Effect of ethylene carbonate plasticizer on agar-agar: NH<Subscript>4</Subscript>Br-based solid polymer electrolytes

Proton-conducting polymer electrolytes based on biopolymer, agar-agar as the polymer host, ammonium bromide (NH₄Br) as the salt and ethylene carbonate (EC) as the plasticizer have been prepared by solution casting technique with dimethylformamide as solvent. Addition of NH₄Br and EC with the biopolymer resulted in an increase in the ionic conductivity of polymer electrolyte. EC was added to increase the degree of salt dissociation and also ionic mobility. The highest ionic conductivity achieved at room temperature was for 50 wt% agar/50 wt% NH₄Br/0.3% EC with the conductivity 3.73?×?10^?4 S cm^?1. The conductivity of the polymer electrolyte increases with the increase in amount of plasticizer. The frequency-dependent conductivity, dielectric permittivity (ε′) and modulus (M′) studies were carried out.     

The role of zirconium oxide as nano-filler on the conductivity,morphology, and thermal stability of poly(methyl methacrylate)–poly(styrene-co-acrylonitrile)-based plasticized composite solid polymer electrolytes

The plasticized composite solid polymer electrolytes (CSPE) involving polymer blends poly(methyl methacrylate)-poly(styrene-co-acrylonitrile) (PMMA-SAN), plasticizers ethylene carbonate (EC), and propylene carbonate (PC) with lithium triflate (LiCF₃SO₃) as salt and varying concentration of composite nano-filler zirconium oxide (ZrO₂) is prepared by solution casting technique using THF as solvent. The powder X-ray diffraction (XRD) studies reveal amorphous nature of the CSPE samples. Fourier transform infrared (FT-IR) spectroscopy studies reveal interaction of Li⁺ ion with plasticizers, both C=O and OCH₃ group of the PMMA, while nitrile group of SAN is inert. AC impedance and dielectric studies reveal that the ionic conductivity (σ), dielectric constant (ε’), and dielectric loss (ε”) of the prepared CSPE samples increase with increasing content of ZrO₂ nano-filler up to 6 wt% and decrease with further additions. The temperature dependence of ionic conductivity follows Arrhenius relation and indicates ion-hopping mechanism. The sample Z2 (6 wt% ZrO₂) with relaxation time τ of 8.13?×?10^–7 s possess lowest activation energy (E_a?=?0.23 eV) and highest conductivity (2.32?×?10^–4 S cm^?1) at room temperature. Thermogravimetric analysis (TGA) reveals thermal stability of highest conducting sample Z2 up to 321 °C after complete removal of residual solvent, moisture, and its impurities. Differential scanning calorimetric (DSC) studies reveal absence of glass transition temperature (T_g) corresponding to atactic PMMA for the CSPE Z2, while isotactic PMMA component shows T_g around 70 °C, which is due to increased interaction of filler with PMMA leading to change in its tacticity. Scanning electron microscopy (SEM) analysis reveals blending of PMMA/SAN polymers and lithium triflate salt. The incorporation of nano-filler ZrO₂ leads to change in surface topology of polymer matrix. Rough surface of the CSPE Z2 leads to new pathway for ionic conduction leading to maximum ionic conductivity.     

Study of the anisotropy of the dielectric response of Na<Subscript>1/2</Subscript>Bi<Subscript>1/2</Subscript>TiO<Subscript>3</Subscript> relaxor ferroelectric

The dielectric response, conductivity, and domain structure of (Na_1/2Bi_1/2)TiO₃ single crystals are studied in the temperature range of 290–750 K for the [100], [110], and [111] crystallographic directions. It is shown that the region of optical isotropization is observed in polarized light in the temperature range of 570–620 K. In this case, the birefringence (Δn) decreases and disappears (together with the image of the domain structure) for the [100] directions. The region of optical isotropization in the [111] directions is characterized by the disappearance of the image of the domain structure and by the existence of individual regions with partial quenching. The domain structure in the [110] directions remains distinguished against the background of a significant decrease in Δn in the indicated temperature range. The region of isotropization is also manifested in the temperature dependence of the imaginary part of the dielectric response and is determined by the isotropic character of the conductivity in the range of 570–620 K. The bulk conductivity has a thermally activated character with activation energies E _a = 50?60 meV at T < 500 K and E _a = 700?900 meV for T > 620 K. The low-frequency dispersion of the dielectric response is determined by the Maxwell–Wagner mechanism and is due to an increase in the ionic conductivity at temperatures above 620 K. The anisotropy of the susceptibility holds in the entire studied ranges of frequencies (25 Hz–1 MHz) and temperatures.     

