Tauc Method Research Articles

The impact of sintering temperature on structural properties, optical and dielectric parameters under photon energy of Ni0.6Cd0.4FeAl0.5Cu0.5O4 for optoelectronic devices

The impact of calcination temperature on the structural and optical properties of Ni0.6Cd0.4FeAl0.5Cu0.5O4 spinel ferrites was investigated in this work. These samples were prepared using sol-gel method and sintered at two different temperatures (950 °C and 850 °C). The X-ray diffraction analysis and Rietveld refinement confirm that the sample were well crystallized in the cubic spinel structure (Fd3¯m space group). With increasing sintering temperature, unit cell parameters and crystallites size show an increasing trend. The values of optical band-gap energy were calculated using absorbance, reflectance, and Tauc's method. These measurements confirm the direct optical transitions for the prepared samples. The direct bandgap energy calculated, respectively for S950 and S850 are EgTau = 2.6 eV, EgTau = 2.41 eV, EgDRS = 2.41 eV and 2.39, EgdrivAbso = 2.45 eV and 2.47 eV and EgdrivRefel = 2.382 eV and 2.377 eV. This shift of Eg value between Tauc method, spectra diffuse reflectance spectroscopy (DRS) is related to the lack of precision of Tauc method. Furthermore, the obtained low Urbach energies confirm the high quality of the prepared samples and imply that the degree of disorder and defects decreases as the sintering temperature rises. The Cauchy parameters were determined from the variation of the refractive index. In the other hand, the dispersion energy parameters were evaluated from the Wemple–Didomenico relation. The variations with wavelength of optical constants such as penetration depth, extinction coefficient, conductivity, and dielectric constants have also investigated. The low dielectric value and the relatively small bandgap energy show that this compound can be proposed as a good candidate for optical and optoelectronic applications.

Optical properties investigation of Sr2CaFe2WO9 triple perovskite for optoelectronic applications

In this manuscript, Sr2CaFe2WO9 triple perovskite, in a powder state, has been studied in the context of these linear and nonlinear optical properties. This material was developed as a powder with a polycrystalline structure by a solid-state reaction. These optical properties were measured from transmittance and absorbance for wavelengths between 250 and 850 nm, using a UV-Visible spectroscopy at room temperature. The analysis of the optical results showed the possibility of using Sr2CaFe2WO9 in optoelectronic technology due to its optical properties suitable for this field. The transmittance and absorbance, absorption coefficient, band gap (Eg), Urbach energy, refractive index, optical conductivity, and dielectric function were investigated. The gap energy of the sample determined by the Tauc method is 3.06 eV, while the derivation of the absorption spectrum fitting (DASF) method showed that the studied material has a direct bandgap. The first and third-order nonlinear susceptibilities, as well as the static and nonlinear refractive indices, were also calculated for the studied powder. Sr2CaFe2WO9 can be exploited as a promising material for upgraded applications in optoelectronic applications, given its optical properties either linear or nonlinear.

Study of optical and photoelectric properties of copper oxide films

In this work, the dependence of the phase state, photosensitivity region, band structure, and optical quality of 3D-printed nanostructured copper oxide films on the annealing temperature (Ta) was investigated. It was established that both as-deposited and annealed copper oxide films at Ta ≤ 400 °C have the CuO phase and the films annealed at Ta = 450 °C correspond to the Cu2O phase. A possible mechanism of convertation of two phases is discussed. It was established that the band gap of CuO films, caused by indirect allowed optical transitions, determined by the absorption coefficient first derivative and Tauc methods, corresponds to 1.60 eV and 1.35 eV, respectively. It was established that the optical quality of CuO films is the best at Ta = 350 °C. The obtained results open the way to obtain a material suitable for modern optoelectronic applications, in particular, for the development of environmentally friendly solar cells.

Graphene Oxide Incorporated Zinc Oxide Thin Films by Spray Pyrolysis for Efficient Photodegradation of Methylene Blue

AbstractPhotodegradation of methylene blue dye was studied with pure and graphene oxide incorporated zinc oxide thin films as catalysts. Graphene oxide content in the precursor solution was varied from 0.0005 to 0.005 g/L. Thin films were prepared by automated spray pyrolysis technique at a substrate temperature of 425 °C. Structural studies revealed the formation of hexagonal wurtzite structure of zinc oxide. Carbon presence in the films was confirmed with energy‐dispersive spectroscopy. Optical band gap of the samples was determined using Tauc method. Intensity of the near band emission of photoluminescence spectrum was found to decrease upon increasing graphene oxide concentration. Photocatalytic activity of all the films has been studied against methylene blue dye under solar irradiation for 180 minutes and it is found that the highest graphene oxide content attributes to better degradation efficiency of 91.2 %.

