Potassium bismuth titanate nanosized powders were prepared by the hydrothermal method using Ti(C_4H_9O)_4 and Bi(NO_3)_3·5H_2O as raw materials in alkaline solution.The phase composition,particle size and morphol...Potassium bismuth titanate nanosized powders were prepared by the hydrothermal method using Ti(C_4H_9O)_4 and Bi(NO_3)_3·5H_2O as raw materials in alkaline solution.The phase composition,particle size and morphology of the powders were studied by XRD and TEM analysis.The results showed that the powders were well crystallized and dispersed.The crystal phase of the powders was K_(0.5)Bi_(0.5)TiO_3 with the grain size of about 50 nm～100 nm.Hydrothermal temperature and alkaline concentrations had great effects on the phase composition and morphology of the resultant powders.Pure K_(0.5)Bi_(0.5)TiO_3 powders could be synthesized at 170℃～180℃with KOH concentration of 8 mol/L～12 mol/L.展开更多
Solid solutions of the lead-free ferroelectric oxides Bi_(0.5)Na_(0.5)TiO_(3)(BNT)and Bi_(0.5)Na_(0.5)TiO_(3)(BKT),represented as(1-x)BNT-xBKT,are studied for very close compositions in the range0≤x≤0.36 to understa...Solid solutions of the lead-free ferroelectric oxides Bi_(0.5)Na_(0.5)TiO_(3)(BNT)and Bi_(0.5)Na_(0.5)TiO_(3)(BKT),represented as(1-x)BNT-xBKT,are studied for very close compositions in the range0≤x≤0.36 to understand the correlation between the structure and the properties.Compositions are varied in steps of △x=0.02 in the range0≤x≤0.1 and0.2≤x≤0.36 and△x=0.01 in the range 0.1≤x≤0.2,to precisely locate the structural transition as well as the morphotropic phase boundary(MPB)region and the compositional region of best performance.Rietveld refinement analysis of the powder X-ray diffraction patterns showed monoclinic phase up to x=0.17 and a mixture of monoclinic and tetragonal phases for x>0.17.Similarly,the density and the dielectric constant showed linear variation up to x=0.17 and a large increase above this composition,showing maximum values in the compositional range 0.22≤x≤0.26,corresponding to the MPB region.Microstructural features also showed corresponding changes,indicating close relationship between the structure,microstructure and properties of the different compositions.展开更多
Single crystals of x(Bi,K)TiO_(3)-(1-x)(Bi,Na)TiO_(3)(0.11≤x≤0.47) were grown by a flux method and their polarization and piezoelectric properties were investigated along h100i cubic at 25℃.Rietveld analysis of pow...Single crystals of x(Bi,K)TiO_(3)-(1-x)(Bi,Na)TiO_(3)(0.11≤x≤0.47) were grown by a flux method and their polarization and piezoelectric properties were investigated along h100i cubic at 25℃.Rietveld analysis of powder X-ray diffraction data provides a tentative phase diagram in this system.rhombohedral R3c for x≤0.22,pseudocubic for 0.22<x<0.3 and tetragonal P4mm for 0.3≤x.Piezoelectric strain properties show that the crystals(x=0.38)exhibited an extremely large piezoelectric strain constant of 637 pm/V.展开更多
文摘Potassium bismuth titanate nanosized powders were prepared by the hydrothermal method using Ti(C_4H_9O)_4 and Bi(NO_3)_3·5H_2O as raw materials in alkaline solution.The phase composition,particle size and morphology of the powders were studied by XRD and TEM analysis.The results showed that the powders were well crystallized and dispersed.The crystal phase of the powders was K_(0.5)Bi_(0.5)TiO_3 with the grain size of about 50 nm～100 nm.Hydrothermal temperature and alkaline concentrations had great effects on the phase composition and morphology of the resultant powders.Pure K_(0.5)Bi_(0.5)TiO_3 powders could be synthesized at 170℃～180℃with KOH concentration of 8 mol/L～12 mol/L.
文摘Solid solutions of the lead-free ferroelectric oxides Bi_(0.5)Na_(0.5)TiO_(3)(BNT)and Bi_(0.5)Na_(0.5)TiO_(3)(BKT),represented as(1-x)BNT-xBKT,are studied for very close compositions in the range0≤x≤0.36 to understand the correlation between the structure and the properties.Compositions are varied in steps of △x=0.02 in the range0≤x≤0.1 and0.2≤x≤0.36 and△x=0.01 in the range 0.1≤x≤0.2,to precisely locate the structural transition as well as the morphotropic phase boundary(MPB)region and the compositional region of best performance.Rietveld refinement analysis of the powder X-ray diffraction patterns showed monoclinic phase up to x=0.17 and a mixture of monoclinic and tetragonal phases for x>0.17.Similarly,the density and the dielectric constant showed linear variation up to x=0.17 and a large increase above this composition,showing maximum values in the compositional range 0.22≤x≤0.26,corresponding to the MPB region.Microstructural features also showed corresponding changes,indicating close relationship between the structure,microstructure and properties of the different compositions.
基金This study was partly supported by Grant-in-Aid for Scientific Research on Priority Areas"Novel States of Matter Induced by Frustration"(19052002)the Fundamental R&D Program for Core Technology of Materials funded by the Ministry of Knowledge Economy,Republic of Korea。
文摘Single crystals of x(Bi,K)TiO_(3)-(1-x)(Bi,Na)TiO_(3)(0.11≤x≤0.47) were grown by a flux method and their polarization and piezoelectric properties were investigated along h100i cubic at 25℃.Rietveld analysis of powder X-ray diffraction data provides a tentative phase diagram in this system.rhombohedral R3c for x≤0.22,pseudocubic for 0.22<x<0.3 and tetragonal P4mm for 0.3≤x.Piezoelectric strain properties show that the crystals(x=0.38)exhibited an extremely large piezoelectric strain constant of 637 pm/V.