Ion dynamics in methylcellulose–LiBOB solid polymer electrolytes

A polymer electrolyte system comprising methylcellulose (MC) as the host polymer and lithium bis(oxalato) borate (LiBOB) as the lithium ion source has been prepared via the solution cast technique. The electrolyte with the highest conductivity of 2.79 μS cm^?1 has a composition of 75 wt% MC–25 wt% LiBOB. The mobile ion concentration (n) in this sample was estimated to be 5.70?×?10²⁰ cm^?3. A good correlation between ionic conductivity, dielectric constant, and free ion concentration has been observed. The ratio of mobile ion number density (n) at a particular temperature to the concentration n ₀ of free ions at T?=?∞ (n/n ₀) and the power law exponents (s) exhibit opposite trends when varied with salt concentration.     

Polymer electrolytes based on vinyl ethers with various EO chain length and their polymer electrolytes cross-linked by electron beam irradiation

Polymer electrolytes based on vinyl ethers with various ethyleneoxy (EO) chain length (poly-1a (m?=?3), poly-1b (m?=?6), poly-1c (m?=?10), and poly-1d (m?=?23.5)) with lithium bis(trifluoromethanesulfonimide) (LiTFSI) were prepared, and effect of pendant EO chain length in the polymers on electrochemical and thermal properties was investigated. Glass transition temperature (T _g) of all polymer electrolytes increased linearly with an increase in salt concentrations. Ionic conductivities of the polymer electrolytes increased with an increase in the pendant EO chain length of the polymers at the constant [Li]/[O] ratio, but in the polymer electrolyte of the poly-1d (m?=?23.5) with the longest pendant EO chain length, ionic conductivity decreased in the low temperature range of ?20 to 10 °C due to the crystallization of the pendant EO chain. The highest ionic conductivity, 1.23?×?10^?4 S/cm at 30 °C, was obtained in the polymer electrolyte of the poly-1c (m?=?10) with pendant EO chain length of 10 at the [Li]/[O] ratio of 1/20. It was found that the cross-linking of the polymer electrolyte, composed of poly-1c (m?=?10) with LiTFSI at the [Li]/[O] ratio of 1/28, by electron beam (EB) irradiation may improve the mechanical property without affecting ionic conductivity, thermal property, and oxidation stability. Polymer electrolytes based on poly-1a (m?=?3), poly-1b (m?=?6), poly-1c (m?=?10), and poly-1d (m?=?23.5) and cross-linked polymer electrolytes were electrochemically stable until 4 V and thermally stable around 300 °C.     

Effect of the hexagonal warping on the dynamical conductivity of surface states in a topological insulator

We report on the effect of hexagonal warping on the dynamical conductivity of the surface states of a topological insulator in the presence of nonmagnetic impurities. It is found that the photon energy dependent conductivities are determined by a polarization-function-liked term,  Π₂ (q,ω), which contains a velocity term corresponding to the difference of group velocities between the two states due to an electron-impurity scattering. This is different from the conductivity of 2-dimentional electron systems where the conductivity depends on the inverse imaginary part of the dielectric function Im [1/κ(q,ω)]. We present both the real part and imaginary part of the polarization function with different warping strength. It is found that the warping strength can both enhance single particle excitations (SPEs) and suppress the screening effect of electrons. As a result the inverse scattering time is enhanced by up to about two orders of magnitudes. The real part of the longitudinal conductivity of the intra-band process is analog to the case with a conductivity of σ ~ μδ(ω). The broadening of the spectrum in the low energy is not only determined by chemical potential, but also dependent on the warping strength. At higher frequency, the real part of conductivity shows a jump at the threshold photon energy of μ, where the inter-band contribution takes over.     

