Effects of MgO on dielectric properties and electrical conductivity of ternary zinc magnesium phosphate glasses

• Published in: Journal of non-crystalline solids Vol. 355; no. 52; pp. 2533 - 2539
• Main Authors: Khor, S.F., Talib, Z.A., Daud, W.M., Sidek, H.A.A., Ng, B.H.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier B.V 15-12-2009; Elsevier
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Conductivity; Conductivity of specific materials; Dielectric loss and relaxation; Dielectric properties of solids and liquids; Dielectric properties, relaxation, electric modulus; Dielectrics, piezoelectrics, and ferroelectrics and their properties; Disordered solids; Electronic transport in condensed matter; Exact sciences and technology; Permittivity (dielectric function); Phosphates; Physics; Short-range order; 77.22.−d; Phosphates; 72.20.−i; Conductivity; Dielectric properties, relaxation, electric modulus; Short-range order; 72.80.Ng; Frequency dependence; Electrical conductivity; Magnesium oxide; Ternary systems; Liquid state quenching; Phosphate glass; Glass formation; Dielectric relaxation; Temperature effects; 72.20.-i; Zinc oxide; 77.22.-d; Chemical composition; Complex permittivity; Permittivity; Activation energy
• ISSN: 0022-3093; 1873-4812
• DOI: 10.1016/j.jnoncrysol.2009.09.010

Glasses with composition
(
ZnO
)
30
(
MgO
)
x
(
P
2
O
5
)
70
-
x
(
x
=
5, 8, 13, 18 and 20
mol%) have been successfully prepared by the melt-quenching technique. The dielectric permittivity (
ε
′
) and loss factor (
ε
″
) were measured in the frequency range of 0.01
Hz to 1
MHz and in the temperature range of 303 to 573
K. From the results, there is evidence of dipolar relaxation occurring between
10
3
–
10
6
Hz
, while at low frequencies, the spectrum is dominated by dc conduction which was manifested by the
1
/
ω
slope of the loss factor plot. The value of the relaxing frequency (
ω
p
) plotted against
1
/
T
shows a single relaxation mechanism with an activation energy of 0.45
eV. The average value of the activation energy for dc conduction was much higher (1.25
eV) suggesting its diffusion movement had encountered more difficult steps than the small displacement changing dipoles. With increasing MgO concentration, the dielectric permittivity (
ε
′
), dc conductivity (
σ
dc
) and dielectric strength (
Δ
ε
) decrease and these were attributed to some of the magnesium ions participated in the glass-forming positions as well as modifiers. At lower temperatures, the complex permittivity plots present a skewed arc with center point lying below the real axis which is a non-Debye characteristic. The empirical data were sufficiently fitted by using the Harviliak–Negami equation. The temperature dependent of the parameter
α
is discussed.