Synthesis and DC Electrical Conductivity of Nanocomposites Based on Poly(1-vinyl-1,2,4-triazole) and Thermoelectric Tellurium Nanoparticles.

In this work, the structural characteristics and DC electrical conductivity of firstly synthesized organic-inorganic nanocomposites of thermoelectric Te0 nanoparticles (1.4, 2.8, 4.3 wt%) and poly(1-vinyl-1,2,4-triazole) (PVT) were analyzed. The composites were characterized by high-resolution transmission electron microscopy, X-ray diffractometry, UV-Vis spectroscopy, and dynamic light scattering analysis. The study results showed that the nanocomposite nanoparticles distributed in the polymer matrix had a shape close to spherical and an average size of 4-18 nm. The average size of the nanoparticles was determined using the Brus model relation. The optical band gap applied in the model was determined on the basis of UV-Vis data by the Tauc method and the 10% absorption method. The values obtained varied between 2.9 and 5.1 nm. These values are in good agreement with the values of the nanoparticle size, which are typical for their fractions presented in the nanocomposite. The characteristic sizes of the nanoparticles in the fractions obtained from the Pesika size distribution data were 4.6, 4.9, and 5.0 nm for the nanocomposites with percentages of 1.4, 2.8, and 4.3%, respectively. The DC electrical conductivity of the nanocomposites was measured by a two-probe method in the temperature range of 25-80 °C. It was found that the formation of an inorganic nanophase in the PVT polymer as well as an increase in the average size of nanoparticles led to an increase in the DC conductivity over the entire temperature range. The results revealed that the DC electrical conductivity of nanocomposites with a Tellurium content of 2.8, 4.3 wt% at 80 °C becomes higher than the conventional boundary of 10-10 S/cm separating dielectrics and semiconductors.

Diffuse reflectance spectroscopy of solid solutions in the Ag7PS6-Ag8GeS6 system

Samples of Ag7+x(P1–xGex)S6 (x = 0, 0.1, 0.25, 0.33, 0.5, 0.75, 1.0) solid solutions were obtained in the form of microcrystalline powders by grinding in an agate mortar. The diffuse reflectance spectra of the obtained Ag7+x(P1–xGex)S6 samples were studied in the spectral range 200 to 1400 nm at 293 K. The spectral dependences were analyzed using multilevel approximation by applying the Kubelka–Munk function and the Tauc method. It has been found that for Ag7+x(P1 xGex)S6 solid solutions, a red shift of the reflection edge beginning is observed with increasing the Ge content. The pseudo-gap values of Ag7+x(P1–xGex)S6 solid solutions was estimated by the Tauc method. It was found that the heterovalent cationic substitution P+5 → Ge+4 within the anionic sublattice leads to a monotonic nonlinear decrease in the pseudo-gap values.

First-principle study of the optoelectronic properties of GaxIn1-xBiyP1-y quaternary alloys lattice-matched to InP for telecommunication applications

In this work, we present a theoretical investigation of the structural and optoelectronic properties of GaxIn1-xBiyP1-y quaternary alloys lattice-matched to InP using the full-potential linearized augmented plane wave approach based on the functional theory of density. The local density approximation (LDA) and the generalized gradient approximation of Wu–Cohen (WC-GGA) have been used for calculating the structural properties of GaxIn1-xBiyP1-y quaternaries. The lattice matching condition and the range of ( x, y) concentrations for which the quaternary alloys are lattice-matched to InP substrate were determined. It is found that the calculated lattice constants of GaxIn1-xBiyP1-y for all selected concentrations ( x, y) are about 5.9 Å, which are in good agreement with the experimental value of the lattice constant of InP (5.869 Å). The electronic property calculations are executed via EV-GGA and TB-mBJ approximations. The calculated band structures show that GaxIn1-xBiyP1-y quaternaries have semiconductor character and exhibit a direct band gap, for all selected concentrations ( x, y). In addition, the optical properties were calculated and discussed in detail. And also, the optical band gaps of quaternaries were determined using Tauc's method. We observed that the GaxIn1-xBiyP1-y quaternaries cover the wavelength ranging from 0.911 to 2.456 µm while maintaining a lattice match to the InP substrate. The obtained results reveal that these quaternaries are suitable candidates for telecommunication applications.

