Temperature-dependent Measurements Research Articles

Electronic properties of polyaniline–graphene nanocomposites synthesized via solution mixing method

A key advantage of combining the exceptional properties of graphene with conducting polymers, lies in their remarkable property tunability through filler additions into polymer matrices, with synthesis routes playing a crucial role in shaping their characteristics. In this work, we examine the electronic properties of polyaniline and graphene nanocomposites synthesized via a simple solution mixing method, which offers advantages such as ease of use and efficiency. Increasing graphene content enhances nanocomposite conductivity, and a percolation effect is observed. The percolation threshold is high and is consistent with a strong role played by voids in the structure. Temperature-dependent conductivity measurements highlight three distinct conduction regimes: insulating, critical, and metallic. These findings underscore the significant influence of synthesis method and structural disorder on shaping electronic properties, paving the way for engineering multifunctional nanocomposites with exceptional versatility and performance.

Enantiomorphic single component conducting nickel(II) and platinum(II) bis(diethyl-dddt) crystalline complexes.

Monoanionic and neutral nickel(II) and platinum(II) bis(dithiolene) complexes based on the 5,6-diethyl-5,6-dihydro-1,4-dithiin-2,3-dithiolate (de-dddt) chiral ligand have been prepared in racemic and enantiopure forms. Neutral closed-shell species have been generated from monoanionic precursors upon electrocrystallization. The racemic anionic (TBA)[Ni(S,S-de-dddt)(R,R-de-dddt)] complex crystallized in the centrosymmetric space group P21/c, while the neutral complexes crystallized in the enantiomorphic tetragonal space group P41212 or P43212. Very subtle conformational differences concerning the orientation of the ethyl substituents are observed between the racemic and the enantiopure compounds, thus impacting the intermolecular interactions at the nanoscale level. Indeed, in the former, the ethyl substituents are all-axial in both independent complexes, while in the latter, one of the independent complexes shows a mixed (eq, eq, ax, ax) conformation and the other independent complex of the asymmetric unit shows the all-axial conformation. Such a tenuous difference at the molecular/nanoscale level strongly impacts the conductivity of the materials. Temperature dependent high pressure single crystal conductivity measurements show activated conductivity for all the materials, with room temperature conductivity values of up to 1.3 × 10-3 S cm-1 for [Ni(S,S-de-dddt)2] at 12.3 GPa and 3.0 × 10-4 S cm-1 for [Pt(R,R-de-dddt)2] at 12.9 GPa. Nevertheless, the racemic compounds are more conductive, i.e. 3.8 × 10-2 S cm-1 for [Ni(rac-de-dddt)2] at 10.0 GPa and 1.5 × 10-3 S cm-1 for [Pt(rac-de-dddt)2] at 10.5 GPa, in agreement with the shorter and more numerous S⋯S intermolecular contacts observed in the crystal structures of the racemic complexes. Moreover, a detailed analysis of DFT calculations suggests that smaller band gaps and higher conductivities should occur for the racemic solids and for the Pt versus Ni complexes.

Eu3+- activated Sr2GdF7 colloid and nano-powder for horticulture LED applications

A series of multifunctional Sr2Gd1-xEuxF7 (x = 0, 0.05, 0.10, 0.40, 0.60. 0.80, and 1.00) phosphors in stable colloidal form and as nanopowders have been prepared using a hydrothermal method. Powder X-ray diffraction analysis confirmed that the materials crystallize in a cubic crystal structure. Transmission electron microscopy shows quasi-spherical nanoparticles with an average particle size of ∼24 nm. Photoluminescence measurements show highly efficient red emission in both colloids and nanopowders, with intensity continually increasing up to 80 mol% of Eu3+ content without concentration quenching. The most prominent emission peaks are around 600 nm (orange/red) and 700 nm (deep red), with the latter more pronounced. Quantum efficiency follows a similar trend, and reaches 60 % for the sample with 80 mol% of Eu3+ content. In addition, similar asymmetry ratio values and CIE coordinates show that there is not a big change in the local symmetry around Eu3+ ions or emission color across the series. This confirms that Eu3+ resides in the same crystalline environment in samples. The observed 5D0-level lifetimes gradually decrease from 12.0 ms to 6.9 ms as the Eu3+ concentration increases. Judd-Ofelt parameters show slight variation with Eu3+ concentration with Ω4 always larger than Ω2. The temperature-dependent steady-state and time-resolved photoluminescence measurements demonstrate high stability of nanopowders’ emission up to 100 °C. The combination of temperature stability and high efficiency of emission, as well as the untypical dominant deep-red emission at 700 nm labels these nanoparticles as potential nanophosphors for various applications.