Enhancement of the electrochemical properties with the effect of alkali metal systems on PEO/PVdF-HFP complex polymer electrolytes

Polymer blend electrolytes based on poly(ethylene oxide) (PEO) and poly(vinylidene fluoride-hexafluoropropylene) (PVdF-HFP) were prepared by using different lithium salts LiX (X = ClO₄, BF₄, CF₃SO₃, and N [CF₃SO₂]₂) using solution casting technique. To confirm the structure and complexation of the electrolyte films, the prepared electrolytes were subjected to X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analysis. Alternating current (AC) impedance analysis was performed for all the electrolyte samples at various temperatures from 303 to 343 K. The result suggests that among the various lithium salts, LiN[CF₃SO₂]₂-based electrolytes exhibited the highest ionic conductivity at 8.20 × 10^?4 S/cm. The linear variation of the ionic conductivity of the polymer electrolytes with increasing temperature suggests the Arrhenius-type thermally activated process. Activation energies were found to decrease when doping with lithium imide salt. The dielectric behavior has been analyzed using dielectric permittivity (ε*), electric modulus (M*), and dissipation factor (tanδ) of the samples. Cyclic voltammetry has been performed for the electrolyte films to study their cyclability and reversibility. Thermogravimetric and differential thermal analysis (TG/DTA) was used to ascertain the thermal stability of the electrolytes, and the porous nature of the electrolytes was identified using scanning electron microscopy via ion hopping conduction. Surface morphology of the sample having maximum conductivity was studied by an atomic force microscope (AFM).     

Effects of ionic liquid on the hydroxylpropylmethyl cellulose (HPMC) solid polymer electrolyte

Biodegradable solid polymer electrolyte (SPE) is prepared by solution-casting technique using low-cost cellulose derivative, hydroxypropylmethyl cellulose (HPMC) as a host polymer. Owing to the hydrophobic nature of this polymer, it is predicted to exhibit low ionic conductivity upon addition of magnesium trifluoromethanesulfonate (MgTf₂) salt. Therefore, ionic liquid (IL), 1-butyl-3-methylimidazolium trifluoromethanesulfonate (BMIMTf), is added in order to enhance its ionic conductivity. Based on the findings, the ionic conductivity at room temperature and the dielectric behaviors of the SPE complex improved upon incorporation of 40 wt.% IL. On top of that, addition of IL reduces the degree of crystallinity and the glass transition temperature (T _g ) of the SPE. The conductivity-temperature plot revealed that the transportation of ions in these films obey Arrhenius theory. The interaction between SPE complex, MgTf₂ salt, and BMIMTf is investigated by means of Fourier transform infrared (FTIR) spectroscopy through the change in peak intensity around 3413, 1570, and 1060 cm^?1, which are responsible for –OH stretching band, C–C and C–N bending modes of cyclic BMIM⁺, and C–O–C stretching band, respectively.     

Characterization of PEO/PVP/GO nanocomposite solid polymer electrolyte membranes: microstructural,thermo-mechanical,and conductivity properties

Poly (ethylene oxide) (PEO)/polyvinylpyrrolidone (PVP) blended nanocomposite polymers, incorporating graphene oxide (GO) nano-sheets and embedded with NaIO₄ salt, were prepared using solution casting technique. The as-prepared nanocomposite electrolyte membranes were characterized by SEM, TEM, XRD, and Raman vibrational spectroscopic techniques to confirm the dispersion of GO nano-sheets and to understand the synergistic properties of GO/polymer interactions as a function of GO nano-sheets concentration. GO fillers incorporated electrolyte membranes demonstrated distinctive surface morphology composed of circular-shaped protuberances of different dimensions. The decrease of Raman intensity ratio (I_D/I_G) and in-plane crystallite size (L_a) values of the nanocomposites suggested the good dispersion and confinement of the GO nano-sheets. The optical properties of blend electrolyte films were studied as a function of GO filler concentration using optical absorption and diffuse reflectance spectra. In reference to PEO/PVP/NaIO₄, the resultant PEO/PVP/NaIO₄/GO (0.4% in weight) electrolyte membrane demonstrated both an increase in tensile strength of ca. 42% and in Young’s modulus of ca. 40%, improvements coupled with a maximum fractured elongation of 3%. Through impedance spectroscopy analysis, the role of the GO nano-sheets onto the room temperature conductivity properties of the prepared electrolyte membranes has been probed.     

Ionic conduction mechanism and relaxation studies of NaNbAlP<Subscript>3</Subscript>O<Subscript>12</Subscript> compound

The Na superionic conductor (NASICON) NaNbAlP₃O₁₂ compound was prepared by the conventional solid-state reaction method. The formation of single-phase material was confirmed by X-ray diffraction studies, and it was found to be a hexagonal phase at room temperature. The electrical conductivity was measured in the frequency range from 200 Hz to 5 MHz and temperatures between 573 and 773 K using impedance spectroscopy technique. The obtained results were analyzed by fitting the experimental data to the equivalent circuit model. The analysis of Nyquist plots has revealed the contribution of three electrically active regions corresponding to the bulk mechanism, distribution of grain boundaries, and electrode processes. Besides, the frequency dependence of the conductivity is interpreted in terms of Jonscher’s law. Temperature dependence of the power law exponent s strongly suggests that the non-overlapping small polaron tunneling (NSPT) model is the dominant transport process. The variation of the imaginary part of the complex modulus as a function of angular frequency at several temperatures shows a double relaxation peak suggesting the presence of grains and grain boundaries in the sample. An analysis of the dielectric constants ε″ and loss tangent tan (δ) with frequency shows a distribution of relaxation times.     

