Tailoring of optical band gap and electrical conductivity in a-axis oriented Ni doped Chromium Oxide thin films

Ni doped Cr₂O₃ (NCO) films have attracted much attention due to their applications in the field of photovoltaics. This study reports the tailoring of structural, electrical and optical properties as a function of Ni doping in Chromium oxide (Cr₂O₃). NCO thin films were grown by Pulsed laser deposition (PLD) using 2nd harmonic Nd:YAG Laser on n-Si (100) with in-situ annealing of 450?°C. Structural analyses based on X-ray diffractometry (XRD) and Raman Spectroscopy showed the inconsistent variation in crystallinity and shift in $A_{1g}$ band in turn revealing the successful incorporation of Ni into Chromium oxide host lattice. In addition, electrical measurements also showed an inconsistent variation in resistivity ranging from 10² to 10⁴$\Omega ?\mathit{cm}$. The properties showed widening of band gap energy (E_g) from 3.41 to 3.60?eV as a function of Ni doping concentration with significantly decreased reflectance in the range of 500–600?nm thereby increasing the absorption, a pre-requisite for solar absorbers.     

Synthesis and characterization of novel polyphenol species derived from bis(4‐aminophenyl)ether: Substituent effects on thermal behavior,electrical conductivity,solubility, and optical band gap

In this study, four different Schiff bases namely 4,4′‐oxybis[N‐(2‐hydroxybenzilidene)aniline] (2‐HBA), 4,4′‐oxybis[N‐(4‐hydroxybenzilidene)aniline] (4‐HBA), 4,4′‐oxybis[N‐(3,4‐dihydroxybenzilidene)aniline] (3,4‐HBA), and 4,4′‐oxybis[N‐(4‐hydroxy‐3‐methoxybenzilidene)aniline] (HMBA) were synthesized. These Schiff bases were converted to their polymers that have generate names of poly‐4,4′‐oxybis[N‐(2‐hydroxybenzilidene)aniline] (P‐2‐HBA), poly‐4,4′‐oxybis[N‐(4‐hydroxybenzilidene)aniline] (P‐4‐HBA), poly‐4,4′‐oxybis[N‐(3,4‐dihydroxybenzilidene)aniline] (P‐3,4‐HBA), and poly‐4,4′‐oxybis[N‐(4‐hydroxy‐3‐methoxybenzilidene)aniline] (PHMBA) via oxidative polycondensation reaction by using NaOCl as the oxidant. Four different metal complexes were also synthesized from 2‐HBA and P‐2‐HBA. The structures of the compounds were confirmed by FTIR, UV‐vis, ¹H and ¹³C NMR analyses. According to ¹H NMR spectra, the polymerization of the 2‐HBA and 4‐HBA largely maintained with C? O? C coupling, whereas the polymerization of the 3,4‐HBA and HMBA largely maintained with C? C coupling. The characterization was made by TG‐DTA, size exclusion chromatography and solubility tests. Also, electrical conductivity of the polymers and the metal complex compounds were measured, showing that the synthesized polymers are semiconductors and their conductivities can be increased highly via doping with iodine ions (except PHMBA). According to UV–vis measurements, the optical band gaps (E_g) were found to be 3.15, 2.06, 3.23, 3.02, 2.61, 2.47, 2.64, 2.42, 2.83, 2.77, 2.78, and 2.78 for 2‐HBA, P‐2‐HBA, 4‐HBA, P‐4‐HBA, 3,4‐HBA, P‐3,4‐HBA, HMBA, PHMBA, 2‐HBA‐Cu, 2‐HBA‐Co, P‐2‐HBA‐Cu, and P‐2‐HBA‐Co, respectively. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Influence of Al2O3 on the electrical conductivity and structure of calcium-silicate-based melts