Possible Superconductivity Transition in Nitrogen-Doped Lutetium Hydride Observed at Megabar Pressure.

The pursuit of room-temperature superconductivity at an accessible synthetic pressure has been a long-held dream for both theoretical and experimental physicists. Recently, a controversial report by Dasenbrock-Gammon et al. claims that the nitrogen-doped lutetium trihydride exhibits room-temperature superconductivity at near-ambient pressure. However, many researchers have failed to independently reproduce these results, which has sparked intense skepticism on this report. In this work, a LuH2±xNy sample is fabricated using high-pressure and high-temperature methods. The composition and structural characterization are the same as the aforementioned near-ambient superconductor. In situ X-ray diffraction investigations indicate that a high-pressure phase transition toward Fm m-LuH3±xNy occurred in the sample at 59GPa. The temperature-dependent resistance measurements reveal that two possible superconductivity transition are observed at 95GPa, with Tc1 ≈6.5 K for high-Tc phase and Tc2 ≈2.1 K for low-Tc phase, arising from the disparate phases in the sample. Resistivity measurements in the Fm m-LuH3±xNy phase under varying magnetic fields exhibited characteristics consistent with superconductivity, with an upper critical field μ0Hc2(0) of 3.3 T measured at 163GPa. This work is expected to shed some light on the controversy surrounding superconductivity in the nitrogen-doped lutetium hydride system.

Correlating Ionic Conductivity to Structure and Dynamics of Li-Ion Battery Electrolyte Systems: Raman Spectroscopy, Dielectric Relaxation Measurements, and Streak Camera Solvation Data Analysis.

A correlation between ionic conductivity and electrolyte solution structure and dynamics was explored by performing electrolyte concentration- and temperature-dependent measurements of conductivity, viscosity, and dielectric relaxation (DR) in solutions of lithium bis(trifluoromethane)sulfonimide (LiTFSI) in triethylene glycol dimethyl ether (also known as triglyme, G3). In addition, an electrolyte concentration-dependent Raman spectroscopic study and ultrafast dynamic fluorescence Stokes shift measurements of solvation of a dissolved solute by employing a streak camera detection technique were carried out. Measured conductivities (σ) and the average DR times (⟨τDR⟩) were found to be partially decoupled from the solution viscosities (η) and obeyed the relation, σ or ⟨τDR⟩-1 ∝(η/T)-p, with p = 0.6-0.75 for σ and p = 0.2-0.45 for ⟨τDR⟩-1. Raman data indicated the formation of ion pairs and ionic aggregates in these solutions, while the measured glass transition temperature increased with LiTFSI concentration. Conductivities (σ) showed a nonlinear concentration dependence but increased linearly with the solution static dielectric constants (εs). The latter may be explained by considering the temperature effects on complex electrolyte species and the subsequent solution dielectric behavior. Interestingly, an inverse power-law dependence of σ on the measured DR or solvation time scales, σ ∝ (τx)-m, with m = 1.2-1.9, was observed. This dependence may be explained by considering that the same environmental friction regulates both the ion diffusion and the medium polarization relaxation. The control of a slow process (ion translation) by relatively faster medium dynamics (dipolar rotation), although quite fascinating for the present system, warrants further experimental scrutiny for other electrolyte systems relevant to battery applications.

Diagnosing the Charge Dynamic Behaviors in Quantum-Dot Light-Emitting Diodes by Temperature-Dependent Measurements.

