Effects of ZnO nanoparticulate addition on the properties of PMNT ceramics

This research was conducted in order to study the effect of ZnO nanoparticulate addition on the properties of 0.9 Pb(Mg_1/3Nb_2/3)O₃-0.1PbTiO₃ [PMNT] ceramics. The PMNT ceramics were prepared by a solid-state reaction. The ZnO nanoparticles were added into PMNT ceramics to form PMNT/xZnO (x = 0, 0.05, 0.1, 0.5, and 1.0 wt.%). The PMNT/xZnO ceramics were investigated in terms of phase, microstructure, and mechanical and electrical properties. It was found that the density and grain size of PMNT ceramics tended to increase with an increasing amount of ZnO content. Moreover, a transgranular fracture was observed for the samples containing ZnO, while pure PMNT ceramics showed only a intergranular fracture. An addition of only 0.05 wt.% of ZnO was also found to enhance the hardness and dielectric and ferroelectric properties of the PMNT ceramics.     

Grain growth behavior in bismuth titanate-based ceramics

Bismuth titanate and lanthanum-doped bismuth titanate ceramics were prepared from freeze-dried powders employing conventional solid state reaction and sintering procedures. The sintering process was carried out at 1150 °C from 4 up to 48 h. X-ray diffraction analysis showed that preferred orientation was reduced in bismuth titanate ceramic as sintering time increased while lanthanum-doped sample showed much less degree of preferred orientation and was independent of sintering time. Grain growth studies also showed that initial anisotropic grain growth rate was the main factor controlling the grain morphology, rendering the plate-shaped grain in both pure and lanthanum-doped bismuth titanate ceramics. Based on established grain growth law, pore-controlled diffusion could be the major mechanism determining the observed microstructure in these layered compounds.     

Structure-property relations of co-doped bismuth layer-structured Bi3.25La0.75(Ti1-xMox)3O12 ceramics

In this work, the fabrication and investigation of substituting higher-valence Mo⁶⁺ for Ti⁴⁺ ion on the B-site of La³⁺-doped Bi₄Ti₃O₁₂ [BLT] structure to form Bi_3.25La_0.75(Ti_1-x Mo _x )₃O₁₂ [BLTM] (when x = 0, 0.01, 0.03, 0.05 0.07, 0.09, and 0.10) ceramics were carried out. X-ray diffraction patterns of BLTM ceramics indicated an orthorhombic structure with lattice distortion, especially with a higher concentration of a MoO₃ dopant. Microstructural investigation showed that all ceramics composed mainly of plate-like grains. An increase in MoO₃ doping content increased the length and thickness of the grain but reduced the density of the ceramics. Electrical conductivity was found to decrease, while the dielectric constant increased with Mo⁶⁺ doping concentration. Ferroelectric properties were found to be improved with increasing MoO₃ content and were optimized at x = 0.1.     

Crystal structure and electrical properties of bismuth sodium titanate zirconate ceramics

Lead-free bismuth sodium titanate zirconate (Bi_0.5Na_0.5Ti_1-xZr_xO₃ where x = 0.20, 0.35, 0.40, 0.45, 0.60, and 0.80 mole fraction) [BNTZ] ceramics were successfully prepared using the conventional mixed-oxide method. The samples were sintered for 2 h at temperatures lower than 1,000°C. The density of the BNTZ samples was at least 95% of the theoretical values. The scanning electron microscopy micrographs showed that small grains were embedded between large grains, causing a relatively wide grain size distribution. The density and grain size increased with increasing Zr concentration. A peak shift in X-ray diffraction patterns as well as the disappearance of several hkl reflections indicated some significant crystal-structure changes in these materials. Preliminary crystal-structure analysis indicated the existence of phase transition from a rhombohedral to an orthorhombic structure. The dielectric and ferroelectric properties were also found to correlate well with the observed phase transition.     

Investigation of a new lead-free Bi<Subscript>0.5</Subscript>(Na<Subscript>0.40</Subscript>K<Subscript>0.10</Subscript>)TiO<Subscript>3</Subscript>-(Ba<Subscript>0.7</Subscript>Sr<Subscript>0.3</Subscript>)TiO<Subscript>3</Subscript> piezoelectric ceramic

Lead-free piezoelectric compositions of the (1-x)Bi_0.5(Na_0.40K_0.10)TiO₃-x(Ba_0.7Sr_0.3)TiO₃ system (when x = 0, 0.05, 0.10, 0.15, and 0.20) were fabricated using a solid-state mixed oxide method and sintered between 1,050°C and 1,175°C for 2 h. The effect of (Ba_0.7Sr_0.3)TiO₃ [BST] content on phase, microstructure, and electrical properties was investigated. The optimum sintering temperature was 1,125°C at which all compositions had densities of at least 98% of their theoretical values. X-ray diffraction patterns that showed tetragonality were increased with the increasing BST. Scanning electron micrographs showed a slight reduction of grain size when BST was added. The addition of BST was also found to improve the dielectric and piezoelectric properties of the BNKT ceramic. A large room-temperature dielectric constant, ε _r (1,609), and piezoelectric coefficient, d ₃₃ (214 pC/N), were obtained at an optimal composition of x = 0.10.     

