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Bi0.9Nd0. 1Fe1–xCoxO3 (x = 0.025, 0.050, 0.075 and 0.1) solid solutions have been synthesized by doping of Co3+ at the Fe3+ site using solid-state reaction method. The prepared solid solutions have...

In the present study, optical and electrical properties of e-beam-deposited Ni/indium–tin oxide (5/50 nm) contacts are studied and compared with semi-transparent Ni/Au (5/5 nm) contacts. The normalized transmittance of 560 °C annealed Ni/ITO and Ni/Au films was recorded 86% and 73.1% at 463 nm, respectively. The current–voltage characteristics of both annealed contacts exhibit the linear behavior. The specific contact resistances for Ni/Au and Ni/ITO contacts were recorded 1.29 × 10−3 Ω cm2 and 1.76 × 10−1 Ω cm2, respectively. The forward voltages (VF) of LEDs for both contacts (Ni/Au and Ni/ITO p-contacts) at 20 mA current injection were found 2.8 V and 3.11 V, respectively. It is clear that electrical properties of LEDs with Ni/Au contacts are found much better compared to LEDs with Ni/ITO p-contacts. On the other hand, optical characteristics of LEDs with Ni/ITO contacts showed better optical properties compared to LEDs with Ni/Au contacts. The better optical properties were attributed to more transparent nature of ITO film in the visible range. With a 20 mA current injection, the electroluminescence (EL) intensity of blue LED with Ni/ITO p-contact was 14.9% higher than LED with Ni/Au contacts.

Strontium and Niobium doped CCTO with the chemical composition Ca0.95Sr0.05Cu3Ti3.98Nb0.02O12 was processed by conventional solid state reaction method. X-Ray diffraction pattern confirmed the single phase formation of the synthesized sample. Dielectric measurement performed to study the frequency and temperature effect on the dielectric constant as well as dielectric losses of the prepared sample. Temperature and frequency dependent conductivity studies were carried out in the temperature range 293K to 573K and frequency in the range of 1Hz to 10MHz.

The glass system with composition 55B2O3.10K2O.(35-x)CaO.xMgO (x=0,5,10,15) has been prepared using normal melt quench process. XRD measurement was done to verify the non-crystalline nature of the glass system. The glass transition temperature was calculated using DSC and was found to increase initially at low content of MgO and decreased at high content of MgO. Various physical properties density, molar volume are also calculated. The optical band gap is measured using UV-VIS spectroscopy.

Lithium zinc boro tellurite glasses with compositions xLi2O-(100-x) [0.25ZnO–0.15B2O3–0.60TeO2] [where x = 0, 5, 10, 15 and 20 mol%] have been prepared by melt-quench technique. The amorphous nature of the prepared system is ascertained by X-ray diffraction. The density and molar volume are found to decrease with the increase in concentration of Li2O. The differential scanning calorimetry is used to calculate the glass transition temperature (Tg) and the observed values are found to be decreased. The IR and Raman spectra indicate that Li2O acts as a network modifier in the glass matrix. In the present system, tellurium exists as TeO4 and TeO3, B2O3 in the form of BO4 and BO3 and zinc oxide exists as ZnO4 structural units. The values of the optical band gap are estimated from the fitting of Mott and Davis’s and model. A better convergence is achieved between experimental observed spectra of absorption coefficient and hydrogenic excitonic model. The optical band gap energy increases, whereas refractive index and molar refractivity follow the reverse trend with Li2O. The range of metallization criterion suggests that these glasses may be a potential candidate for nonlinear optical materials.

A quaternary glass system with compositions TeO2-Bi2O3-B2O3-BaO has been prepared by melt-quench method. The calculated values of density, molar volume and crystalline volume were found to increase with bismuth content. The absorption edge shifts towards lower wavelength side for all the compositions except x = 20 mol%. The optical band gap energy has been evaluated from extrapolation of Tauc’s plot results and Urbach energy has been estimated from linear fitting. The other optical parameters such as refractive index, molar refractivity and metallization criterion have also been discussed.