Distinguishing and understanding the nonradiative recombination of charges are crucial for optimizing quantum-dot light-emitting diodes (QLEDs). Auger recombination (AR), a well-known nonradiative process, is widely recognized to occur in QLEDs. However, it has not yet been directly observed in a real working QLED. Here, the AR effect is verified in the QLED at temperatures of <150 K. At low temperatures, the QLED exhibits a unique S-shaped external quantum efficiency (EQE) evolution as the driving current density increases. Experimental and modeling results indicate that this S-shaped EQE results from the asynchronous changes in the behavior of injection of electrons and holes into the quantum-dot emission layer. At low driving voltages, both electron and hole currents are limited by the Fowler-Nordheim (F-N) tunneling behavior. The relatively low barrier for electrons leads to overwhelming electron injection and seriously imbalanced charges in the quantum dots, triggering the AR process. As the voltage increases, the electron current within the emission layer is no longer governed by F-N tunneling but limited by space charges. Then, charge injection becomes balanced, and the EQE increases. These results offer valuable insights into the charge injection and recombination processes within QLEDs, as well as implications for device design.

On some distinct characteristics of reactive and normal flash sintering: A case study using low-temperature synthesized p-type cuprous delafossite, CuCrO2

We report the rapid synthesis of the high temperature cuprous delafossite (CuCrO2) through a single-step Reactive Flash (RF) method at furnace temperature, Tf=270 ℃ and dc electric field, E≈160 V/cm in ≈ 6.5 min from mixed oxides of Cu and Cr. Besides successful synthesis, we also investigate the larger question of the effect of external dc fields and current on nucleation and growth (N-G) type systems with accompanying compositional changes, typical of chemical reactions. CuCrO2 powders obtained from a hydrothermal route with an abundance of product nuclei were used to investigate the effect on N-G systems with insignificant compositional change (fine-grained/amorphous → coarse-grained). Temperature dependent current measurements towards the end of stage I indicate processes with activation energies of ∼3 eV, suggesting incipient electrochemical and ionic activity. In both scenarios (nucleation, growth, and chemical reactions), the influence of the E-field (Stage I) is far surpassed by the electric current (Stage III) yielding almost single-phase microstructures and p-type conductivity with [h] ≈1014/cm3. Subtle distinctions are identified in the flash characteristics using descriptors including widths of diffraction peaks and average voltage fluctuations.

Effect of 5 MeV proton irradiation on electrical and trap characteristics of β-Ga2O3 power diode

In this study, impact of 5 MeV proton irradiation with radiation fluence of 1013 cm−2 on β-Ga2O3 power diode is investigated by a β-Ga2O3 Schottky barrier diode (SBD). Via temperature-dependent measurements, carrier removal rate RC is determined to be 7.26 × 102 cm−1 at 300 K. Meanwhile, the threshold voltage (Von) and ideality factor (n) almost remain stable after proton irradiation. A close-to-unity n was observed for a wide temperature range indicating near-ideal Schottky characteristics. Dynamic degradation was observed at 300K, but was greatly suppressed at a low temperature of 100K. Meanwhile, two more bulk traps are discovered in proton irradiated β-Ga2O3 SBD by deep-level transient spectroscopy (DLTS). The larger corrected trap concentration (NTa) in proton irradiated β-Ga2O3 SBD was regarded as the reason behind slightly worsened dynamic on-resistance instability at 300 K. Furthermore, lower low frequency noise is revealed for proton irradiated device at room temperature and cryogenic temperature. The study demonstrates the competitive irradiation hardness of β-Ga2O3 power diodes and paves a solid path for the deployment of β-Ga2O3 in space.

Europium spin dilution in the ferromagnetic solid solution Eu4–x Ca x PdMg

Abstract The intermetallic compounds Eu4PdMg and Ca4PdMg form a complete solid solution Eu4–x Ca x PdMg. Further phase analytical studies showed that Eu4PdMg does not allow substitution with strontium. The polycrystalline Eu4–x Ca x PdMg samples were characterized by powder X-ray diffraction. The structure of Eu2.233(6)Ca1.767PdMg was refined from single crystal X-ray diffractometer data: Gd4RhIn type, F 4 ‾ 3m, a = 1,475.42(10) pm, wR2 = 0.0476, 674 F 2 values, 23 variables. Temperature dependent magnetic susceptibility measurements show a drastic decrease of the Curie temperature with increasing calcium substitution. 151Eu Mössbauer spectra of Eu4PdMg and Eu2Ca2PdMg confirm the divalent ground state of europium.

PTHF/LATP Composite Polymer Electrolyte for Solid State Batteries.

