Maluangnont, Tosapol

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Maluangnont, Tosapol
Alternative Name
Maluangnont, T.
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Email
tosapol.ma@kmitl.ac.th

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    Item type:Publication,
    Interlayer alkali ion governs robustness, reactivity, and dielectric properties of sintered lepidocrocite titanate
    (2022-01-01)
    Maluangnont, Tosapol
    ;
    Pulphol, Phieraya
    ;
    Vittayakorn, Wanwilai
    We investigate the structure across different length scales including the dielectric properties of Cs<inf>0.7</inf>Zn<inf>0.35</inf>Ti<inf>1.65</inf>O<inf>4</inf>, Rb<inf>0.75</inf>Zn<inf>0.375</inf>Ti<inf>1.625</inf>O<inf>4</inf>, and K<inf>0.8</inf>Zn<inf>0.4</inf>Ti<inf>1.6</inf>O<inf>4</inf> sintered at T<inf>S</inf> ​= ​900–1100 ​°C, where the lepidocrocite-type crystal structure is preserved. The increasing interlayer distance in the Rb-/K-analog is explained by the alkali loss which reduces the electrostatic attraction between the sheets and the interlayer ion. Meanwhile, the interlayer contraction in the Cs-analog is rather unusual. The increasing (decreasing) interlayer distances correlate to upshift (downshift) of the Ti-O vibration in the Raman spectra. The three compositions show varied grain orientation depending on the interlayer ion and T<inf>S</inf>. The dielectric permittivity differs by one order of magnitude in the order Cs<inf>0.7</inf>Zn<inf>0.35</inf>Ti<inf>1.65</inf>O<inf>4</inf> « Rb<inf>0.75</inf>Zn<inf>0.375</inf>Ti<inf>1.625</inf>O<inf>4</inf> « K<inf>0.8</inf>Zn<inf>0.4</inf>Ti<inf>1.6</inf>O<inf>4</inf>, suggesting the interlayer ion as the dominating dipole. The influences of T<inf>S</inf>, pellet density (i.e., alkali loss), and grain size/morphology/orientation on the dielectric permittivity are discussed. The understanding of the response to a high temperature treatment would be beneficial not only to specimen fabrications for physical properties measurements, but also to applications where the thermal stability is of concern.
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    Item type:Publication,
    Dielectric Spectroscopy and Electric Modulus Analyses of Ti0.8O2 Nanosheets‒Ag Nanoparticles‒Cellulose Filter Paper Composites
    (2022-01-01)
    Maluangnont, Tosapol
    ;
    Sriphan, Saichon
    ;
    Charoonsuk, Thitirat
    ;
    Vittayakorn, Naratip
    We employ dielectric spectroscopy and the complex electric modulus formalism to characterize electrical properties of the Ti<inf>0.8</inf>O<inf>2</inf> nanosheets‒Ag nanoparticles‒cellulose filter paper composites, intended for use as a triboelectric nanogenerator. The addition of these fillers (5–17 atom% Ti and 1–6 atom% Ag) increases both the dielectric permittivity and AC conductivity while typically keeping the low loss tangent. The observed exponent to the frequency-dependent universal power law indicates the three-dimensional (3D) hopping mechanism in the composited films, contrasting with the 1D- or 2D-conduction in the ceramics. The electrical responses are also distinct from those of sole nanosheets, indicating some filler-matrix interactions. Electric modulus analyses indicate that the Ti<inf>0.8</inf>O<inf>2</inf> nanosheets act as a charge generation/reservoir, while the Ag nanoparticles generate long-range conduction paths. The relaxation time increases with the dielectric nanosheets content but decreases with metallic nanoparticle content. In addition, these co-fillers decrease the dielectric heating but increases the refractive index of the films. The simple analyses reported herein could be applied to other composites, providing a better understanding on the role of diverse functional co-fillers.