Electrical conductivity and structure of the CaO-SiO₂-based mold flux melts with various Al₂O₃ contents were investigated. The results show that the electrical conductivity increases with the addition of Al₂O₃ from 2 wt% to 4 wt%, but decreases with the further increase of Al₂O₃ from 4 wt% to 8 wt%. Correspondingly, the apparent activation energy reduces firstly from 55.12 ± 1.20 kJ mol to 41.09± 0.38 kJ mol, and then increases from 41.09 ± 0.38 kJ mol to 98.99 ± 1.42 kJ mol. The structure analyses suggest that complex structural units, such as Si-O-Al, Al-O⁰, Si-O-Si and Q³(Si), reduce first, but increase with the further addition of Al₂O₃. Conversely, these simple structural units, such as Al-O^-, Q⁰(Si), Q¹(Si) and Q²(Si) vary in the opposite way with the change of Al₂O₃ content. From the variations of electrical conductivity, activation energy and structural units, it can be found that when Al₂O₃ works as network breaker to simplify the melt structure, the energy barrier for transportation of conducting ions/ionic reduce, which results in the increase of electrical conductivity; while when Al₂O₃ becomes into network former, the conductivity increases, correspondingly.     

Heat treatment effects on the structural and optical properties of thin Bi2(Se1-xTex)3 films

Thin layers of Bi₂-chalcogenides, in the form of Bi₂(Se_1-xTe_x)₃ films, were evaporated on glass substrates by means of the vacuum thermal evaporation. Microstructure of the as prepared layers was investigated by x-ray diffraction (XRD) analysis. Identifications of the surface morphology and roughness were determined via scanning electron microscope (SEM). Optical transmissivity spectra proved that the as prepared films have low transparency with growing trend upon increasing the wavelength beyond the infra-red region. Low transmittance was observed for the as prepared films. Heat treatment, in the form of temperature annealing, was carried out aiming at boosting the structural features and the materials transmissivity. Structural properties and surface features of the annealed films were probed also via XRD and SEM analyses. It was found that the crystal size increases while the micro-strain and the dislocation density decrease obviously due to annealing. It was also observed that the annealing process significantly enhances the materials transmission especially in the range of higher wavelengths. Optical band gap was studied after annealing at various temperatures. Notable change in the band gap value was observed as a result of annealing. The band gap of the undoped (Bi₂Se₃) materials showed significant rise from 0.14 to 1.79 eV due to annealing. Similarly, the Te-doped samples exhibited notable increase in their band gap values after annealing. For example, the optical band gap of the sample doped at x = 0.20 increased from 0.03 to 0.41 eV by annealing. On the other hand, transmittance was also enhanced by annealing. For samples treated at 250 °C for 3 h, their optical transmissivity is enhanced to over 99% at the visible near-IR range. Such significant enhancement can be ascribed to structural enhancements. With such enhancement in the optical transmissivity, optoelectronic applications including transparent electrode can be met.     

Influence of Al3+ on the cross relaxation process and electrical properties of Dy3+ activated Gd2O3 phosphor for white LED application

Gd₂O₃:Dy³⁺ Al³⁺ phosphors is synthesised by a wet-chemical method for various concentrations of Al³⁺ ion. X-ray diffraction, photoluminescence and impedance spectroscopy are used to understand the physio-chemical properties of the phosphors. The emission spectra of Dy³⁺ ion exhibit transition peaks centred at 572 nm (yellow), 486 nm (blue) and 669 nm (red). Energy transfer from Gd³⁺ to Dy³⁺ is also verified by exciting the phosphors at 274 nm. Some of the Dy³⁺ ions occupy both C₂ and S₆ site of Gd³⁺ ion in Gd₂O₃ matrix. It is also revealed that the enhancement of Dy³⁺ emission is strongly correlated to the surface morphology of the phosphors. Introducing Al³⁺ ions in Gd₂O₃:Dy³⁺ phosphor affect the emission properties of Dy³⁺ ions and its influence is explored at various concentration of Al³⁺ ions. The energy level diagram is presented to explain the cross-relaxation process among Dy³⁺ ions and the energy transfer from Gd³⁺ to Dy³⁺ ion.     