The novel crosslinked composite polymer electrolyte (CPE) was developed and investigated using polytetrahydrofuran (PTHF) and polyethyleneglycol diacrylate (PEGDA), incorporating lithium aluminum titanium phosphate (LATP) particles and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt. Composite polymer electrolytes (CPEs) for solid-state lithium-ion batteries (LIBs) were synthesized by harnessing the synergistic effects of PTHF crosslinking and the addition of LATP ceramics, while systematically varying the film composition and LATP content. CPEs containing 15 wt% LATP (PPL15) demonstrated improved mechanical strength and electrochemical stability, achieving a high conductivity of 1.16 × 10-5 S·cm-1 at 80 °C, outperforming conventional PEO-based polymer electrolytes. The CPE system effectively addresses safety concerns and mitigates the rapid degradation typically associated with polyether electrolytes. The incorporation of PEGDA not only enhances mechanical stability but also facilitates lithium salt dissociation and ion transport, leading to a uniform microstructure free from agglomerated particles. The temperature-dependent ionic conductivity measurements indicated optimal performance at lower LATP concentrations, highlighting the impact of ceramic particle agglomeration onion transport pathways. These findings contribute to advancing solid-state battery systems toward practical application.

Increased Formation of Trions and Charged Biexcitons by Above-Gap Excitation in Single-layer WSe2.

Two-dimensional semiconductors exhibit pronounced many-body effects and intense optical responses due to strong Coulombic interactions. Consequently, subtle differences in photoexcitation conditions can strongly influence how the material dissipates energy during thermalization. Here, using multiple excitation spectroscopies, we show that a distinct thermalization pathway emerges at elevated excitation energies, enhancing the formation of trions and charged biexcitons in single-layer WSe2 by up to 2× and 5× , respectively. Power- and temperature-dependent measurements lend insights into the origin of the enhancement. These observations underscore the complexity of excited state relaxation in monolayer semiconductors, provide insights for the continued development of carrier thermalization models, and highlight the potential to precisely control excitonic yields and probe nonequilibrium dynamics in 2D semiconductors.

Colossal Strain Tuning of Ferroelectric Transitions in KNbO3 Thin Films.

Strong coupling between polarization (P) and strain (ɛ) in ferroelectric complex oxides offers unique opportunities to dramatically tune their properties. Here colossal strain tuning of ferroelectricity in epitaxial KNbO3 thin films grown by sub-oxide molecular beam epitaxy is demonstrated. While bulk KNbO3 exhibits three ferroelectric transitions and a Curie temperature (Tc) of ≈676K, phase-field modeling predicts that a biaxial strain of as little as -0.6% pushes its Tc >975K, its decomposition temperature in air, and for -1.4% strain, to Tc >1325K, its melting point. Furthermore, a strain of -1.5% can stabilize a single phase throughout the entire temperature range of its stability. A combination of temperature-dependent second harmonic generation measurements, synchrotron-based X-ray reciprocal space mapping, ferroelectric measurements, and transmission electron microscopy reveal a single tetragonal phase from 10 K to 975K, an enhancement of ≈46% in the tetragonal phase remanent polarization (Pr),and a ≈200% enhancementin its optical second harmonic generation coefficients over bulk values. These properties in a lead-free system, but with properties comparable or superior to lead-based systems, make it an attractive candidate for applications ranging from high-temperature ferroelectric memory to cryogenic temperature quantum computing.

Vanadate Inclusion Leading to Red-Ox-Rich Zircon PrCrO4: Synthesis, Magnetic, and Catalytic Properties.

Rare-earth-based ternary compounds with the formula REBO4 (B = V, Cr, P, As) exhibit rich structural chemistry and associated technologically significant properties. Among the rare-earth chromates, realizing PrCrO4 in a single polymorphic modification has been challenging. Herein, we report the successful stabilization of the zircon polymorph of PrCrO4 by introducing 10 mol % of VO43- instead of CrO43- following a solution combustion method. Compositions with progressively higher amounts of vanadate have been synthesized and characterized extensively. XPS analysis of 10 and 50 mol % VO43- substituted PrCrO4 samples ascertained the existence of Pr3+/4+, Cr4+,5+, and V5+ in them, making it a red-ox-rich system. The tetragonal symmetry of PrCr0.50V0.50O4 was confirmed from the HRTEM images and SAED patterns. FTIR and Raman spectral analyses indicated distorted tetrahedral (Cr/VO4) units with a local site symmetry below D2d. Both d-d and f-f transitions of Cr4+ and Pr3+, respectively, were observed in the absorption spectra. Field and temperature-dependent magnetic measurements of PrCr0.50V0.50O4 confirmed its predominant paramagnetic behavior. The samples possessed porous morphology with a reasonable surface area. PrCr1-xVxO4 (x = 0.00-0.50) samples catalyzed the oxidation of phenol. This study demonstrated B-site tuning in ABO4 systems to select a desired polymorph preferentially.