Enhancement of the photocatalytic activity of fabricated ZnS nanoparticles in the photodegradation of methylene blue

This paper first aims to synthesize and characterize ZnS nanoparticles (NPs) by the hydrothermal method. The synthesized NPs are investigated by x-ray diffraction (XRD), field emission electron microscopy (FE-SEM), energy-dispersive x-ray spectroscopy (EDX), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR), ultraviolet-visible (UV–vis) spectroscopy, N2 adsorption-desorption, diffuse reflectance spectroscopy (DRS). Thiosemicarbazide/Zinc acetate dehydrate/ Ethylenediamine/Deionized water are utilized as precursors with three molar ratios and labeled as S1 = 2:1:1:1, S2 = 2:1:1:3 and S3 = 1:2:2:2, respectively. The synthesized pure ZnS NPs under UV irradiation present a higher photodegradation rate in comparison with the existing pure and doped ZnS-based ZnS. The direct optical bandgap of S1, S2 and S3 are estimated by the DRS method and approved by the Tauc method as 3.29 eV, 3.38 eV and 3.37 eV, respectively. The photocatalytic activities of the synthesized pure NPs (S1, S2 and S3) are calculated to be 0.044, 0.036 and 0.050 min−1, respectively. The results indicate the significant effect of precursors on the crystallite phase, optical bandgap and photocatalytic activity of the ZnS NPs so that in comparison with other studies, they could be an effective candidate in the field of photodegradation of the organic dyes.

Physical and optical properties of ternary lead-bismuth tellurite glass

A series of six lead-bismuth tellurite glass samples were prepared by using the melt quenching technique. The Physical properties of the samples such as density and molar were studied. The measurements of density were calculated via using Archimedes' principle. XDR technique was used to confirm the amorphous nature of the samples. The optical properties of the samples such as direct and indirect bandgaps were calculated based on the Davis-Mott equation by employing Tauc's method. The disorderliness of the glass system was measured by calculating Urbach energy and steepness. Density and refractive indices results show an increasing trend with increasing PbO concentration. The non-metallic nature of the samples was investigated by using the metallization criterion. Optical basicity and basicity moderating parameters were calculated for each glass sample by using Duffy and Ingram formula. The metallization criterion results of the synthesized glasses are best for nonlinear optical devices.

PREPARATION AND PROPERTIES OF CERAMIC MATERIALS IN THE Ag6PS5I‒Ag7GeS5I SYSTEM

This work is devoted to the preparation of dense Ag+ conductive ceramic solid electrolytes in the Ag6PS5I‒Ag7GeS5I system and to the study of their electrical and optical properties. Using the non-destructive and simple method of optical diffuse reflectance spectroscopy, the value of the optical pseudogap energy of the Ag6+x(P1-xGex)S5I (x=0, 0.25, 0.5, 0.75, 1.0) solid solutions was obtained using the Kubelka-Munk function with the application of Tauc's graphic method. As a result of the performed mathematical analysis and graphic processing, it was established that the quaternary chalcohalogenides Ag6PS5I, Ag7GeS5I and solid solutions Ag6+x(P1-xGex)S5I (x=0.25, 0.5, 0.75) belong to direct-band semiconductors characterized by a forbidden optical transition . The study of electrical conductivity of Ag6+x(P1-xGex)S5I solid solutions (x=0, 0.25, 0.5, 0.75, 1.0) was carried out by the method of impedance spectroscopy, in the frequency 1×101–3×105 Hz and temperature 293–383 K ranges. For all ceramic materials prepared on the basis of Ag6+x(P1-xGex)S5I (x=0, 0.25, 0.5, 0.75, 1.0) solid solutions, an increase in the values of total electrical conductivity was observed, which is characteristic of materials with ionic electrical conductivity in the solid state.
 Keywords: argyrodites; solid solutions; ceramic; impedance spectroscopy; conductivity; optical properties; optical pseudogap.

