Dielectric relaxation and electrothermal charge carrier transport via correlated barrier hopping in the solid electrolyte TlFeP2O7: Experimental and theoretical modeling
Iheb Garoui, Naoufel Ben Hamadi, Saber Nasri, Abderrazek Oueslati, Ahlem Guesmi, Lotfi Khezami, Houcine Naı̈li
Abstract
The interaction between electrical and thermal stimuli reveals the intricate charge dynamics and complex dielectric properties of thallium-iron (III) pyrophosphate (TlFeP 2 O 7 ), highlighting its potential for advanced applications in energy storage and electronic technologies. TlFeP 2 O 7 was synthesized through the traditional solid-state reaction approach. Structural analysis confirmed that the compound crystallizes in a monoclinic structure, indexed in the P2 1 /c space group, exhibiting single-phase formation. The sample's average grain size was around 0.9 μm. Dielectric investigations reveal that TlFeP 2 O 7 displays impressive dielectric properties , including a high dielectric constant (ranging from 10 2 to 3 × 10 4 ) and low dielectric losses (generally less than 30). Additionally, the electrical capacitance shows a promising value of 4.5 μF at 673 K, this suggests that the compound shows promise as a viable candidate for low-frequency energy storage applications. The analysis of complex impedance and electric modulus enables the differentiation between grain and grain boundary contributions to the electrical and dielectric characteristics of the material, revealing non-Debye relaxation behavior. Choosing a suitable equivalent circuit model is crucial for accurately determining DC conductivity parameters from impedance measurements . The semiconducting behavior of TlFeP 2 O 7 is attributed to hopping conduction mechanisms, and the conductivity spectra at various temperatures conform to the straightforward Jonscher power law. The variation of the power law exponent with temperature suggests that charge transport is primarily governed by the correlated barrier-hopping (CBH) mechanism across different temperature and frequency ranges. The maximum barrier energy (W M ) is estimated to be 0.817 eV within the 473–593 K range and 0.441 eV between 613 and 673 K. In summary, this study provides significant insights into the dielectric and charge transport mechanisms of TlFeP 2 O 7 , highlighting its potential for high-performance applications with electro-thermal responsiveness.