiO_(3)(BST)materials possess the properties of both ferroelectric and dielectric materials.These materials have spontaneous polarization that can be reversed by an applied electric field and they remain polarized even when the applied external electric field is removed.Synthesized samples have been subjected to structural,morphological,and dielectric characterizations.In this study,BST nanopowders with different substitutions of x(where x=0.2,0.3,0.4,0.5,and 0.6)were prepared by the sol-gel method,which is an easy method with low power consumption and low tem-perature requirement and produces higher yield.Nanopowders had average particle sizes of 12-24 nm and particles sizes after sintering at 1000°C for 3 h were 197,267,79.80,63.09,and 63 nm.All resulting pellets had a polycrystalline structure.Crystal structure,space group,morphological characterization,and particle size were determined from the structural analysis using X-ray powder diffraction(XRD),energy-dispersive X-ray spectroscopy(EDX),and scanning electron microscopy(SEM).The dielec-tric measurements were made for BST pellets under different frequencies(1-200 kHz)from room temperature to 250℃.The dielectric constants for the bulk were 743,1566,1091,766,and 626 for x=0.2,0.3,0.4,0.5,and 0.6,respectively.From dielectric measurements,samples with x=0.2 and 0.3 had the Curie temperatures of 70℃ and 28.5℃,respectively,and remained intact below 0℃.The sample with x=0.3 had a good dielectric measurement and moderate dissipation factor;it may be used in capac-itance application as energy stores.
