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Author: search.filters.author.Sutapun, ManoonSubject: search.filters.subject.Lead-free piezoelectric ceramics

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    Phase transition and dielectric properties of lead free (K 0.5Na0.5)NbO3- Bi(Zn0.5Ti 0.5)O3 piezoelectric ceramics
    (2009-12-01)
    Sutapun, Manoon
    ;
    Vittayakorn, Naratip
    Lead-free piezoelectric ceramics of (1-x)(K0.5Na0.5) NbO3 - x(Bi(Zn0.5Ti0.5)O3; x = 0.00-0.30 were prepared via the two-stage mixed oxide fabrication technique. The crystal structure and ferroelectric phase transitions were studied by means of x-ray diffraction and thermal measurements. XRD results showed that a single-phase perovskite structurewas formed in the ceramics with x ≤ 0.25. For the ceramics with x = 0.30, a small amount of secondary phase Bi2Ti2O7 with a cubic structure was formed. The ceramics with a perovskite structure showed an orthorhombic phase at 0.00 ≤ x ≤ 0.010 and became rhombohedral at 0.010 < x ≤ 0.015 before transforming to a cubic phase at 0.015 < x ≤ 0.25. In addition, DSC results showed that the phase transition temperature of orthorhombic-tetragonal (TO-T) and tetragonal-cubic (TC) decreased when a small amount of BZT was added. The trend of enthalpy for orthorhombic → tetragonal phase transition and tetragonal → cubic phase were found to reduce with progressive increases in small amounts of BZT content. This behavior could originate from the more complex occupation of the A and B sites in an ABO3 perovskite structure. Copyright © Taylor & Francis Group, LLC.
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    Phase transitional behavior and dielectric properties of lead free (1-x)(K0.5Na0.5)NbO3-xBi (Zn0.5Ti0.5)O3 ceramics
    (2009-06-24)
    Sutapun, Manoon
    ;
    Huang, Chien Chih
    ;
    Cann, David P.
    ;
    Vittayakorn, Naratip
    Lead-free ceramics based on potassium sodium niobate [(K<inf>0.5</inf>Na<inf>0.5</inf>)NbO<inf>3</inf>; KNN]-bismuth zinc titanate [Bi(Zn<inf>0.5</inf>Ti<inf>0.5</inf>)O<inf>3</inf>; BZT] were prepared by the modified-conventional mixed oxide route with normal sintering. The crystal structure and ferroelectric phase transitions were studied by means of X-ray diffraction, thermal and dielectric measurements. The ceramics with perovskite structure were in orthorhombic phase at x ≤ 0.010. When reaching 0.01 < x ≤ 0.03, they became a rhombohedral perovskite structure; and with increasing BZT content, cubic within the studied composition range. The phase Bi<inf>2</inf>Ti<inf>2</inf>O<inf>7</inf> with cubic structure began to appear at x > 0.25 and became dominant while increasing the content of BZT. Furthermore, the phase transition temperature of orthorhombic-tetragonal (T<inf>O-T</inf>) and tetragonal-cubic (T<inf>C</inf>) decreased when a small amount of BZT was added. As the amount of BZT concentration increased, the structure became denser, and well developed grain morphology with almost no porosity was finally obtained. © 2008 Elsevier B.V. All rights reserved.