Peierls Distortion Induced Giant Linear Dichroism, Second-Harmonic Generation, and In-Plane Ferroelectricity in NbOBr2.

The Peierls distortion plays an essential role in governing the in-plane ferroelectricity and nonlinear optical characteristics of anisotropic niobium oxide dihalides, such as NbOCl2 and NbOI2. Despite its significance, experimental investigation into the structural, optical, and ferroelectric properties of NbOBr2 has been lacking. Here, the successful fabrication of centimeter-sized, high-quality NbOBr2 single crystals, enabling direct observation of Peierls distortion using aberration-corrected scanning transmission electron microscopy, is reported. Notably, the magnitude of Peierls distortion in NbOBr2 falls between that observed in NbOCl2 and NbOI2. Furthermore, the existence of giant linear dichroism absorption and second-harmonic generation (SHG) phenomena associated with Peierls distortion is confirmed. Exfoliated NbOBr2 flakes exhibit single-domain ferroelectricity, with the polarization switchable by an electric field. Temperature-dependent SHG measurements reveal a Curie temperature of ≈502K for ferroelectric NbOBr2. This work demonstrates that NbOBr2 holds promise for polarized nonlinear optical devices, as well as for nonvolatile information processing and storage devices.

Enhancement of superconducting properties of grown FeTe0.65Se0.35 single crystals through air annealing

Abstract This work investigates the annealing effects on the superconducting properties of FeTe0.65Se0.35 single crystals. We examine the impact of varying annealing times on the magnetotransport, magnetic, and vortex pinning properties of the single crystals. The structural analysis shows the single crystalline growth of crystals along the c-axis. X-ray photoelectron spectroscopy results confirm the presence of iron oxides in the annealed samples. Temperature-dependent resistivity and magnetization measurements confirm the superconductivity in the as-grown and annealed samples. However, the as-grown sample shows a broad superconducting transition and low superconducting volume fraction, but after annealing, significant improvement in both is observed. Moreover, the self-field critical current density at 2 K is enhanced by a factor of ~4.5 for the optimally annealed sample compared to the as-grown sample. Experimental observations have been analyzed with the theoretical models to understand the effects of annealing on the vortex pinning mechanisms. Further, the specific heat study confirms the bulk superconductivity in the annealed sample compared to the as-grown single crystal. Overall, our study indicates that the superconducting properties vary with the annealing time, and the best results are obtained at an optimum annealing time.

Uncovering upconversion photoluminescence in layered PbI2 above room temperature.

As a van der Waals (vdW) layered semiconductor material, lead iodide (PbI2) possessing a direct bandgap with strong photoluminescence emission in visible range has gained wide attention in applications of photonic and optoelectronic devices. Here, upconversion photoluminescence (UPL) in exfoliated PbI2 flakes is demonstrated at room temperature and elevated temperatures. The linear power dependence of UPL emission with 532nm excitation suggests the one-photon involved multiphonon-assisted UPL emission process, which is revealed by the temperature-dependent UPL emission measurement. Meanwhile, the nonlinear power dependence of UPL emission with 561nm excitation indicates the transition of UPL emission mechanism from linear to nonlinear regime, and the temperature-dependent UPL emission study further shows that the upconversion is contributed by both the multiphonon-assisted UPL process and the two-photon absorption induced PL process. This study will provide an insight to the understanding of photon upconversion in vdW layered semiconductors and advancing applications in temperature-controlled photon upconversion, tunable photonics, photodetection and imaging.