Structural,electrical, and linear/nonlinear optical characteristics of thermally evaporated molybdenum oxide thin films

Homogeneous thin films of Molybdenum oxide (MoO₃) were grown on quartz and glass substrates using the thermal evaporation method. XRD results showed that the MoO₃ powder has a polycrystalline structure with an orthorhombic crystal system whereas the MoO₃ thin films have amorphous nature. SEM images showed that the MoO₃ thin films have a nearly uniform surfaces with worm-like shape grains. The film thickness influences on the linear and nonlinear optical characteristics of MoO₃ thin films that were examined using spectrophotometric measurements and from which, the linear optical constants of the MoO₃ thin films were estimated. The electronic transition type was determined as a direct allowed one. The values of the optical band gap were obtained to be in the range of 3.88–3.72 eV. The dispersion parameters, third-order nonlinear optical susceptibility, and the nonlinear refractive index of the MoO₃ thin films were determined and interpreted in the light of the single oscillator model. The temperature dependence of the DC electrical conductivity and the corresponding conduction mechanism for the MoO₃ films were investigated at temperatures ranging from 303 to 463 K.     

PP/Al(OH)_3/Mg(OH)_2复合材料的导热性能

制备了PP（聚丙烯）/Al(OH)₃/Mg(OH)₂导热复合材料,并用稳态平板导热系数测试仪在不同测试温度下测定该复合材料的导热系数。结果表明,加入Al(OH)₃和Mg(OH)₂使PP导热系数提高。复合材料的导热系数随着填料含量的增加而非线性提高,随着测试温度的升高而非线性提高,随着填料粒径的增大而非线性增大。     

Investigation of the electrical conductivity of sintered monoclinic zirconia (ZrO2)

High-density monoclinic ZrO₂ was manufactured through sintering at ~1200 °C by using nanosized powders. Then, the electrical conductivity was measured at a range of high temperatures (700–900 °C) by electrical impedance spectroscopy (EIS). For the as-sintered monoclinic ZrO₂, the measured electrical conductivity was 3.2×10⁻⁵ s/cm (for 80% TD) and 4.4×10⁻⁵ s/cm (for 89% TD) at 900 °C. After aging at 900 °C for 100 h, the electrical conductivity of the monoclinic ZrO₂ of 80%-TD decreased by more than 50%. However, after reheating at 1200 °C for 1 h, approximately 80% of the conductivity was recovered compared to the value of the as-sintered monoclinic ZrO₂. The pure monoclinic crystal structure was retained despite the aging and reheating treatment. Based on microstructural observations of the aged and reheated monoclinic ZrO₂, the changes in electrical conductivity after aging and reheating were explained by the formation and recovery of micro-cracks, respectively.     

Synthesis and electrical conductivity of La-Sr-X-Mg-O (X = Ti, Zr, Al) perovskite solid solution

Perovskite solid solutions of (La_0.6Sr_0.4)(X_1−yMg_y)O_3−δ (X = Ti, Zr, Al) were prepared by a coprecipitation method using corresponding aqueous solutions and ammonium carbonate solution. The freeze-dried powders were sintered in air at 1000-1500 °C for 1-36 h. Single phase solid solutions were produced in the compositions of (La_0.6Sr_0.4)(Zr_0.6Mg_0.4)O_3−δ and (La_0.6Sr_0.4)(Al_0.9Mg_0.1)O_3−δ where (3 − δ) < 3. For the compositions of X = Ti and Zr for y = 0.1 where (3 − δ) > 3, two phases including perovskite solid solution were produced at 1400-1500 °C. The stability of perovskite solid solution was closely related to the fraction of lattice oxygen atom (3 − δ). A relatively high conductivity was measured for (La_0.6Sr_0.4)(Al_0.9Mg_0.1)O_3−δ (σ = 4.15 × 10⁻⁴ S/cm at 600 °C, activation energy 113.4 kJ/mol). The influence of fraction of oxide ion vacancy on the activation energy was small for δ = 0.1-0.3 of perovskite solid solution.     

