Understanding charge transport and dielectric relaxation properties in lead-free Cs2ZrCl6 nanoparticles.

In the exploration of perovskite materials devoid of lead and appropriate for capturing solar energy, a recent finding has surfaced concerning Cs2ZrCl6. This compound has attracted interest as a potential candidate, displaying advantageous optical and electrical features, coupled with remarkable durability under environmental stresses. This research outlines the effective production of non-toxic metal halide nanoparticles of Cs2ZrCl6 using the gradual cooling technique. Thorough examinations have been conducted to explore the structural, optical, and dielectric traits. Over the frequency range of 101-106 Hz, the dielectric constant, loss factor, electric modulus, and electrical conductivity of Cs2ZrCl6 exhibit a strong dependence on temperature. The Nyquist plot confirms the distinct contributions of grains and grain boundaries to the total impedance. In the high-frequency region, the dielectric constant tends to increase with temperature. In accordance with the modified Kohlrausch-Williams-Watts (KWW) equation, an asymmetric nature corresponding to the non-Debye type is observed in the electric modulus spectra at different temperatures. Furthermore, the imaginary part of the electric modulus spectrum shifts from the non-Debye type towards the Debye type with increasing temperature, despite not obtaining an exact Debye response. The frequency-dependent behavior of AC conductivity has been modeled using Joncher's universal law. The conduction mechanism within the Cs2ZrCl6 compound is attributed to the small polaron tunneling model (NSPT). Furthermore, Cs2ZrCl6 has the potential to function as an energy harvesting device due to its elevated dielectric constant combined with minimal dielectric loss.

Structural, morphological, electrical, and dielectric properties of Na2Cu5(Si2O7)2 for ASSIBs.

Solid inorganic electrolyte materials are fundamental components for constructing all-solid-state sodium-ion batteries. These solid electrolytes offer considerable benefits related to safety, electrochemical performance, and mechanical stability in comparison to liquid organic electrolyte systems. This study investigates the sodium ion conduction mechanism and relaxation kinetics in the sorosilicate material Na2Cu5(Si2O7)2, a potential solid electrolyte, using impedance spectroscopy. Analysis of the DC conductivity data demonstrates that sodium ion mobility follows Arrhenius behavior with a thermal activation energy barrier of 1.21 eV. This work highlights the importance of carefully choosing an appropriate equivalent circuit model to extract DC conductivity parameters from impedance data, given the contributions from both grain and grain boundary effects. Analysis of the AC conductivity and dielectric constant as a function of frequency and temperature demonstrates that ionic conduction takes place in this material through a process in which charge carriers overcome correlated energy barriers, known as correlated barrier hopping. The neutron diffraction patterns were analyzed using soft bond valence sum (BVS) techniques to map the possible ionic conduction pathways within the unit cell. Examination of the data points to obstructions in the sodium ion diffusion routes along the a-axis and diagonal of the bc plane within the triclinic unit cell. These bottlenecks likely contribute to the high activation energy and correspondingly low ionic conductivity observed. Analysis of dielectric properties by modulus verified that the ionic conduction relaxation phenomena exhibit thermal activation and a distribution of relaxation times. In summary, this work elucidates the microscopic ionic conduction mechanism in Na2Cu5(Si2O7)2 through extensive analysis encompassing DC/AC conductivity, electric modulus, and dielectric constant measurements. The insights gained into the ionic conduction mechanism will aid in engineering optimized ionic conductor materials for battery technologies.

Morphological, structural, optical and dielectric analysis of Cs2TiBr6 perovskite nanoparticles.

In the pursuit of lead-free perovskite materials suitable for harnessing solar energy, a recent discovery has emerged regarding Cs2TiBr6. This compound has garnered attention as a prospective candidate, exhibiting favorable optical and electrical characteristics alongside exceptional resilience when subjected to environmental strains. This study details the successful synthesis of non-hazardous metal halide nanoparticles of Cs2TiBr6via the slow cooling method. Comprehensive investigations into the structural, optical, and dielectric characteristics have been undertaken. The temperature sensitivity of various electrical properties, including the dielectric constant, loss factor, electric modulus, and AC/DC conductivity, is evident in this perovskite material. This phenomenon is observed across a frequency range of 1 to 107 Hz. Furthermore, examination of the Nyquist plot highlights the distinctive contributions of both grain and grain boundaries to the overall impedance characteristics. In the high-frequency range, it is observed that the dielectric constant exhibits an upward trend as the temperature rises. Examination of the adapted Cole-Cole plot unveils that both space charge and free charge conductivity escalate with increasing temperature, while concurrently, the relaxation time experiences a reduction with the temperature's ascent. We observed an asymmetrical pattern in the electric modulus spectra at varying temperatures using a modified Kohlrausch-Williams-Watts equation. This asymmetry is consistent with the inherent non-Debye nature of perovskite materials. Additionally, as the temperature increases, we note a shift in the imaginary component of the electric modulus spectra, transitioning from a non-Debye character towards a semi-Debye nature, though it does not achieve a strictly Debye-type response. This transformation indicates the semiconducting properties of the material. We elucidate the AC conductivity behavior in Cs2TiBr6 by employing the non-overlapping small-polaron tunneling (NSPT) mechanism as the basis. The activation energy, as determined from both the modulus spectra and DC conductivity, aligns closely, providing robust evidence for the congruence between the relaxation dynamics and the conduction mechanism. In addition to these attributes, Cs2TiBr6 exhibits a substantial dielectric constant coupled with negligible dielectric loss, thus establishing its potential suitability for energy harvesting devices.