Enhanced Dielectric and Ferroelectric Properties of Pb(Mg1/3Nb2/3)0.65Ti0.35O3 Ceramics by ZnO Modification

Phase formation, microstructures, dielectric, and ferroelectric properties of ZnO‐modified Pb(Mg_1/3Nb_2/3)_0.65Ti_0.35O₃ (PMNT/xZnO, where x = 0, 0.4, 2.0, 4.0, and 11.0 mol%) ceramics were studied. A coexistence of rhombohedral and tetragonal ferroelectric phases was observed at room temperature in all samples. The ceramics with the relative densities of 93%–95% were prepared. The modification by ZnO led to an increase in grain sizes of PMNT ceramics. The maximum dielectric constant of the pure PMNT ceramic was increased with x = 0.4–4.0 mol% ZnO doping, with the highest value being observed in the 2.0 mol% sample. Both the temperature at which the transition between rhombohedral and tetragonal ferroelectric phases took place (T_R‐T) and the Curie temperature of the ceramics tended to increase with increasing x. The ferroelectric properties were enhanced with increased remanent polarization and P(E) loop squareness in the compositions with x = 0.4–4.0 mol%. However, the ferroelectric properties were attenuated with x = 11.0 mol%.     

Metabolic profiling of Angelica acutiloba roots utilizing gas chromatography-time-of-flight-mass spectrometry for quality assessment based on cultivation area and cultivar via multivariate pattern recognition

Gas chromatography time-of-flight mass spectrometry was applied to elucidate the profiling of primary metabolites and to evaluate the differences between quality differences in Angelica acutiloba (or Yamato-toki) roots through the utilization of multivariate pattern recognition-principal component analysis (PCA). Twenty-two metabolites consisting of sugars, amino and organic acids were identified. PCA analysis successfully discriminated the good, the moderate and the bad quality Yamato-toki roots in accordance to their cultivation areas. The results signified two reducing sugars, fructose and glucose being the most accumulated in the bad quality, whereas higher quantity of phosphoric acid, proline, malic acid and citric acid were found in the good and the moderate quality toki roots. PCA was also effective in discriminating samples derive from different cultivars. Yamato-toki roots with the moderate quality were compared by means of PCA, and the results illustrated good discrimination which was influenced most by malic acid. Overall, this study demonstrated that metabolomics technique is accurate and efficient in determining the quality differences in Yamato-toki roots, and has a potential to be a superior and suitable method to assess the quality of this medicinal plant.     

Ferroelectric properties of Pb(Zr0.52Ti0.48)O3–Bi3.25La0.75Ti3O12 ceramics

The ceramic samples of compound (1 ? x)Pb(Zr_0.52Ti_0.48)O₃–xBi_3.25La_0.75Ti₃O₁₂ (when x = 0, 0.03, 0.05, 0.07, 0.10, 0.15 and 0.20) were prepared by a solid-state mixed oxide method. X-ray diffraction analysis showed that complete solid solutions occurred for all compositions. Perovskite phase with tetragonal crystal structure and corresponding lattice distortion was observed. Scanning electron micrographs of sample surfaces showed equiaxed grains for all compositions. Ferroelectric measurements revealed that the addition of small amount of BLT (x = 0.03) showed high remanent polarization (～33.5 μC cm^?2) and low coercive field (～2.74 kV mm^?1). Further increasing BLT content could maintain ferroelectric properties of PZT–BLT ceramics. Based on this study, ferroelectric properties of this PZT–BLT ceramic system can be improved for being further used in ferroelectric memory applications.     

Effects of Nb-doping on the micro-structure and dielectric properties of (Bi0.5Na0.5)TiO3 ceramics

Bismuth sodium titanate [(Bi_0.5Na_0.5)TiO₃ or BNT] ceramics incorporated with 0, 1, 5, 10, 15 and 20 mol% niobium were prepared by conventional solid state reaction method. The green bodies were sintered at 1050 °C for 2 h to obtain dense ceramics. The effects of substitution of niobium ion for titanium ion in BNT ceramics on micro-structure and dielectric properties were investigated. X-ray diffraction analysis showed the presence of a secondary phase when more than 5 mol% niobium was added. Within the solubility limit, Nb doping caused the grain size of BNTNb to be smaller than the undoped sample. The investigation of the dielectric properties showed that the transition temperature (T_c) was found to shift towards lower temperature as the content of Nb increased. In this research, the donor-type behavior and induced charged defects had significant influence on the electrical properties of Nb-doped BNT ceramics.