Lead free polycrystalline ceramics with compositional formula Ba 0.90 Ca 0.10 Ti 1–3 x /4 Fe x O 3 (BCT), ( x =0.000, 0.005, 0.010, 0.015 and 0.020) were prepared by the solid state reaction method. The effect of substitution of Fe 3+ ion at Ti-site on the ferroelectric and piezoelectric properties of BCT ceramics was studied. Remanant polarisation ( P r ) and saturation polarisation ( P s ) show an increasing trend while the reverse trend was observed for coercive field ( E c ) with Fe 3+ substitution. The values of the piezoelectric charge coefficient ( d 33 ) and piezoelectric coupling coefficient ( k p ) was found to increase with increase in Fe content. Ceramic sample with x =0.02 was found to have a maximum value of d 33 (130 pC/N) and k p (29%). The prepared ceramic samples show magnetic properties as confirmed by recorded MH loops. On substitution of Fe 3+ ions, the ferroelectric BCT ceramics show clear transformation of the diamagnetic nature of BCT ceramics to weak ferromagnetism.

Glasses having composition 60TeO2-15V2O5-(25-x) ZnO-xLi2O where x= 0, 5, 10 mol% were prepared by standard melt quench technique. The glass transition temperature is measured by DSC technique using TA instrument and found to decrease with increase in Li2O signifies that glass formation tendency, thermal stability and compactness of glass structure decreases. The deconvolution of FTIR spectra evidenced the existence of TeO4, TeO3 and TeO6 structural units in glass network and vanadium exists as VO4 and VO5 structural units.

The ac conductivity of tellurium based quaternary glasses having composition 60 TeO 2 – 10 ZnO – (30 − x) B 2 O 3 – xBi 2 O 3 ; x = 0, 5, 10, 15 and 20 has been investigated in the frequency range 10 −1 Hz to 10 5 Hz and in the temperature range 483 K–593 K. The frequency and temperature dependent ac conductivity increase with increase in bismuth content and found to obey Jonscher's universal power law. The dc conductivity, crossover frequency and frequency exponent have been estimated from the fitting of the experimental data of conductivity with Jonscher's universal power law. In the studied glasses the ac conduction may be described by overlapping of large polaron tunneling model. The activation energy is found to be decrease with increase in bismuth content and variable range hopping (VRH) proposed by Mott with some modification suggested by Punia et al. is more or less suitable to explain dc conduction. The value of the stretched exponent (β) obtained by fitting of M″ reveals the presence of non-Debye type of relaxation in the presently studied glass samples. Scaling spectra of electric modulus (M′ and M″) collapse into a single master curve for all the compositions and temperatures. The values of activation energy of electric modulus (E R ) and conduction (W) are nearly equal for all the studied glasses, indicating that the polaron have to overcome the same energy barrier during conduction as well as relaxation processes. The conduction and relaxation process in the presently studied glass samples are composition and temperature independent.

Quaternary bismuthate glasses with compositions xB2O3–(80 − x) Bi2O3–15SiO2–5TeO2 have been prepared by melt-quench technique. X-ray diffraction studies were performed to ascertain the amorphous nature of samples. The density, molar volume and crystalline volume decrease with increase in B2O3 content whereas the glass transition temperature shows the reverse trend. The Raman and FTIR spectra of the studied glasses indicate that B2O3 has been found to exist in the form of BO3 trigonal and BO4 tetrahedral structural units and vibrations corresponding to these structural units increase with increase in B2O3 content. SiO2 is present in the form of SiO4 tetrahedral structural units and TeO2 in the form of TeO3 structural units. Bismuth plays the role of network modifier [BiO6 octahedra] as well as network former [BiO3 pyramids] for all the glass compositions. The optical band gap energy has been calculated from the fitting of both Mott and Davis’s model and Hydrogenic excitonic model with the experimentally observed absorption spectra. A good fitting of experimental data with HEM indicates the excitonic formation in the studies glass system. The values of optical band gap energy show nonlinear behavior due to the structural changes that take place in the present glass samples. The Urbach energy calculated using Urbach empirical formula for studied glass samples suggest the possibility of reduction in defect concentrations. The metallization criterion of the presently studied samples suggests that the prepared glasses may be potential candidates for nonlinear optical applications.

The ac conductivity and electric modulus formalism of bismuth silicate glasses containing manganese with compositions xMnO2·(60 − x)Bi2O3·40SiO2, (x = 0, 5, 10, 15 and 20) have been studied in the frequency range 10− 1 Hz to 1 MHz and temperature range 583 K to 703 K. The ac conductivity is found to increase with an increase in MnO2 content. The frequency dependent conductivity for manganese doped bismuth silicate glassy system shows a single plateau for samples with x = 0 and 5, but for glasses with x = 10, 15 and 20, the temperature and frequency dependent conductivity shows a double plateau in the whole temperature range 583 K to 703 K. The observed dispersive behavior of ac conductivity of bismuth silicate glasses containing manganese is discussed in the framework of Jonscher's universal power law fitted to the experimental data of samples showing single as well as two plateau regions. The results show that the ac conductivity increases with the increase in the frequency of applied field. Further, it is observed that small polaron conduction mechanism is more or less suitable to explain the conduction in the present glass samples with x = 10, 15 and 20 in the high frequency region. However, the temperature dependent behavior of the frequency exponent s for glass samples with x = 0 and 5 seems to follow CBH conduction mechanism. The electrical relaxation is rationalized using the electric modulus formulation in the presently studied glasses at all the temperatures. The values of activation energy for dc conduction (EA) and electric modulus (ER) were estimated. For glass sample with x = 0 and 5, the activation energy associated with electric modulus is almost equal to that of the dc conductivity at the low frequency range, whereas for glass samples with x = 10, 15 and 20, the values of ER are equal to the activation energy due to dc conduction in the high frequency region.