Growth and temperature-tuned band gap characteristics of LiGd(MoO4)2 single crystals for optoelectronic applications

LiGd(MoO4)2 has been investigated due to its optoelectronic applications, especially for development of light-emitting diodes. In the present paper, LiGd(MoO4)2 single crystals grown by Czochralski method was studied in terms of structural and temperature dependent optical properties. X-ray diffraction analysis showed that the crystal crystallizes in a single phase tetragonal structure. Raman spectrum exhibited six distinguishable peaks around 207, 319, 397, 706, 756 and 890 cm−1. These peaks correspond to vibrational modes of free rotation, symmetrical stretching, symmetric bending, antisymmetric stretching and antisymmetric bending of (MoO4)2− tetrahedron. Infrared transmittance spectrum had eight minima around 2114, 2350, 2451, 2854, 2929, 2960, 3545 and 3578 cm−1 which are due to multiphonon absorptions. Spectral change of transmittance curves at various temperature between 10 and 300 K was utilized to elucidate temperature effect on absorption characteristics. Optical band gap of the material was found using Tauc and spectral derivative methods. The band gap value was obtained as 3.09 eV at room temperature and this value increased to 3.22 eV with decreasing temperature down to 10 K. The detailed analysis on the temperature dependency of the band gap was applied by Varshni model. The band gap at 0 K and change of rate of the band gap were estimated as 3.23 eV and −1.45 × 10−3 eV/K, respectively. Room temperature photoluminescence spectrum of the crystal presented a peak around 709 nm which corresponds to red light emission. LiGd(MoO4)2 is a potential candidate for optoelectronic devices emitting red light.

Indium and hafnium chloride modified titanium oxide thin films

Titanium oxide (TiO2) thin films were prepared by the sol-gel spin-coating technique. The influences of indium (In), hafnium (Hf), and In&Hf doping on electrochemical and structural properties were investigated. The structural properties of undoped and doped TiO2 were investigated using thermogravimetric/differential thermal (TG/DTA), X-ray Powder Diffraction (XRD), and atomic force microscopy (AFM). The optical properties were investigated using ultraviolet–visible (UV–Vis) spectroscopy, and band gap energies were calculated using the Tauc method from transmission measurement. The results showed that TiO2 had better electrochemical properties, and the band gap increased with In&Hf doping.

Electrical, optical and dielectric properties of polyvinylpyrrolidone/graphene nanoplatelet nanocomposites

In this study, polyvinylpyrrolidone (PVP) nanocomposite films containing GnP in four different volume fractions (φ = 0.00, 2.00, 4.08, and 5.91) were prepared by the solution casting method. UV–Vis absorbance spectroscopy, reflectance spectroscopy, and two-point probe resistivity measurement techniques were used to examine the optical, electrical, and dielectric properties of these films. Optical band gap energies of the PVP/GnP nanocomposites were obtained using the most commonly used Tauc, Kubelka-Munk (K-M), Absorbance Spectrum Fitting (ASF), and Derivative (DM) methods. The results obtained by Tauc, K-M, and ASF methods were found to be consistent with each other. In addition, basic optical parameters such as Urbach energy (Eu), refractive index (n), optical conductivity (σopt) and dielectric constant (ε) of the PVP/GnP nanocomposites were investigated. As the GnP volume fraction increased in the nanocomposites, the electrical conductivity, Eu, n, σopt and ε increased whereas Eg decreased. These nanocomposites produced by varying the GnP volume fraction are promising for using optics, electricity, optoelectronics, and many other industrial applications.

Impact of Sm3+ ions on structural, thermal, optical and photoluminescence properties of ZnO–Na2O–PbO–B2O3 glasses for optoelectronics device applications

This work describes the impact of trivalent samarium (Sm3+) ions concentrations on the thermal, structural, physical, optical and photoluminescence (PL) characteristics in Zinc Sodium Lead Borate (ZnNaPbB) glasses with configuration (70-x) B2O3–10PbO–10ZnO–10Na2CO3-xSm2O3, (where x = 0.1–2.0 mol%). The glass samples were synthesized using a traditional melt-quench technique and characterized by various spectroscopic methods such as X-ray diffraction (XRD), Raman spectroscopy, Fourier Transform Infrared (FT-IR), UV–Vis–NIR spectra, Differential scanning calorimetry (DSC) and PL emission-excitation spectra to illuminate their photonic applications. The broad band perceived in the XRD diffractogram confirmed the amorphous nature of an un-doped ZnNaPbB glass. The physical properties including thickness, density, molar volume, dielectric constant, rare earth (RE) ion concentration, field strength and molecular electronic polarizability, etc. were calculated from the standard formulae. The FT-IR spectra identify the presence of stretching vibration in BO3 and BO4 units with some additional structural and functional groups with their bond nature. The observed DSC data was used to estimate the glass transition temperature (Tg). The absorption spectra presented all the probable transitions of Sm3+ ion-doped ZnNaPbB glass and the optical band gaps were computed using Tauc's method. All the glass samples depicted band gap values over 3 eV, proving that the material is insulating. The absorption spectra were utilized to evaluate Judd-Ofelt (J-O) parameters which were further used in different radiative parameters calculations to find the luminous levels of Sm3+ ions doped ZnNaPbB glasses. The PL emission spectra of the present ZnNaPbBSm glasses parade four bands parallel to the transitions 4G5/2 to 6H5/2 (563 nm), 6H7/2 (599 nm), 6H9/2 (646 nm) and 6H11/2 (706 nm), respectively. Additionally, the evaluated values of the emission cross-section and branching ratios describe the suitability of the present ZnNaPbBSm glasses for optoelectronic applications. Further, the colorimetric parameters such as CIE coordinates (x, y) and correlated color temperature (CCT) were evaluated using PL emission data and the measured CIE coordinates are found in the reddish-orange region for the present glasses. The time decay profiles of as-prepared glasses were used to evaluate the experimental lifetime, energy transfer parameter and type of donor-acceptor interaction. The Dexter theory and Inokuti-Hirayama (I–H) fitting are used to recognize the type of interaction in non-radiative energy transfer which is responsible for the concentration quenching. The result demonstrates that the as-prepared ZnNaPbBSm glasses are applicable for optoelectronics device applications.