Effect of Au ion beam on structural,surface, optical and electrical properties of ZnO thin films prepared by RF sputtering

In the present work, ZnO thin films were irradiated with 700?keV Au⁺ ions at different fluence (1?× 10¹³, 1?× 10¹⁴, 2?× 10¹⁴ and 5?× 10¹⁴ ions/cm²). The structural, morphological, optical and electrical properties of pristine and irradiated ZnO thin films were characterized by X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR), scanning electron microscope (SEM), spectroscopy ellipsometry (SE) and four point probe technique respectively. XRD results showed that the crystallite size decreased from pristine value at the fluence 1?×?10¹³ ions/cm², with further increase of ion fluence the crystallite size also increased due to which the crystallinity of thin films improved. SEM micrographs showed acicular structures appeared on the ZnO thin film surface at high fluence of 5?×?10¹⁴ ions/cm². FTIR showed absorption band splitting due to the growth of ZnO nanostructures. The optical study revealed that the optical band gap of ZnO thin films changed from 3.08?eV (pristine) to 2.94?eV at the high fluence (5?× 10¹⁴ ions/cm²). The electrical resistivity of ZnO thin film decreases with increasing ion fluence. All the results can be attributed to localized heating effect by ions irradiation of thin films and well correlated with each other.     

Polyaminocarboxylate promoted synthesis of Hafnium/ Zirconium substituted anion excess In2O3: Structure,optical and electrical conductivity properties

The current study aimed to generate Hf/Zr substituted In₂O₃ with the ultimate aim of realizing a potential transparent conducting oxide. We applied a co-complexation method to bring the reactively dissimilar In and Hf/Zr together in one oxide network. We prepared an EDTA complex containing an equimolar concentration of In and Hf/Zr and examined their characteristics with FTIR and TG-DSC traces. Rietveld refinement results of calcined complexes and their Raman spectra confirmed the formation of anion excess bixbyite structure for (In_1-xM_x)₂O_3+δ (M = Hf, Zr, and x = 0.50). The lattice expanded after substituting with Hf/Zr, and the optical bandgap increased from 2.87 eV (In₂O₃) to 3.20–3.60 eV. The high percentage reflectance in the visible region and absorbance in the UV region fulfilled some of the prerequisites of transparent conducting oxide. Electrical resistivity reduced up to two orders in magnitude with increasing temperature for Hf and Zr incorporated In₂O₃.     

Synthesis,characterization, conductivity,band gap,and kinetic of thermal degradation of poly‐4‐[(2‐mercaptophenyl) imino methyl] phenol

The oxidative polycondensation reaction conditions of 4‐[(2‐mercaptophenyl) imino methyl] phenol (2‐MPIMP) were studied in an aqueous acidic medium between 40 and 90°C by using oxidants such as air, H₂O₂, and NaOCl. The structures of the synthesized monomer and polymer were confirmed by FTIR, ¹H NMR, ¹³C NMR, and elemental analysis. The characterization was made by TGA‐DTA, size exclusion chromatography (SEC) and solubility tests. At the optimum reaction conditions, the yield of poly‐4‐[(2‐mercaptophenyl) imino methyl]phenol (P‐2‐MPIMP) was found to be 92% for NaOCl oxidant, 84% for H₂O₂ oxidant 54% for air oxidant. According to the SEC analysis, the number‐average molecular weight (M_n), weight‐average molecular weight (M_w), and polydispersity index values of P‐2‐MPIMP were found to be 1700 g mol^?1, 1900 g mol^?1, and 1.118, using H₂O₂; 3100 g mol^?1, 3400 g mol^?1, and 1.097, using air; and 6750 g mol^?1, 6900 g mol^?1, and 1.022, using NaOCl, respectively. According to TG analysis, the weight losses of 2‐MPIMP and P‐2‐MPIMP were found to be 95.93% and 76.41% at 1000°C, respectively. P‐2‐MPIMP showed higher stability against thermal decomposition. Also, electrical conductivity of the P‐2‐MPIMP was measured, showing that the polymer is a typical semiconductor. The highest occupied molecular orbital, the lowest unoccupied molecular orbital, and the electrochemical energy gaps (E′_g) of 2‐MPIMP and P‐2‐MPIMP were found to be ?6.13, ?6.09; ?2.65, ?2.67; and 3.48, 3.42 eV, respectively. Kinetic and thermodynamic parameters of these compounds investigated by MacCallum‐Tanner and van Krevelen methods. The values of the apparent activation energies of thermal decomposition (E_a), the reaction order (n), pre‐exponential factor (A), the entropy change (ΔS*), enthalpy change (ΔH*), and free energy change (ΔG*) were calculated from the TGA curves of compounds. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effects of transition metal additives on redox stability and high-temperature electrical conductivity of (Fe,Mg)3O4 spinels