Glass system with compositions xMnO2–(60−x) Bi2O3–40SiO2 have been synthesized by standard melt quench technique. X-ray diffraction patterns confirm the amorphous nature of as-prepared glass samples. The values of density have been measured and molar volume determined is found to decrease with increase in MnO2 content. Theoretical calculations of crystalline volume (Vc) have also been made. The glass transition temperature (Tg) determined using differential scanning calorimetry (DSC) is observed to increase with increase in MnO2 content. The structural analysis has been carried out using FTIR and Raman spectroscopy. In the present glass system, MnO2 acts as network modifier and exists in MnO6 structural units. Bismuth acts both as network former with BiO3 pyramidal units as well as network modifier with BiO6 octahedral units in the present glass system. SiO2 exists in form of SiO4 tetrahedral structural units with two non-bridging oxygens (NBO’s). The optical band gap energy (Eg) has been estimated from Tauc’s plot for direct transitions, it decreases with increase in manganese content.

Bismuth silicate glasses mixed with different concentrations of titanium dioxide having compositions xTiO2–(60−x)Bi2O3–40SiO2 with x=0, 5, 10, 15 and 20 were prepared by the normal melt quench technique. The frequency dependence of the ac electrical conductivity of different compositions of titanium bismuth silicate glasses has been studied in the frequency range 10−1 Hz to 10 MHz and in the temperature range 623–703 K. The temperature and frequency dependent conductivity is found to obey Jonscher׳s universal power law for all the compositions of titanium bismuth silicate glass system. The dc conductivity (σdc), so called crossover frequency (ωH), and frequency exponent (s) have been estimated from the fitting of experimental data of ac conductivity with Jonscher׳s universal power law. Enthalpy to dissociate the cation from its original site next to a charge compensating center (Hf) and enthalpy of migration (Hm) have also been estimated. The conductivity data have been analyzed in terms of different theoretical models to determine the possible conduction mechanism. Analysis of the conductivity data and the frequency exponent shows that the correlated barrier hopping of electrons between Ti3+ and Ti4+ ions in the glasses is the most favorable mechanism for ac conduction. The temperature dependent dc conductivity has been analyzed in the framework of theoretical variable range hopping model (VRH) proposed by Mott which describe the hopping conduction in disordered semiconducting systems. The various polaron hopping parameters have also been deduced. Mott׳s VRH model is found to be in good agreement with experimental data and the values of inverse localization length of s-like wave function (α) obtained by this model with modifications suggested by Punia et al. are close to the ones reported for a number of oxide glasses.

Iron bismuth silicate glasses have been successfully synthesized by melt quenching technique. The amorphous nature of the glass samples is ascertained by the XRD patterns. The values of density, molar volume and crystalline volume have been measured and are found to decrease with increase in iron content. The glass transition temperature measured using Differential Scanning Calorimetry (DSC) also varies with increase in Fe2O3 content. The Raman and FTIR spectra of the studied glass system taken at room temperature suggests that Fe2O3 modifies the structure of bismuth silicate glasses and it acts as both network modifier as well as network former. Bismuth also plays the role of both network modifier (BiO6 octahedra) as well as network former (BiO3 pyramids) and SiO2 exists in SiO4 tetrahedral structural units with two non-bridging oxygens. The Hydrogenic excitonic model is found to be applicable to the studied glass compositions. The variation in Urbach energy value observed for the studied glass samples suggests the possibility of increase in the number of glass defects. The metallization criterion for the synthesized glass samples is determined and found to be in the range 0.30–0.38.

