Advanced Materials Research Vols. 55-57

Abstract: Barium zirconate fine powders of pure cubic phase were readily prepared from the reactions between BaCl22H2O and ZrOCl28H2O under ammonothermal conditions at a very low temperature of 130oC as the lowest. KOH concentration was important in determining phase formation and particle morphology. Reaction temperature and time showed influences on the evolution of particle morphology and aggregation formation, respectively. Sizes of the primary particles critically depended on the BaII:ZrIV mole ratio. Phase formation mechanism is suggested.

Abstract: The structure and electrical properties of Al2O3-doped 0.2Pb(Zn1/3Nb2/3)O3-0.8Pb(Zr1/2Ti1/2)O3 ceramic, which is the morphotropic phase boundary composition of the PZN-PZT system, were investigated. The addition of Al2O3 content transformed the crystal structure rom coexisting with rhombohedral to purely tetragonal structure. Furthermore, addition of Al2O3 decreased r, d33 and kp, but increased Curie temperature and enhanced the mechanical quality factor. inally, the P–E and s-E loops demonstrated decreased Pr, Ec and strain level with addition of Al2O3

Abstract: In this study, the influence of Mn addition on phase formation, microstructure and electrical properties of Ba(Ti1-xMnx)O3 where x = 0.01 to 0.2 was investigated. The XRD patterns showed that the crystal structure of Ba(Ti1-xMnx)O3 at room temperature changed from tetragonal to hexagonal as Mn concentration increased, which also caused the room temperature dielectric constant decrease from 1143 to 47. The microstructure of Ba(Ti1-xMnx)O3 ceramics at low concentration revealed a bimodal microstructure. As the x value increased, the well grown grains decreased with the extent of fine-grained increased. Ferroelectric hysteresis (P-E) loop was not clearly observed as Mn concentration increased because of the formation of paraelectric hexagonal phase

Abstract: Poly (vinylidene fluoride), Piezoelectric, Dielectric constant, Microporous PVDF films, Bubble shapes.

Abstract: This research proposed a novel nano barium strontium titanate (BST) powder- polybenzoxazine composite as a new dielectric material. In this work, the dielectric properties of a surface-treated BST powder-polybenzoxazine composite were studied. The surface of the BST powders were modified by using three different chemicals: 3-aminopropyl-trimethoxysilane, benzoxazine monomer and phthalocyanine. The distribution of the BST powders in the polybenzoxazine matrix was observed by SEM. The dielectric constants of the composites with a function of frequency (1 kHz–10 MHz) were investigated. It was found that the composites with modified BST powders showed good distribution in the polybenzoxazine matrix, and the dielectric constants were also much enhanced than those with untreated BST powders. In comparisons among the three modification methods, the composite with the silane coupling modified BST powder showed significantly in dielectric constant improvement while the composite with the benzoxazine and phthalocyanine modified BST powders displayed lower dielectric loss due to the modified powder dispersed well in the polybenzoxazine matrix.

Abstract: A combination between piezoelectric (Pb(Zr1/2Ti1/2)O3; PZT) and relaxor ferroelectric (Pb(Co1/3Nb2/3)O3; PCN) materials with a formula of 0.8Pb(Zr1/2Ti1/2)O3 - 0.2Pb(Co1/3Nb2/3)O3 has been prepared with solid-state reaction (the columbite-wolframite precursor method). This specific composition was selected for investigation because it is close to a morphotropic phase boundary (MPB) between the tetragonal and pseudo cubic phases. The phase formation behavior and microstructure were studied using x-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The dielectric properties of the compound were measured and discussed. The ceramics were also heat-treated at 800 oC. The results showed that the dielectric properties of the compound depended significantly on the heat treatment conditions. Most importantly, this study showed that the addition of PCN can improve the dielectric characteristics in PZT ceramics.

Abstract: The binary system of (1-x)(K1/2Na1/2)NbO3–xBi(Zn1/2Ti1/2)O3; x = 0.0-0.30 ceramics was fabricated by conventionally mixed oxide and two-stage mixed oxide methods. Phase development of calcined powders and the crystal structure of sintered ceramics were analyzed by X-ray diffraction (XRD). The microstructure analyses were undertaken by scanning electron microscopy (SEM). In the conventional method, the perovskite phases were obtained for compositions containing only 10 mol % KNN. For compositions above this amount, a complex mixture of phases was observed. However, the complete solid solution of perovskite phase, prepared by two−stage mixed oxide, was retained up to 20 mole % BZT content. The experiments in this study suggest that the two-stage mixed oxide method helps to stabilize the perovskite phase better, when compared with the conventional method.

Abstract: The solid solution between the antiferroelectric, PbZrO3 (PZ), and relaxor ferroelectric, Pb(Ni1/3Nb2/3)O3 (PNN), was synthesized by the columbite method. The phase structure and phase transition of Pb(Zr1-x(Ni1/3Nb2/3)xO3 (PZNN), where x = 0.0 ≤ x ≤ 0.50, were investigated. The samples were kept at the calcination temperature of 900°C for 4 h and at the sintering temperature of 1,150°C for 2 h. Phase formation and phase transition of PZNN were investigated by x-ray diffraction (XRD) and thermal analysis, respectively. It was found that the structure of sintered pellets is orthorhombic for 0.0 ≤ x ≤ 0.10, rhombohedral for 0.20 ≤ x ≤ 0.30 and pseudo-cubic for x = 0.5. DSC measurement shows that in the antiferroelectric (AFE) phase – ferroelectric (FE) phase and FE to paraelectric (PE) phase; phase transformation temperatures decrease with increasing PNN concentration. The AFE–FE phase transformation was detected for compositions 0.00 £ x £ 0.08.

Abstract: The phase transition behavior of the (1–x) PbZrO3-xPb(Co1/3Nb2/3)O3 (PZCN) solid solution system (0 ≤ x ≤ 0.30) has been investigated by X-ray diffraction and DSC. In the solid solution, for x ≤ 0.20, the transition shows a first-order phase transition behavior and its antiferroelectric (AFE) crystal structure is orthorhombic. The transition temperature gradually decreases with increased Co2+/Nb5+ concentration. On the composition range 0.20 ≤ x ≤ 0.30, a typical relaxor-like behavior is displayed. The low temperature crystal structure is pseudo-cubic in this composition range. With these data, the ferroelectric phase diagram between PZ and PCoN has been established.