Green electrolytes based on dextran-chitosan blend and the effect of NH<Subscript>4</Subscript>SCN as proton provider on the electrical response studies

Dextran-chitosan blend added with ammonium thiocyanate (NH₄SCN)-based solid polymer electrolytes are prepared by solution cast method. The interaction between the components of the electrolyte is verified by Fourier transform infrared (FTIR) analysis. The blend of 40 wt% dextran-60 wt% chitosan is found to be the most amorphous ratio. The room temperature conductivity of undoped 40 wt% dextran-60 wt% chitosan blend film is identified to be (3.84?±?0.97)?×?10^?10 S cm^?1. The inclusion of 40 wt.% NH₄SCN to the polymer blend has optimized the room temperature conductivity up (1.28?±?0.43)?×?10^?4 S cm^?1. Result from X-ray diffraction (XRD) and differential scanning calorimetry (DSC) analysis shows that the electrolyte with the highest conductivity value has the lowest degree of crystallinity (χ _c) and the glass transition temperature (T _g), respectively. Temperature-dependence of conductivity follows Arrhenius theory. From transport analysis, the conductivity is noticed to be influenced by the mobility (μ) and number density (n) of ions. Conductivity trend is further verified by field emission scanning electron microscopy (FESEM) and dielectric results.     

Effect of doping by boron,carbon, and nitrogen atoms on the magnetic and photocatalytic properties of anatase

The effect of doping of titanium dioxide with the anatase structure by boron, carbon, and nitrogen atoms on the magnetic and optical properties and the electronic spectrum of this compound has been investigated using the ab initio tight-binding linear muffin-tin orbital (TB-LMTO) band-structure method in the local spin density approximation explicitly including Coulomb correlations (LSDA + U) in combination with the semiempirical extended Hückel theory (EHT) method. The LSDA + U calculations of the electronic structure, the imaginary part of the dielectric function, the total magnetic moments, and the magnetic moments at the impurity atoms have been carried out. The diagrams of the molecular orbitals of the clusters Ti₃ X (X = B, C, N) have been calculated and the pseudo-space images of the molecular orbitals of the clusters have been constructed. The effect of doping on the nature and origin of photocatalytic activity in the visible spectral range and the specific features of the generation of ferromagnetic interactions in doped anatase have been discussed based on the analysis of the obtained data. It has been shown that, in the sequence TiO_{2 ? y} N _y → TiO_{2 ? y} C _y → TiO_{2 ? y} B _y (y = 1/16), the photocatalytic activity can increase with the generation of electronic excitations with the participation of impurity bands. The calculated magnetic moments for boron and nitrogen atoms are equal to 1 μ_B, whereas the impurity carbon atoms are nonmagnetic.     

Thermooptical and Dielectric Studies of a Calcium-Induced Ferroelectric Phase in a SrTiO<Subscript>3</Subscript> Incipient Ferroelectric

We have examined temperature changes of the light refraction, birefringence, dielectric permittivity, and dielectric hysteresis loops in Sr_{1 – x}Ca_xTiO₃ single crystals with x = 0.014 (SCT-1.4). The dielectric properties of Sr_{1 – x}Ca_xTiO₃ with x = 0.007 (SCT-0.7) have been studied. We have performed ab initio calculations of equilibrium structures and total energies for three low-temperature phases of SrTiO₃ and CaTiO₃, based on which we have determined an expected symmetry of the ground state of their solid solution and spontaneous polarization directions in a calcium-induced ferroelectric phase in Sr_{1 – x}Ca_xTiO₃. In SCT-1.4, we have separated a spontaneous contribution to the light refraction, which arises due to the spontaneous electrooptical effect caused by the spontaneous polarization and its fluctuations. From the spontaneous contribution to the light refraction, based on a previously developed our phenological approach, we have quantitatively determined for the first time the values and temperature dependences of root-mean-square fluctuations of the order parameter—the polarization P_sh = 〈P _fl ² 〉^1/2(short-range, local polar order) in the ferroelectric phase. From optical and dielectric measurements in SCT-1.4, the average value of spontaneous polarization P_s (the contribution from the long-range order) has been determined. We have estimated the values of P_sh and P_s, which characterize the short- and long-range orders in the ferroelectric phase of SCT-0.7. Separate determination of the values and temperature dependences of P_s and P_sh (which considerably exceeds the value of P_s in the ordered phase) has allowed us to reveal on a quantitative level new particular features of the formation of the induced polar phase in Sr_{1 – x}Ca_xTiO₃.     

