Dielectric relaxation of KH₂PO₄ above room temperature

Abstract

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 − .

Dielectric relaxation of CsHSeO4 above room temperature

“…They argue that regular NH 4 + ions do not have a permanent strong dipole moment, but distortion can induce a dipole and thus, this relaxation can correspond to a reorientation or local jump. Our research team [16][17][18][19] observed that the dielectric response of MH 2 PO 4 (M = K + , NH 4 + ) and L 2 SO 4 (L = K + , Cs + ), reveals a dielectric relaxation at low frequency, for example for K 2 SO 4 around 1.4 × 10 4 Hz at 403 K, which shifts to higher frequencies (~10 6 Hz) as the temperature increases. We have suggested that this dielectric relaxation could be due to the proton jump and phosphate or sulphate reorientation that causes distortion and changes the local lattice polarizability inducing dipoles like H 2 PO 4 − in MH 2 PO 4 (M = K + , NH 4 + ) and like LSO 4 − in L 2 SO 4 (L = K + , Cs + , respectively).…”

Impedance study near the ferroelastic transition in TlH2PO4

“…[2][3][4][5][6][7][8][9] The room temperature phase ͑phase II͒ is known to be paraelectric and ferroelastic while the low-temperature phase ͑phase III͒ is believed to be antiferroelectric. [14][15][16][17] The disorder of the oxygen and hydrogen atoms reflects thermal vibrations and reorientation of the H 2 PO 4 groups. TDP has a monoclinic crystal structure in phases II to III, and an orthorhombic structure in phase I.…”

Dielectric relaxation in Li 2 SO 4 in the intermedia‐temperature regime

“…They argue that regular 4 NH + ions do not have a permanent strong dipole moment, but distortion can induce a dipole and thus, this relaxation can correspond to a reorientation or local jump. Furthermore, our research team [10][11][12] 4 . If the complex permittivity representation of measured dielectric data is used a relaxation is detected as a step in the real part and a peak in the imaginary part of the permittivity.…”