Investigation of the structural, morphological, electrical and dielectric properties of Li2CaGeO4 compound

• Published in: Ionics Vol. 30; no. 9; pp. 5325 - 5340
• Main Authors: Yahya, Sourour Ben, Barillé, Regis, Louati, Bassem
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01-09-2024; Springer Nature B.V
• Subjects: Calcium compounds; Ceramic powders; Chemical synthesis; Chemistry; Chemistry and Materials Science; Condensed Matter Physics; Crystallites; Dielectric properties; Dipole interactions; Electrochemistry; Energy Storage; Enthalpy; Frequency ranges; Frequency variation; High temperature; Hopping conduction; Lithium; Optical and Electronic Materials; Parameters; Renewable and Green Energy; Rietveld refinement; Modulus and thermodynamic parameters; CBH model; Li; Permittivity; CaGeO
• ISSN: 0947-7047; 1862-0760
• DOI: 10.1007/s11581-024-05670-7

The synthesis of lithium calcium germanate ceramic powders was achieved through a conventional solid-state reaction method at high temperatures. The formation of the compounds was confirmed using X-ray diffraction and energy dispersive X-ray techniques. Using Scherrer’s formula and Williamson and Hall’s (W–H) method, the average size of the crystallite was found to be 55 nm and 85 nm, respectively. Impedance spectra were measured at temperatures ranging from 553 to 673 K, covering a frequency range of 10 Hz to 1 MHz. The AC conductivity displays frequency-dependent behavior following a variation of the universal power law described by this equation:
σ
AC
(ω) = 
σ
DC
 + A
ω
S
. By analyzing the plot of the pre-exponent S versus temperature, it was determined that the conduction mechanism in the system could be explained using the correlated barrier hopping model. Parameters such as hopping distance
R
ω
and localized state density
N
(
E
F
) were calculated. The behavior of permittivity (
ε
′,
ε″
) and the loss coefficient tan
δ
were attributed to Wagner’s Maxwell theory of interfacial polarization. Complex electric modulus studies confirmed that the relaxation process was thermally activated. Thermodynamic parameters, including the enthalpy Δ
H
and the change in entropy Δ
S
, were calculated. The negative value of Δ
S
indicated the presence of dipole–dipole interactions and the alignment of molecules in the activated state.