Summerfield scaling model and conduction processes defining the transport properties of silver substituted half doped (La–Ca) MnO3 ceramic

Abstract

Conductivity spectra of La0.5Ca0.3Ag0.2MnO3 (LCAM) oxide have been investigated in the temperature range [80 K–680 K]. The studied system displays a semiconductor behavior over the explored temperature and frequency ranges. From direct current study, the transport of charge carries is assisted via disorder energy below θD/4. For the temperature range [θD/4- θD/2], the transport properties are governed by activation of Mott-variable range hopping (Mott-VRH) process. Beyond θD/2, the conduction phenomena are assisted through the thermally activation of the small polaron hopping (SPH) mechanism. At high frequencies, the conductivity spectra reveal a dispersive region. They are explained by the double Jonscher response. The latter side was characterized by the appearance of the overlapping-large-polaron-tunneling (OLPT), the correlated barrier hopping (CBH) and the non small polaron tunneling (NSPT) conduction processes. It is found that the calculated disorder energy is frequency independent. At elevated frequencies, the hopping energy is predicted to decrease with increasing frequency which can be related to the change in the Polarons radius. In the temperature range [80 K–220 K], the conductivity spectra follow double Jonscher law. Using the scaling model, the spectra merge into a single master curve, which confirmed the validity of the time temperature superposition principle (TTSP). A confident divergence from the Summerfield is noticed at high frequencies. It proves that the charge mobility is temperature dependant. The Summerfield correction scaling is effectuated by introducing a scaling positive parameter (α = 1.2). An excellent coalescence of conductivity spectra is observed.