Top-down approach for the preparation of Au/ZnO nanostructures by glancing-angle ion irradiation: Morphological, structural and optical studies

We report the 100 keV glancing-angle Xe+ ions irradiation based top down approach for the preparation of ZnO and Au/ZnO hybrid nanostructures and its morphological, structural and optical properties. FESEM micrographs reveal Xe+ ion irradiation favours the nucleation and formation of highly aligned, dense nanostrips like structures. Crystalline structure of ZnO, Xe+ ions irradiated ZnO and Au/ZnO hybrid nanostructures were analysed by grazing incident X-ray diffraction and Raman scattering measurements. The elemental compositions and thickness of the grown nanostructures were estimated using Rutherford backscattering spectrometry analysis. The influence of Xe+ ion irradiation on the photoluminescence (PL) behaviour of ZnO and Au/ZnO hybrid nanostructures were studied in detail using temperature dependent PL measurements in the range of 80–298 K. Strong PL emission associated with free excitons (FX) and its longitudinal optical phonon replicas observed in ion irradiated Au/ZnO hybrid nanostructures clearly reveal the strong coupling of the localized surface plasmons in the Au nanoparticles to the FX in ZnO. Our experimental results reveal ion beam irradiation is one of the effective approaches to tailor the optical properties of ZnO and Au/ZnO hybrid nanostructures.

Detection of antiferromagnetic order in a RuO2/Pt bilayer by spin Hall magnetoresistance

Altermagnets have spin-split band structures that correspond to the rotational symmetry of the two sublattices in real space. Theoretically, their unique band structures are expected to exhibit intriguing transport phenomena, depending on their magnetic structures. Anomalous Hall effect (AHE) measurement is a method by which to electrically detect magnetic structure and has been reported for typical altermagnets, such as RuO2 and MnTe. However, AHE measurements are limited to specific cases. Thus, it is important to apply other methods by which to determine functionality based on magnetic structure. In this study, we report the spin Hall magnetoresistance (SMR) in a RuO2 (1 nm)/Pt (10 nm) system. A negative SMR signal is clearly observed, indicating the spin-flop antiferromagnetic structure of RuO2. Interestingly, a negative SMR was observed, even at 1 T, which is much smaller than the estimated spin-flop field reported in a previous study. This reflects the thinner film of RuO2 in our study, suggesting that thickness control is effective in adjusting the magnetic anisotropy of RuO2. In addition, the temperature-dependent SMR measurement revealed the Néel temperature of 1 nm thick RuO2 to be 70 ± 9 K. Our results show that SMR measurement can serve as an efficient tool to explore the magnetic features in an altermagnet.

Dynamics of Photoinduced Charge Carriers in Metal-Halide Perovskites.

The measurement and description of the charge-carrier lifetime (τc) is crucial for the wide-ranging applications of lead-halide perovskites. We present time-resolved microwave-detected photoconductivity decay (TRMCD) measurements and a detailed analysis of the possible recombination mechanisms including trap-assisted, radiative, and Auger recombination. We prove that performing injection-dependent measurement is crucial in identifying the recombination mechanism. We present temperature and injection level dependent measurements in CsPbBr3, which is the most common inorganic lead-halide perovskite. In this material, we observe the dominance of charge-carrier trapping, which results in ultra-long charge-carrier lifetimes. Although charge trapping can limit the effectiveness of materials in photovoltaic applications, it also offers significant advantages for various alternative uses, including delayed and persistent photodetection, charge-trap memory, afterglow light-emitting diodes, quantum information storage, and photocatalytic activity.

High temperature thermoelectric properties of BaxSr2−xFeCoO6 double perovskites

Abstract In this study, environmentally benign BaxSr2-xFeCoO6 (BSFC) double perovskites are synthesized via solid-state reaction route for high-temperature thermoelectric applications. The crystal structure and morphology of the ceramic samples are analyzed using XRD and SEM, respectively. Rietveld refinement of XRD data confirms a cubic structure with Pm3̅m space-group. High-temperature thermoelectric measurements exhibits that substituting Ba for Sr in Sr2FeCoO6 increases the Seebeck coefficient (S) but at the expense of the electrical conductivity (σ). The highest Seebeck coefficient of 117 μV/K has been observed in Ba0.5Sr1.5FeCoO6 at 910 K. Temperature-dependent electrical conductivity measurements indicates a semiconductor-to-metal like transition in all samples, with BSFC (x = 0.1) achieving the highest conductivity of 4 × 104 S m−1 at ∼623 K. The thermoelectric power factor has been enhanced by over 50% with Ba substitution in Sr2FeCoO6. Electron transport in these double perovskites is found to follow the small polaron hopping conduction mechanism.