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Author: search.filters.author.Muanghlua, RangsonSubject: search.filters.subject.phase transition

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    Phase transition, dielectric and piezoelectric properties of lead-free piezoelectric (K1/2Na1/2)NbO3 - Bi(Zn2/3Nb1/3)O3 ceramics
    (2016-01-02)
    Sutapun, Manoon
    ;
    Muanghlua, Rangson
    ;
    Vittayakorn, Naratip
    The lead-free piezoelectric ceramics on the binary system of (1-x)(K<inf>1/2</inf>Na<inf>1/2</inf>)NbO<inf>3</inf>-xBi(Zn<inf>2/3</inf>Nb<inf>1/3</inf>)O<inf>3</inf> [(1-x)KNN-xBZnN]; x = 0.01-0.10 were fabricated by the solid state reaction method. The structure and phase transition were determined by X-ray diffraction.The results of XRD patterns suggested that Bi(Zn<inf>2/3</inf>Nb<inf>1/3</inf>)O<inf>3</inf> completely diffuse into the (K<inf>1/2</inf>Na<inf>1/2</inf>)NbO<inf>3</inf> lattices to form a solid solution. The crystal structure was in an orthorhombic phase for x ≤ 0.01. When reaching 0.01 < x ≤ 0.07, crystal structure became a rhombohedral phase and transformed to a pseudo-cubic structure for x > 0.07. The dielectric data shows that the amount of Bi(Zn<inf>2/3</inf>Nb<inf>1/3</inf>)O<inf>3</inf> added in the (K<inf>1/2</inf>Na<inf>1/2</inf>)NbO<inf>3</inf> decreases the ferroelectric - paraelectric transition temperature progressively. Furthermore, optimum piezoelectric and ferroelectric properties were observed at the composition, x = 0.01: effective piezoelectric coefficients (d<inf>33</inf>) = 498 pm/V, remanent polarization (P<inf>r</inf>) = 23.3 μC/cm<sup>2</sup>, coercive field (E<inf>c</inf>) = 14 kV/cm, maximum strain (Sma<inf>x</inf>) = 0.3% and Curie temperature (T<inf>C</inf>) = 380°C. The results of this study show that KNN with a small amount of Bi(Zn<inf>2/3</inf>Nb<inf>1/3</inf>)O<inf>3</inf> (x = 0.01) can be one of lead-free piezoelectric ceramic candidate.
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    Dielectric, ferroelectric and piezoelectric properties of the lead free 0.9BaTiO3-(0.1- x)Bi0.5Na0.5TiO3- x Bi(Mg0.5Ti0.5)O3 solid solution
    (2016-01-02)
    Mayamae, Jitkasem
    ;
    Sukkha, Usa
    ;
    Niemchareon, Surasak
    ;
    Muanghlua, Rangson
    ;
    Vittayakorn, Naratip
    Solid solution of 0.9BaTiO<inf>3</inf>-(0.1-x)Bi<inf>0.5</inf>Na<inf>0.5</inf>TiO<inf>3</inf>-xBi(Mg<inf>0.5</inf>Ti<inf>0.5</inf>)O<inf>3</inf> (BT-BNT-xBMT) system, where x = 0.00, 0.02, 0.04, 0.06, 0.08, 0.10, was synthesized by the solid state reaction. Dense BT-BNT-xBMT ceramics were obtained by sintering at 1,150-1,250C for 4 h. The effect of BMT on crystal structure and electrical property of BT-BNT ceramics was investigated as a function of composition, x, using X-ray diffraction, dielectric spectroscopy, hysteresis and strain measurements. The crystal structure of solid solution BT-BNT-xBMT, where x = 0.00-0.10, successively transforms from tetragonal to pseudocubic symmetry, with increased BMT concentration. Temperature dependence of dielectric constant (ε<inf>r</inf>) and dielectric loss (tanδ) for BT-BNT-xBMT at various frequencies showed that phase transition of ceramics changed from ferroelectric to relaxor-like behavior as BMT content increased. Furthermore, remanent polarization (P<inf>r</inf>), coercive field (E<inf>c</inf>) and the normalized strain (d<inf>33</inf>∗) of BT-BNT-xBMT ceramics tend to decrease with increasing BMT concentration.