Magnetite-based spinels are considered as promising oxide materials to meet the requirements for ceramic consumable anodes in molten oxide pyroelectrolysis process, a breakthrough low-CO₂ steel technology aimed to overcome the environmental impact of classical extractive metallurgy. The present work focuses on the assessment of phase relationships, redox stability and electrical conductivity of Fe_2.6Me_0.2Mg_0.2O₄ (M = Ni, Cr, Al, Mn, Ti) spinel-type materials at 300–1773 K and p(O₂) from 10⁻⁵ to 0.21 atm. The oxidation state of substituting transition metal cation, affecting the fraction of Fe²⁺ in spinel lattice, was found to be a key factor, which determines the electronic transport and tolerance against oxidative decomposition, while the impact of preferred coordination of additives on these properties was less pronounced. At T > 650 K thermal expansion of Fe_2.6Me_0.2Mg_0.2O₄ ceramics exhibited complex behaviour, and, in highly oxidizing conditions, resulted in significant volume changes, unfavourable for high-temperature electrochemical applications.     

Role of Ni2+ substituent on the structural,optical and magnetic properties of chromium oxide (Cr2-xNixO3) nanoparticles

Pristine chromium oxide (Cr₂O₃) and nickel ions (Ni²⁺) substituted Cr₂O₃ nanoparticles were synthesized using a simple co-precipitation technique. The main objective of this work is to investigate Ni²⁺ substituent's role at different concentrations on the structural, morphological, optical, and magnetic properties of Cr₂O₃ nanoparticles. Structural analyses based on X-ray diffraction (XRD), Raman and Fourier transform infra-red (FTIR) data confirmed the successful incorporation of Ni²⁺ into Cr₂O₃ nanoparticles up to x = 0.05 of Ni²⁺ content, without affecting the rhombohedral crystal structure of Cr₂O₃ nanoparticles. Rietveld refinement results showed the variation in lattice parameters and cell volumes alongwith the substitution of Ni²⁺ into Cr₂O₃ nanoparticles. Raman and FTIR spectra also depicted a considerable shift in the characteristic vibration modes of Cr₂O₃ nanoparticles due to strain-induced by Ni²⁺ substitution. Beyond x = 0.05, the structural transformation took place from rhombohedral to cubic crystal structure. Subsequently, new peaks (apart from Cr₂O₃ phase modes) have been observed at x = 0.1 of Ni²⁺ content due to the formation of secondary phase i.e., nickel chromate (NiCr₂O₄). Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) illustrated the changes in the morphology of Cr₂O₃ nanoparticles with Ni²⁺ substitution. UV–Vis analysis revealed a narrowing of optical band energy (E_g) of Ni²⁺ substituted Cr₂O₃ nanoparticles from 3 to 1.85 eV as Ni²⁺ content varies from x = 0 to 0.2, respectively. Afterward, there is an increase in optical band gap energy (E_g) when Ni²⁺ content increased from x = 0.3 to 0.5, as NiCr₂O₄ started dominating the Cr₂O₃ phase. Single-phase Ni²⁺ substituted Cr₂O₃ nanoparticles exhibited a superparamagnetic behavior, whereas the multi-phase compound ascribed to both superparamagnetic and paramagnetic. These changes in optical and magnetic properties can lead to novel strategies to render applications in the field of optoelectronics and optomagnetic devices.     

