Fundamental Behaviors, and Contributions of Hopping and Tunneling Mechanisms to the Transport Characteristics of the La_0.5Ca_0.5MnO₃ Phase Separated Perovskite

Abstract

A ceramic method was employed to produce a polycrystalline manganite with the nominal composition La0.5Ca0.5MnO3. The single crystallographic phase of La0.5Ca0.5MnO3, with an orthorhombic structure, was confirmed using an X-ray diffraction study. As a phase separation concept, magnetic investigations demonstrate the presence of both charge order-antiferromagnetic (CO-AFM) and ferromagnetic (FM) domains. In the CO-AFM phase, substantial augmentations in magnetization were observed, which were explained by orderly delocalization. Impedance spectroscopy investigation reveals a variety of electrical transport mechanisms at the grains and the grain boundary regions. The direct current conductivity investigation validates the semiconductor behavior of La0.5Ca0.5MnO3. At low temperatures, the transport properties were explained using the Mott-VRH conduction process. For θD/4 ≤ T ≤ θD/2, the electrical conductivity was attributed to the contribution of the Shklovskii–Efros-VRH mechanism. The Shimakawa model was proposed to examine the presence of Coulomb interactions. For T > θD/2, the electrical conductivity was explained using the polaronic hopping process. The electrical conductivity spectra were analyzed using Bruce and Jonscher’s laws. At high frequencies, the electrical response of La0.5Ca0.5MnO3 was explained using the superlinear power law. The contributions of correlated barrier hopping, overlapping large polaron tunneling, and quantum mechanical tunneling conduction processes were predicted via the temperature-dependent frequency exponents. Furthermore, the contribution of polaronic and charge carriers governed the electrical transport phenomenon.

Electrical Conduction Mechanisms in Gd-Substituted WO3 Ceramics: Experimental and Theoretical Approaches

“…In Figure a, fitting of conductivity spectra in the intermediate frequency range (100 kHz–1 MHz) using a modified JPL model yields a frequency exponent of ∼1, indicating nearly constant loss (NCL) behavior. This observation is consistent with the nearly constant value of dielectric loss in this frequency range, supported by the zero slope in the linear fit . Whereas in Figure b, the fitting of conductivity spectra in the intermediate frequency range (500 kHz–2 MHz) using a modified JPL model yields a frequency exponent >1, indicating a superlinear power law (SPL) behavior, which was further validated with the obtained positive slope beyond the minima by the linearly fitted dielectric loss data .…”

“…This observation is consistent with the nearly constant value of dielectric loss in this frequency range, supported by the zero slope in the linear fit. 42 Whereas in Figure 7b, the fitting of conductivity spectra in the intermediate frequency range (500 kHz−2 MHz) using a modified JPL model yields a frequency exponent >1, indicating a superlinear power law (SPL) behavior, which was further validated with the obtained positive slope beyond the minima by the linearly fitted dielectric loss data. 43 Moreover, at high frequencies (>2 MHz), a high frequency plateau (HFP) is observed.…”

Understanding the charge carriers dynamics in the La0.55Ca0.45Mn0.8Nb0.2O3 perovskite: scaling of electrical conductivity spectra

“…In this temperature range, the estimated value of the characteristic temperature coefficient is T 0 = 35 10 5 K. According to previous works, the low-temperature range is characterized by the absence of the Coulomb interactions between the mobile charge carriers. 6,11 The inset of Fig. 4(d) shows the variation of ln(s dc × T 1/2 ) against T −1/2 for the studied ceramic.…”

“…Those materials are used in numerous solid-state devices such as batteries, as they are characterized by the contribution of numerous conduction and polarization processes to transport, relaxation, and dielectric properties. 6 With the development of alternative current conductivity techniques, impedance investigation become a well-conventional description means. Therefore, a variety of theoretical and experimental works is conducted to confirm that the conductivity, for numerous semiconducting compounds, obeys universal laws.…”

“…[7][8][9] Accordingly, it is well-identied that the electrical conductivity of manganites increases rapidly with both frequency and temperature due to the contribution of various hopping and tunneling conduction mechanisms. 6,10,11 Among numerous solid oxides, the manganites-based perovskite family belongs to electronically conducting compounds in which the DC electrical conductivity follows the polaron hopping theory. 12 They are categorized among the materials that reveal scale invariant comportment and offer themselves to simplify and habitually universal description.…”