Biodegradable poly <Emphasis>(</Emphasis>ε<Emphasis>-</Emphasis>caprolactone<Emphasis>)/</Emphasis>lithium bis<Emphasis>(</Emphasis>trifluoromethanesulfonyl<Emphasis>)</Emphasis> imide as gel polymer electrolyte

Poor conductivity and toxic technological garbage of polymer electrolyte has delayed energy storage application in electric vehicles. Biodegradable gel polymer electrolytes (GPEs) based on poly (ε-caprolactone) (PCL) are prepared. PCL is used to immobilize liquid electrolyte containing lithium bis(trifluoromethanesulfonyl) imide, ethylene carbonate, and propylene carbonate. Impedance spectroscopy, X-ray diffraction, and differential scanning calorimetry are used to characterize the ionic conductivity and structural and thermal properties of GPEs, respectively. For jelly-like GPEs, it exhibits liquid-like ionic conductivity of 1.69 × 10^?3 S cm^?1 at room temperature with a composition ratio (PCL:LiTFSI:EC:PC) of (22.5:7.5:35:35) (w/w). Results show that the polymer matrix forms cross-linked network within the liquid electrolyte, acting like an adhesive to hold the high fluidity liquid molecules. In temperature dependence studies, the GPEs are observed to obey Arrhenius equation indicating that ion transport occurs via hopping mechanism. The findings in XRD and DSC are in good agreement with conductivity results.     

Magnetocapacitance effect in Gd<Subscript> <Emphasis Type="Italic">x</Emphasis> </Subscript>Mn<Subscript>1–<Emphasis Type="Italic">x</Emphasis> </Subscript>S

The capacitance and dielectric loss tangent of Gd_xMn_1–xS (x ≤ 0.2) solid solutions have been measured at a frequency of 10 kHz without magnetic field and in a magnetic field of 8 kOe in the temperature range of 90–450 K. An increase in the permittivity and a dielectric loss maximum have been detected in the low-temperature region. It has been found that the temperature of the maximum of the imaginary part of the permittivity shifts to higher temperatures with increasing concentration. The magnetocapacitance effect has been revealed for two compositions. The dielectric loss has been described in the Debye model with “freezing” dipole moments and in the orbital-charge ordering model.     

On dielectrics of polymer electrolytes studied by impedance spectroscopy

We present a phenomenological view on dielectric relaxation in polymer electrolytes in the frequency range where conductivity is independent of frequency. Polymer electrolytes are seen as molecular mixtures of an organic polymer and an inorganic salt. The discussion applies also to ionic liquids. The following is based on systems with poly(ethylene oxide) (PEO) comprising the lithium perchlorate salt (LiClO₄) and also pure low-molecular PEO. In those systems, dipole-dipole interactions form an association/dissociation equilibrium which rules properties of the system in the low-frequency region. It turns out that effective concentration, c _S, of relaxing species provides a suitable variable for discussing electrochemical behavior of the electrolytes. Quantity c _S is proportional to the ratio of DC conductivity and mobility. Polymer salt mixtures form weak electrolytes. However, diffusion coefficient and corresponding molar conductivity display the typical (c _S)^1/2 dependence as well known from strong electrolytes, due to the low effective concentration c _S.     

Dielectric relaxation and ac conductivity of sodium tungsten phosphate glasses

Studies of dielectric relaxation and ac conductivity have been made on three samples of sodium tungsten phosphate glasses over a temperature range of 77–420 K. Complex relative permitivity data have been analyzed using dielectric modulus approach. Conductivity relaxation frequency increases with the increase of temperature. Activation energy for conductivity relaxation has also been evaluated. Measured ac conductivity (σ_m(ω)) has been found to be higher than σ_dc at low temperatures whereas at high temperature σ_m(ω) becomes equal to σ_dc at all frequencies. The ac conductivity obeys the relation σ_ac(ω)=Aω ^S over a considerable range of low temperatures. Values of exponent S are nearly equal to unity at about 78 K and the values decrease non-linearly with the increase of temperature. Values of the number density of states at Fermi level (N(E _F)) have been evaluated at 80 K assuming values of electron wave function decay constant α to be 0.5 (Å)^?1. Values of N(E _F) have the order 10²⁰ which are well within the range suggested for localized states. Present values of N(E _F) are smaller than those for tungsten phosphate glasses.     