Glass system with compositions x TiO 2 ·(60 − x )Bi 2 O 3 ·40SiO 2 has been prepared by standard melt quench technique. The amorphous nature of the glass samples has been ascertained by the X-ray diffraction. It is observed that density and molar volume of the studied glasses decrease with increase in TiO 2 content whereas the glass transition temperature shows the reverse trend; indicating the increase in compactness of the glass structure with increase in TiO 2 content. The Raman and FTIR studies reveal that on addition of TiO 2 , some of SiO 4 tetrahedra units with three non-bridging oxygens (NBOs) per silicon are converted into SiO 4 tetrahedral units with four NBO per silicon and number of network forming BiO 3 pyramidal units goes on decreasing and no BiO 3 pyramidal units are observed in glass composition with x = 20. Bismuth plays the role of network modifier with BiO 6 octahedral units for all the studied glass compositions. TiO 2 acts as network former with TiO 4 tetrahedral units in all the glass compositions having titanium besides acting as network modifier TiO 6 octahedral units in glass compositions with x = 10, 15 and 20. However, the glass composition with x = 15 has maximum number of TiO 4 structural units among all the studied glass compositions.

Tellurium oxide based quaternary glasses in the system TeO2⋅B2O3⋅Bi2O3⋅ZnO have been prepared by melt quenching technique. Amorphous nature of the samples has been ascertained by X-ray Diffractogram. The values of density and molar volume increase with increase in Bi2O3 content. Theoretical calculations of crystalline volume (Vc) have also been made. The glass transition temperature (Tg) has been determined using differential scanning calorimetry (DSC) and its value is observed to decrease with increase in Bi2O3 content. IR and Raman spectra of the present glass system indicate that ZnO acts as network modifier and exists in ZnO4 units. TeO2 exists as TeO3, TeO4, and TeO6 structural units and the number of TeO4 groups decreases with increase in bismuth content except for the glass sample with x = 5, which shows maximum number of TeO4 structural units among all other studied glass samples and transformation of some of TeO4 structural units into TeO3 structural units is observed with increase in bismuth content. Bismuth plays the role of network modifier with BiO6 octahedral structural units for glass samples with x = 5, 10, and 15, whereas, exists in network forming BiO3 pyramidal structural units for glass sample with x = 20. B2O3 exists in the form of BO3 trigonal and BO4 tetrahedral structural units. The transmittance of the present glasses is observed to be very high (up to 95%) in the spectral range (λ = 2.5–6.5 μm) which is of great technological importance. The percentage value of transmittance increases with increase in Bi concentration. The Hydrogenic excitonic model is applicable to the presently studied glasses and the optical band gap energies (Eg) calculated from this model and Tauc’s plots for direct transitions are almost same. Eg decreases with increase in bismuth content, however, the molar refractivity (Rm) show the reverse trend. Metallization criterion for these materials shows that these glasses may be potential candidates for non linear applications.

Iron-containing bismuth silicate glasses with compositions 60SiO2·(100−x)Bi2O3·xFe2O3 have been prepared by conventional melt-quenching technique. The amorphous nature of the glass samples has been ascertained by the X-ray diffraction. The density (d) has been measured using Archimedes principle, molar volume (Vm) has also been estimated, and both are observed to decrease with the increase in iron content. The glass transition temperature (Tg) of these iron bismuth silicate glasses has been determined using differential scanning calorimetry (DSC) technique, and it increases with the increase in Fe2O3 content. The IR spectra of these glasses consist mainly of [BiO6], [BiO3], and [SiO4] structural units. The optical properties are measured using UV-VIS spectroscopy. The optical bandgap energy (Eop) is observed to decrease with the increase in Fe2O3 content, whereas reverse trend is observed for refractive index.

Zinc bismuth silicate glasses with compositions 40SiO2·xZnO·(60-x)Bi2O3 (x=0,5,10,15,20,25,30,35, and 40) have been prepared by conventional melt-quench technique and the solubility limit of zinc in bismuth silicate glass system has been estimated using X-ray diffraction technique. Density has been measured using Archimedes' principle; with increase in ZnO in the samples, the molar volume and density are found to decrease. The glass transition temperature (Tg) has been determined by using differential scanning calorimetry (DSC) and is observed to increase with increase in ZnO content. Raman and FTIR spectra have been recorded at room temperature and the analysis of Raman and FTIR shows that in all the glass compositions, asymmetric and symmetric stretched vibrations of Si–O bonds in SiO4 tetrahedral units exist and with decrease in Bi2O3, the contribution of symmetric vibrations begins to dominate which results in increased compactness of the glass structure.