Optical characteristics of silver-based nano-composites fabricated by an environmentally friendly method

This work presents a simple and environmentally friendly method of synthesis of chitosan and Ag nanocomposites. The structure of the obtained organic matrix was determined by Fourier-transform infrared spectroscopy (FTIR). Formation of chitosan- chitin copolymer was discovered. Nanocomposite films with silver content of 9–71 wt.% were prepared. The microstructure and elemental composition of the obtained films were investigated by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The prepared films are characterized by uniform distribution of silver nanoparticles in the organic matrix. Optical properties were studied by diffuse reflectance spectroscopy. The diffuse reflectance spectra of the films have maxima. The increase of the Ag 0 concentration in the nanocomposite films was found to lead to the maximum shift of the diffuse reflectance spectra to longer wavelengths. The optical transitions energies were estimated using the Kubelka–Munk function in combination with the Tauc method.

A spectroscopic study and the effect of gamma rays on the stability and efficiency of boron subphthalocyanine dye for solar energy applications

Gamma irradiation with different doses (0.0, 10, 20, 30, 40 and 50 kGy) effects on the structural and optical features of organic boron subphthalocyanine (SubPc-Cl) thin films are studied. The main characteristic peaks and stability of SubPc-Cl dye under γ-ray exposure with different doses were recognized by using Fourier transform infrared spectroscopy (FTIR). The surface composition of the SubPC-Cl thin films under γ-ray exposure with different doses (0.0 & 50 kGy) was recognized by using X-ray photoelectron spectroscopy (XPS). X-ray diffraction (XRD), Field emission scanning electron microscopy (FE-SEM) and High-resolution transmission electron microscopy (HR-TEM) results were applied to determine the crystal structure and morphology of the SubPC-Cl thin films under γ-ray exposure with different doses. Various approaches such as the first derivation of the absorption spectrum fitting (DASF), Tauc's method, Drude model and the single-effective-oscillator model were discussed to obtain the optical properties of SubPc-Cl) thin films under γ-ray exposure with different doses. Such investigation can add to the growth of subphthalocyanine applications such as photovoltaic or dosimetry applications.

Rutile TiO2 thin films growth on glass substrates with generation of high entropy interface

TiO2 thin films obtained through Reactive Magnetron Sputtering (RMS) have been extensively studied in the last decades for several applications as photocatalyst and self-cleaning coats. However, reactive deposition through MS onto large area substrates can be troublesome due to inhomogeneous films thickness and poor adhesion between film and substrate. This paper investigates the deposition of TiO2 thin films on glass substrates through a two steps method, namely: 1- deposition of nanometer thickness Ti metallic films on glass substrate, through triode magnetron sputtering; 2- oxidation of the Ti film through thermal treatment in atmospheric air, to obtain stoichiometric TiO2 layers. The film oxidation was performed concomitantly to the glass thermal treatment carried out at 650 °C. Analysis through XPS depth profile indicates the formation of a chemically graded high entropy interlayer due to the interdiffusion of atoms from substrate to film and vice-versa, during the thermal treatment. The high entropy interface layer contributes to reduces the mismatch between the film and the substrate lattice, resulting in an improvement of film adhesion. The badgap analysis through Tauc method show two energy values, namely 3.2 eV and 2.9 eV, which can be attributed to TiO2-rutile layer and the high entropy zone at interface, composed by [Ca-Na-Si-Ti]Ox oxides. The wettability results show that the contact angle may be as low as 10° between a deionized water drop and the rutile-TiO2 surface, after activation with UV light irradiation, which is characteristic of super-hydrophilic surface.