NH<Subscript>4</Subscript>NO<Subscript>3</Subscript> as charge carrier contributor in glycerolized potato starch-methyl cellulose blend-based polymer electrolyte and the application in electrochemical double-layer capacitor

Potato starch (PS)-methyl cellulose (MC) blend solid biopolymer electrolytes infused with ammonium nitrate (NH₄NO₃) and glycerol as plasticizer are made via the solution cast technique. Fourier transform infrared (FTIR) spectroscopy indicates that NH₄NO₃ has interacted with the polymer blend host. The addition of 40 wt% glycerol in the highest conducting plasticizer free electrolyte has improved the conductivity to the order of ～10^?3 S cm^?1. The thermal stability of the electrolytes is identified by thermogravimetric analysis (TGA). Result from X-ray diffraction (XRD) analysis shows that the electrolyte with maximum conductivity value has the lowest degree of crystallinity. Differential scanning calorimetry (DSC) analysis reveals that the highest conducting plasticized electrolyte possesses the lowest glass transition temperature (T _g) of ?27.5 °C. Conductivity trend is further verified by dielectric analysis. Transference numbers of ion (t _ion) and electron (t _e) for the highest conducting electrolyte are identified to be 0.98 and 0.02, respectively, confirming that ions are the dominant charge carriers. Linear sweep voltammetry (LSV) evaluates that the potential window for the electrolyte is 1.88 V. The internal resistance of the electrochemical double-layer capacitor (EDLC) is between 29 and 64 Ω. From the charged-discharged measurement, the value of C _s is 31 F g^?1. The EDLC is stable over 1000 cycles.     

Dielectric,thermal, and electrochemical properties of PVC/PEMA blended polymer electrolytes complexed with zinc triflate salt

A new solid polymer electrolyte system based on poly (vinyl chloride) (PVC) and poly (ethyl methacrylate) (PEMA) containing zinc triflate [Zn(CF₃SO₃)₂] salt obtained in the form of thin film specimens using solution casting technique has been examined by means of complex impedance analysis, thermogravimetry (TG) and differential scanning calorimetric (DSC) studies, linear sweep voltammetry (LSV) and cyclic voltammetric (CV) measurements. The relevant mechanism of zinc ion transport involved in the case of the present polymer blend electrolyte viz., [PVC (30 wt%)/PEMA (70 wt%)] : x wt% [Zn(CF₃SO₃)₂] (where x = 10, 15, 20, 25, 30, and 35, respectively) has been evaluated in terms of AC impedance method, dielectric and electrical modulus formalisms. The optimized composition of the chosen blended polymer electrolyte system having 30 wt% loading of zinc triflate salt exhibited a single glass transition temperature (T _g) and possessed appreciable levels of thermal and electrochemical stability for possible utilization in zinc batteries.     

A study of optical absorption and dielectric properties in lithium chromium diphosphate compound

The optical properties of diphosphate LiCrP₂O₇ compound prepared by the classic ceramic method were recorded at room temperature. Absorption spectrum shows the presence of five characteristics bands related to the octahedral transitions of Cr³⁺ from ground term ⁴A_2g to excited terms. Crystal field strength and inter electronic repulsion Racah parameters were deduced. The calculated value of direct \( {E}_g^{\mathrm{direct}} \)=1.62 eV energy gap has been found using Tauc’s procedure. Besides, the dielectric properties were carried out by impedance spectroscopy at different temperatures (460–700 K). The frequency and temperature dependent of the real ε ^′ and imaginary ε ^″ parts of the dielectric constant were discussed. The variation of the frequency power law of the imaginary part of dielectric constant was analyzed in terms of two different conduction mechanisms. Furthermore, the modulus plots can be characterized by the empirical Kohlrausch–Williams–Watts (K.W.W.) function and the obtained values of activation energies deduced from relaxation frequency are in order of E _a (I) = 0.49 eV and E _a (II) = 0.87 eV.

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Graphical abstract Optical and dielectric proprieties of lithium chromium diphosphate