Ferroelectric,upconversion emission and optical thermometric properties of color-controllable Er3+-doped Pb(Mg1/3Nb2/3)O3-PbTiO3-Pb(Yb1/2Nb1/2)O3 ferroelectrics

The (0.98-x)(0.6Pb(Mg_1/3Nb_1/3)O₃-0.4PbTiO₃)-xPb(Yb_1/3Nb_1/3)O₃-0.02Pb(Er_1/2Nb_1/2)O₃ ((0.98-x)(PMN-PT)-xPYN:Er³⁺) ceramics were prepared through a solid-state reaction method. The phase structure, piezoelectric response, ferroelectric performance and upconversion emission of the ceramics were systematically investigated. The phase structure, the electrical and optical properties are strongly related to the content of PYN. The optimized piezoelectric response and upconversion emissions of the ceramics were achieved near x = 0.12, which locates in the morphotropic phase boundary (MPB) composition. Furthermore, the temperature sensing behaviors of the resultant compounds based on the thermally coupled levels of ²H_11/2 and ⁴S_3/2 of Er³⁺ ions in the temperature range of 133–573 K were studied by utilizing the fluorescence intensity ratio technique. Additionally, the thermal effect, which is induced by the laser pump power, of the studied ceramics is also investigated and the produced temperature is enhanced from 268 to 348 K with the pump power rising from 109 to 607 mW.     

SPS-assisted synthesis of InGaO3(ZnO)m ceramics,and influence of m on the band gap and the thermal conductivity

In this study, we report on the use of a two-stage annealing treatment at 1100°C coupled to reactive Spark Plasma Sintering to reduce the synthesis temperature of InGaO₃(ZnO)_m (m = 1 to 9) dense polycrystalline pellets below 1200°C, in order to suppress the volatilization of ZnO and get a better control of the crystalline quality of the pellets. We show that using this treatment, dense single-phase pellets can be prepared with randomly oriented grains. Besides, we evidence a monotonic evolution of the band gap in the series from 3.27 eV in InGaO₃(ZnO) to 3.02 eV in InGaO₃(ZnO)₉, as well as a non-monotonic evolution of the lattice thermal conductivity that reaches a minimum for InGaO₃(ZnO)₃, lower than 2 W m⁻¹ K⁻¹ above 350°C. Last, we propose a procedure for the high-temperature measurement of the thermal diffusivity of oxides by the laser flash method to avoid possible reactions between the measured material and the graphite spray.     

Structural,optical and electrical properties of low temperature grown undoped and (Al,Ga) co-doped ZnO thin films by spray pyrolysis

Aluminum and gallium co-doped ZnO (AGZO) thin films were grown by simple, flexible and cost-effective spray pyrolysis method on glass substrates at a temperature of 230 °C. Effects of equal co-doping with aluminum (Al) and gallium (Ga) on structural, optical and electrical properties were investigated by X-ray diffraction (XRD), UV–vis–NIR spectrophotometry and Current–Voltage (I–V) measurements, respectively. XRD patterns showed a successful growth with high quality polycrystalline films on glass substrates. The predominant orientation of the films is (002) at dopant concentrations ≤2 at% and (101) at higher dopant concentrations. Incorporation of Al and Ga to the ZnO crystal structure decreased the crystallite size and increased residual stress of the thin films. All films were highly transparent in the visible region with average transmittance of 80%. Increasing doping concentrations increased the optical band gap, from 3.12 to 3.30 eV. A blue shift of the optical band gap was observed from 400 nm to 380 nm with increase in equal co-doping. Co-doping improved the electrical conductivity of ZnO thin films. It has been found from the electrical measurements that films with dopant concentration of 2 at% have lowest resistivity of 1.621×10⁻⁴ Ω cm.     