The optical characterization of glass samples in the system 40SiO2·xZnO · (60-x)Bi2O3withx=0, 5, 10, 15, 20, 25, 30, 35, and 40 prepared by conventional melt-quench technique has been carried out in the light of Hydrogenic Excitonic Model (HEM). The absorption coefficient spectra show good agreement with theoretical HEM for the present glass system and the values of different parameters likeEg,R,Γ1,Γc, andCohave been estimated from fitting of this model. The values of energy band gap estimated from fitting of HEM with experimental data are in good agreement with those obtained from Tauc’s plot for direct transitions. The band gap energy is found to increase with increase of ZnO content. The decrease in values of Urbach energy with increase in ZnO content indicates a decrease in defect concentration in the glass matrix on addition of ZnO content. Optical constantsnandkobeyk-kconsistency and the dielectric response of the studied glass system is similar to that obtained for Classical Electron Theory of Dielectric Materials. The calculated values of the metallization criterion (M) show that the synthesized glasses may be good candidates for new nonlinear optical materials.

Iron containing bismuth silicate glasses with compositions 70SiO2⋅(100-x)Bi2O3⋅xFe2O3 have been prepared using conventional melt-quenching method and their amorphous nature has been investigated using XRD. Density has been measured using Archimedes’ principle and molar volume (Vm) have also been estimated. With increase in Fe2O3 content, there is a decrease in density and molar volume of the glass samples. The glass transition temperature (Tg) have been determined using Differential Scanning Calorimetry (DSC) and are observed to increase with increase in Fe2O3 content. In the present glass system bismuth and iron plays the role of network modifier and the symmetry of silicate network goes on increasing with Fe2O3 content and it modifies the physical and structural properties of these glasses.

The dc conductivity measured in a wide range of temperatures (room temperature to 533.16 K) for glass samples of compositions 50V2O5·xBi2O3·(50-x) ZnO; x = 0, 5, 10, 15, and 20, is discussed in this paper. The temperature dependent dc conductivity has been analyzed in the framework of various theoretical models, which describe the hopping conduction in disordered semiconducting systems. It has been observed that Mott's model of polaron hopping in transition metals is in good agreement with the experimental data in high as well as intermediate temperature regions. The various polaron hopping parameters have also been deduced. It has been ascertained by these estimated quantities and different approaches that the electrical conduction in present glass system is due to non-adiabatic variable range hopping of small polarons. Moreover, it has been found that Mott's and Greaves’ variable range hopping models are in good agreement with the experimental data in the whole studied temperature range in the present i...

The ac conductivity of bismuth zinc vanadate glasses with compositions 50V2O5. xBi2O3. (50-x) ZnO has been studied in the frequency range 10−1 Hz to 2 MHz and in temperature range 333.16 K to 533.16 K. The temperature and frequency dependent conductivity is found to obey Jonscher's universal power law for all the compositions of bismuth zinc vanadate glass system. The dc conductivity (σdc), crossover frequency (ωH), and frequency exponent (s) have been estimated from the fitting of experimental data of ac conductivity with Jonscher's universal power law. Enthalpy to dissociate the cation from its original site next to a charge compensating center (Hf) and enthalpy of migration (Hm) have also been estimated. It has been observed that mobility of charge carriers and ac conductivity in case of zinc vanadate glass system increases with increase in Bi2O3 content. In order to determine the conduction mechanism, the ac conductivity and its frequency exponent have been analyzed in the frame work of various theore...

Zinc bismuth vanadate glasses with compositions 50V2O5-xBi2O3-(50-x) ZnO have been prepared using a conventional melt-quenching method and the solubility limit of Bi2O3 in zinc vanadate glass system has been investigated using x-ray diffraction. Density has been measured using Archimedes’ principle; molar volume (Vm) and crystalline volumes (Vc) have also been estimated. With an increase in Bi2O3 content, there is an increase in density and molar volume of the glass samples. The glass transition temperature (Tg) and Hurby coefficient (Kgl) have been determined using differential scanning calorimetry (DSC) and are observed to increase with increase in Bi2O3 content (i.e., x), up to x = 15, thereby indicating the structural modifications and increased thermal stability of zinc vanadate glasses on addition of Bi2O3. FTIR spectra have been recorded and the analysis of FTIR shows that the structure depends upon the Bi2O3 content in the glass compositions. On addition of Bi2O3 into the zinc vanadate system, the structure of V2O5 changes from VO4 tetrahedral to VO5 trigonal bi-pyramid configuration. The optical parameters have been calculated by using spectroscopic ellipsometry for bulk oxide glasses (perhaps used first time for bulk glasses) and optical bandgap energy is found to increase with increase in Bi2O3 content.