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Influence of fabrication processing on perovskite phase formation of KNN-BZT
(2008-01-01)
Sutapun, M.
;
Muanghlua, R.
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Huang, C. C.
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Cann, D. P.
;
Vittayakorn, W. C.
The binary system of (1-x)(K<inf>1/2</inf>Na<inf>1/2</inf>)NbO <inf>3</inf>-xBi(Zni/2Ti<inf>1/2</inf>)O<inf>3</inf>; 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. © 2008 Trans Tech Publications, Switzerland.
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Preparation and ferroelectric properties of pyrochlore-free Pb(Ni 1/3Nb2/3)O3-based solid solutions
(2007-03-01)
Vittayakorn, N.
;
Cann, D. P.
Polycrystalline ceramics of the perovskite solid solution 0.5Pb(Ni <inf>1/3</inf>Nb<inf>2/3</inf>)O<inf>3</inf>-(0.5-x)-Pb(Zn<inf>1/3</inf>Nb <inf>2/3</inf>)O<inf>3</inf>-xPb(Zr<inf>1/2</inf>Ti<inf>1/2</inf>)O <inf>3</inf>; x=0.0-0.5 (PNN-PZN-PZT) were synthesized by a modified columbite method. Highly dense ceramics lacking parasitic pyrochlore phases were prepared at a calcination temperature of 950 °C by using a double-crucible configuration, excess PbO (2 mol∈%), and a fast heating/cooling rate (20 °C/min). The ceramics were characterized by a variety of techniques including X-ray diffraction, ferroelectric hysteresis loop measurements, field-induced longitudinal strain measurements, and electron microscopy. It was observed that the remanent polarization exhibited a significant increase with increasing x. In addition, the squareness of the hysteresis loop increased quasi-linearly as the molar fraction of PZT increased. The maximum spontaneous polarization and remanent polarization for the x=0.5 composition were 31.9 μC/cm<sup>2</sup> and 25.2 μC/cm<sup>2</sup>, respectively. Moreover, the data were analyzed to show the evolution of the micro-domain state as a function of the molar fraction of PZT. © Springer-Verlag 2007.
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Piezoelectric properties of (1 - x)Pb(Zr1/2Ti1/2)O3-xPb(Zn1/3Nb2/3)O3 ceramics prepared by the columbite-(wolframite) precursor method
(2006-06-01)
Vittayakorn, N.
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Puchmark, C.
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Rujijanagul, G.
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Tan, X.
;
Cann, D. P.
Solid solutions of the perovskite structure, (1 - x)Pb(Zr<inf>1/2</inf>Ti<inf>1/2</inf>)O<inf>3</inf>-xPb(Zn<inf>1/3</inf>Nb<inf>2/3</inf>)O<inf>3</inf> with x = 0.1-0.5, were synthesized via the columbite-(wolframite) precursor method. The phase development of calcined powder precursors was analyzed by X-ray diffraction. Phase-pure perovskite of PZN-PZT ceramics was obtained over a wide compositional range. The microstructure and piezoelectric properties were characterrized by means of scanning electron microscopy (SEM), d<inf>33</inf> measurements and impedance analysis. It has been found that ultra-high piezoelectric properties were observed in compositions close to a morphotropic phase boundary (MPB). The maximum value of d<inf>33</inf> (690 pC/N) and the highest k<inf>p</inf> (0.7) were recorded for the composition x = 0.3 located at the boundary between tetragonal and rhombohedral ferroelectric phases. Furthermore, large values of d<inf>33</inf> (600 pC/N) and k<inf>p</inf> (0.67) were observed at a compositions of x = 0.5, which is the boundary between two ferroelectric rhombohedral phases. © 2005 Elsevier B.V. All rights reserved.
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Dielectric properties and morphotropic phase boundaries in the xPb(Zn 1/3Nb2/3)O3-(1-x)Pb(Zr0.5Ti 0.5O3 pseudo-binary system
(2006-03-01)
Vittayakorn, N.
;
Rujijanagul, G.
;
Tan, X.
;
He, H.
;
Marquardt, M. A.
Ceramics in the xPb(Zn<inf>1/3</inf>Nb<inf>2/3</inf>)O <inf>3</inf>-(1-x) Pb(Zr<inf>0.5</inf>Ti<inf>0.5</inf>)O<inf>3</inf> [xPZN-(1-x)PZT] solid solution system are expected to display excellent dielectric, piezoelectric, and ferroelectric properties in compositions close to the morphotropic phase boundary (MPB). The dielectric behavior of ceramics with x = 0.1-0.6 has been characterized in order to identify the MPB compositions in this system. Combined with X-ray diffraction results, ferroelectric hysteresis measurements, and Raman reflectivity analysis, it was consistently shown that an MPB exists between x = 0.2 and x = 0.3 in this binary system. When x ≤ 0.2, the tetragonal phase dominates at ambient temperatures. In the range of x ≥ 0.3, the rhombohedral phase dominates. For this rhombohedral phase, electrical measurements reveal a profound frequency dispersion in the dielectric response when x ≥ 0.6, suggesting a transition from normal ferroelectric to relaxor ferroelectric between 0.5 ≥ x ≤ 0.6. Excellent piezoelectric properties were found in 0.3PZN-0.7PZT, the composition closest to the MPB with a rhombohedral structure. The results are summarized in a PZN-PZT binary phase diagram. © Springer Science + Business Media, Inc. 2006.

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