The effects of in-situ formed phases on the microstructure,mechanical properties and electrical conductivity of spark plasma sintered B4C containing Y2O3

B₄Cs without additive and 5, 10 and 15 wt % Y₂O₃ containing B₄Cs were produced by using spark plasma sintering (SPS) technique at different temperatures such as 1820, 1930 and 2030 °C and the effects of in-situ formed phases on the mechanical properties and electrical conductivity of B₄C were investigated. Microstructural investigations showed that the YB₄ phase was formed at 1820 °C and the YB₆ phase at 1930 °C. The hardness values of B₄C-YB₄ composites were higher than the value of B₄C sintered at 1820 °C while lower than that of sintered at 2030 °C. The fracture toughness steadily increased with increasing Y₂O₃ content. The electrical conductivity of B₄C sintered at 2030 °C increased by ～ 40 % with the contribution of in-situ formed YB₄ phase. Compared to B₄C-YB₄, B₄C-YB₆’s hardness was higher, while its fracture toughness and electrical conductivity were lower.     

Enhancing the electrical conductivity of vanadate glass system (Fe2O3, B2O3, V2O5) via doping with sodium or strontium cations

Novel glass-ceramics of the nominal molar compositions 20Fe₂O₃·20B₂O₃·(60-x)V₂O₅· (xNa₂O or xSrO) (where x?=?0 or 10) were prepared by traditional melt technique. Differential thermal analysis (DTA) was implemented to study the thermal behavior of the prepared glasses. Vanadium pentoxide (V₂O₅), iron vanadate (FeVO₄), sodium vanadate (Na₃VO₄) and strontium vanadate (with different formulae) were crystallized and identified by X-ray diffraction (XRD) analysis under certain conditions of heat-treatment. Further characterization of glass and glass ceramics samples were performed using scanning electron microscope (SEM), density, electrical and dielectric measurements. In conclusion, our study elucidated that the substitution of vanadium by Na⁺ and Sr²⁺ ions enhanced the conductivity at 180?°C from 5.11?×?10^?4 for unmodified glass to 2.93?×?10^?3 and 1.03?×?10^?2?S?cm^?1 for Na- and Sr-modified glasses.     

Synthesis,characterization, thermal stability,conductivity, and band gap of a new aromatic polyether containing an azomethine as a side

In this study, the oxidative polycondensation reaction conditions of 4‐[(4‐methylphenyl)iminomethyl]phenol (4‐MPIMP) were studied by using oxidants such as air O₂, H₂O₂, and NaOCl in an aqueous alkaline medium between 50 and 90°C. The structures of the synthesized monomer and polymer were confirmed by FTIR, UV–vis, ¹H–¹³C‐NMR, and elemental analysis. The characterization was made by TGA‐DTA, size exclusion chromatography (SEC), and solubility tests. At the optimum reaction conditions, the yield of poly‐4‐[(4‐methylphenyl)iminomethyl]phenol (P‐4‐MPIMP) was found to be 28% for air O₂ oxidant, 42% for H₂O₂ oxidant, and 62% for NaOCl oxidant. According to the SEC analysis, the number–average molecular weight (M_n), weight–average molecular weight (M_w), and polydispersity index values of P‐4‐MPIMP were found to be 4400 g mol^?1, 5100 g mol^?1, and 1.159, using H₂O₂, and 4650 g mol^?1, 5200 g mol^?1, and 1.118, using air O₂, and 5100 g mol^?1, 5900 g mol^?1, and 1.157, using NaOCl, respectively. According to TG analysis, the weight losses of 4‐MPIMP and P‐4‐MPIMP were found to be 85.37% and 72.19% at 1000°C, respectively. P‐4‐MPIMP showed higher stability against thermal decomposition. Also, electrical conductivity of the P‐4‐MPIMP was measured, showing that the polymer is a typical semiconductor. The highest occupied molecular orbital and the lowest unoccupied molecular orbital energy levels and electrochemical energy gaps (E) of 4‐MPIMP and P‐4‐MPIMP were found to be ?5.76, ?5.19; ?3.00, ?3.24; 2.76 and 1.95 eV, respectively. According to UV–vis measurements, optical band gaps (E_g) of 4‐MPIMP and P‐4‐MPIMP were found to be 3.34 and 2.82 eV, respectively. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007