Study of the oxidation process of bismuth nanoparticles using NaClO

Bismuth nanoparticles (NPs) colloids synthesized in deionized water by laser ablation of solids in liquids technique (LASL) were oxidized using NaClO solutions at different concentrations. Oxidized nanomaterials were characterized using several techniques. The crystalline phases of the bismuth compound were determined using Raman microspectroscopy, and the crystallographic structure was identified by x-ray diffraction (XRD). The size and morphology of the obtained nanomaterials were studied by transmission electron microscopy (TEM). The chemical states were determined using x-ray photoelectron spectroscopy (XPS), and the optical properties of the colloids were characterized by UV–vis spectroscopy. The absorption spectra were analyzed using the Tauc method to determine the band gaps of the obtained nanomaterials. Our results showed morphological changes, starting from small nanoparticles to nanosheets and a mixture of nanosheets with hollow nanoparticles. Two kinds of nanomaterials were found depending on the NaClO solution concentration: Bi2O2CO3 single phase and a mixture of δ-Bi2O3 and Bi2O2CO3. Some samples were tested as photocatalysts and showed good performance in the degradation of methylene blue in solution. To the best of our knowledge, this is the first study on the oxidation process of bismuth colloidal nanoparticles at room temperature.

Zinc Oxide Films Fabricated via Sol-Gel Method and Dip-Coating Technique-Effect of Sol Aging on Optical Properties, Morphology and Photocatalytic Activity.

Zinc oxide layers on soda-lime glass substrates were fabricated using the sol-gel method and the dip-coating technique. Zinc acetate dihydrate was applied as the precursor, while diethanolamine as the stabilizing agent. This study aimed to determine what effect has the duration of the sol aging process on the properties of fabricated ZnO films. Investigations were carried out with the sol that was aged during the period from 2 to 64 days. The sol was studied using the dynamic light scattering method to determine its distribution of molecule size. The properties of ZnO layers were studied using the following methods: scanning electron microscopy, atomic force microscopy, transmission and reflection spectroscopy in the UV-Vis range, and the goniometric method for determination of the water contact angle. Furthermore, photocatalytic properties of ZnO layers were studied by the observation and quantification of the methylene blue dye degradation in an aqueous solution under UV illumination. Our studies showed that ZnO layers have grain structure, and their physical-chemical properties depend on the duration of aging. The strongest photocatalytic activity was observed for layers produced from the sol that was aged over 30 days. These layers have also the greatest porosity (37.1%) and the largest water contact angle (68.53°). Our studies have also shown that there are two absorption bands in studied ZnO layers, and values of optical energy band gaps determined from positions of maxima in reflectance characteristics are equal to those determined using the Tauc method. Optical energy band gaps of the ZnO layer fabricated from the sol aged over 30 days are EgI = 4.485 eV and EgII = 3.300 eV for the first and second bands, respectively. This layer also showed the highest photocatalytic activity, causing the pollution to degrade 79.5% after 120 min of UV irradiation. We believe that ZnO layers presented here, thanks to their attractive photocatalytic properties, may find application in environmental protection for the degradation of organic pollutants.

“Synthesis, structural, optical and dielectric characterization of new pyrochlore solid solution B1.5Sb1.5Zn1-xCuxO7″

A new pyrochlore solid solution with formula B1.5Sb1.5Zn1-xCuxO7 has been synthesized at high temperature with ceramic method at 1000 ​°C. A linear decrease of the cell parameter was observed according to the zinc concentration decrease on B and A sites. Rietveld refinement of the compounds Bi1.5Sb1.5Zn1-xCuxO7 for x ​= ​0, x ​= ​0.5 and x ​= ​1 by means of X-ray powder diffraction analysis confirmed an overall A2B2O7 cubic pyrochlore structure and Fd-3m symmetry. The reliability factors are respectively RBrag: 1.97; 4.31; 3.93 and Rf: 2.19; 4.15; 4.92. The UV-diffuse measurement shows absorbance evolution between UV and visible domain. Energy band gap calculated by the Tauc method leads to values between 3.15 ​eV for the fraction x ​= ​0 and 1.84eV for the fraction x ​= ​1. A regular decrease is observed between the two values. Dielectric properties as a function of temperature show an increase in electrical conductivity with copper content.