Interpretation of dielectric behavior and polaron hopping in lead-free antimony-based double perovskite.

Lately, double perovskite materials have become well-known in the commercialization area owing to their potential use in optoelectronic applications. Here, double perovskite Cs2AgSbCl6 single crystals (SCs) with cubic crystal structure and Fm3̄m space group were successfully synthesized via the slow cooling technique. This paper investigates the dielectric relaxation and charge transfer mechanism within Cs2AgSbCl6 using electrochemical impedance spectroscopy (EIS) in the 273-393 K temperature range under light. The dielectric response in Cs2AgSbCl6 has been explained by the space charge polarization and the ionic motion. The ε'(ω) study at different temperatures shows a remarkable frequency transition at which dε'/dT changes from a positive to a negative coefficient. Based on Stevels approach, the density of traps diminishes with the temperature increase, which improved conduction. However, this approach proves the polaronic conduction in Cs2AgSbCl6. 0.42 and 0.21 eV are the binding (Ep) and polaron hopping (WH) energy values, respectively. Contrary to free-charge carrier motion, polaron hopping was proposed as the principal conduction process since the ambient-temperature thermal energy was lower than Ep. Moreover, the analysis of M''(ω) and -Z''(ω) as a function of temperature shows the thermally-activated relaxation from the non-Debye to Debye type model in Cs2AgSbCl6. This scientific research offers an essential understanding of the dielectric relaxation behavior, which is required for improving dielectric switches. Also, this paper provides a deep insight into the conduction mechanism within double perovskite materials.

Lead-free double perovskite Cs2MBiCl6 (M = Ag, Cu): insights into the optical, dielectric, and charge transfer properties.

Recently, double perovskites have shown excellent potential considering the instability and toxicity problems of lead halide perovskites in optoelectronic devices. Here, the double perovskites Cs2MBiCl6 (M = Ag, Cu) were successfully synthesized via the slow evaporation solution growth technique. The cubic phase of these double perovskite materials was verified through the X-ray diffraction pattern. The investigation of Cs2CuBiCl6 and Cs2AgBiCl6 utilizing optical analysis showed that their respective indirect band-gap values were 1.31 and 2.92 eV, respectively. These materials, which are double perovskites, were examined using the impedance spectroscopy technique within the 10-1 to 106 Hz frequency and 300-400 K temperature ranges. Jonncher's power law was utilized to describe AC conductivity. The outcomes of the study on charge transportation in Cs2MBiCl6 (where M = Ag, Cu) suggest that the non-overlapping small polaron tunneling mechanism was present in Cs2CuBiCl6, whereas the overlapping large polaron tunneling mechanism was present in Cs2AgBiCl6.

Study of charge transfer mechanism and dielectric relaxation of all-inorganic perovskite CsSnCl3.

In the field of commercialization, lead-free metal halide perovskite materials are becoming more popular these days because of their prospective use in solar cells and also in other optoelectronic applications. In this paper, a non-toxic CsSnCl3 metal halide is successfully synthesized via the slow evaporation solution growth technique. Such systematic characterizations as differential scanning calorimetry (DSC) measurements, dielectric measurements, and variable-temperature structural analyses indicate that CsSnCl3 goes through a reversible phase transformation at T = 391/393 K from the monoclinic to the cubic system. Optical measurements of CsSnCl3 reveal a direct band-gap value of about 3.04 eV. The study of the charge transfer mechanism of CsSnCl3 is carried out based on Elliott's theory. The conduction mechanism in CsSnCl3 is interpreted through the following two approaches: the non-overlapping small polaron tunneling (NSPT) model (monoclinic phase) and the overlapping large polaron tunneling (OLPT) model (cubic phase). Moreover, the high dielectric constant of CsSnCl3 which is associated with a low dielectric loss makes it a possible candidate for energy harvesting devices.