Complex impedance study of KDP protonic conductivity

Oliveira, A.L. de; Damasceno, O. de O.; Oliveira, Jéssica de; Schouler, E.J.L.

doi:10.1016/0025-5408(86)90174-1

Cited by 10 publications

(3 citation statements)

References 22 publications

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“…Considering the existence of two dispersion mechanisms and the bulk conductance G 1 and the surface conductance G 2 of the material, an equivalent circuit can be proposed, as shown in figure 7 [28,39]. The overall impedance spectra of RbH 2 PO 4 are similar to that reported previously for KH 2 PO 4 [27,28].…”

Section: Impedance Spectroscopysupporting

confidence: 68%

“…Lee claimed that the high-temperature anomaly should be interpreted as an onset of partial polymerization at reaction sites at the surface of solids (see figure 7 in [26]). A similar high-temperature phenomenon has been much studied in KH 2 PO 4 around T p (170-225 • C) [7,14,19,22,27,28,29,30], but recent experimental results verified the evidence of a chemical reaction of the type in (1) at the surface rather than polymorphic structural phase transition [14,28,29,30]. Therefore, referring to the similar natures of the high-temperature phenomena of RbH 2 PO 4 and KH 2 PO 4 , there still remains a question whether the high-temperature anomaly of RbH 2 PO 4 is a structural phase transition or thermal decomposition.…”

Section: Introductionsupporting

confidence: 53%

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Surface instability and possible polymerization in at high temperatures

Park

Lee

Jungnam

1998

J. Phys.: Condens. Matter

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We have investigated in detail the high-temperature phenomena of RbH 2 PO 4 by means of optical microscopy, differential scanning calorimetry (DSC), and impedance spectroscopy. The so-called high-temperature transformation temperature T p is scattered widely over the temperature range of 82-117 • C, depending strongly upon the experimental conditions such as sample quality and experimental probes. It has been observed by thermomicroscopy that, upon heating above 110 • C, the cracks appeared at the surface and the crack pattern grew up with increasing temperature above 110 • C, and on suitable prolonged heat treatment at constant temperature near 110 • C. The activation energy is estimated from DSC, which revealed the wide scatter of T p over the range 82-117 • C. The complex ac impedance spectra near 113 • C were fitted by superposition of two Cole-Cole types of relaxations. The fast component is interpreted as proton migration in the bulk, while the slow component is accounted for as a cluster formation due to breaking and reforming of the hydrogen bond at the surface.Our results show evidence that the high-temperature phenomenon of RbH 2 PO 4 near T p is not a polymorphic structural phase transition of the tetragonal phase to a presumed monoclinic modification, but a slow partial polymerization of RbH 2 PO 4 into Rb n H 2 P n O 3n+1 (probably n = 2) at reaction sites at the surface of crystal. The high-temperature phenomenon is believed to be controlled by the topochemical factors.

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Section: Impedance Spectroscopysupporting

confidence: 68%

Section: Introductionsupporting

confidence: 53%

Surface instability and possible polymerization in at high temperatures

Park

Lee

Jungnam

1998

J. Phys.: Condens. Matter

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“…The single crystal KDP shows a similar behaviour but the conductivity values are somewhat lower. The activation energies obtained in earlier works on KDP polycrystalline by de Oliveira et al [13] and by Baranov et al [14] were 0.99 eV and 0.82 eV, respectively. Recently, J. H. Park [15] has reported activation energies of 0.68 eV for KDP crystals.…”

Section: Methodsmentioning

confidence: 89%

Dielectric relaxation of KH₂PO₄ above room temperature

Diosa¹,

Vargas

Albinsson

et al. 2004

Physica Status Solidi (b)

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The dispersion curves of the dielectric response of KH 2 PO 4 were obtained from 5 Hz to 13 MHz and over the temperature range 120 -206 °C for both single crystal and polycrystalline samples. Both types of samples reveal dielectric relaxation at low frequency, for example around 10 4 Hz at 140 °C, which shifts to higher frequencies (~1 MHz) as the temperature increases. The relaxation frequency was determined from the peak obtained in the imaginary part of the permittivity as well as from the derivative of the real part of the permittivity. The activation energy E a = 0.82 eV, obtained from the relaxation frequency is very close to that derived from the dc conductivity. We suggest that this dielectric relaxation could be due to the proton jump and phosphate reorientation that causes distortion and change the local lattice polarizability inducing dipoles like 2 4 H PO − .

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