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This study, reports the exhalation rates of radon and thoron from surface soil collected from 60 rural sites of district Hisar, Haryana, India. The exhalation rates of Rn222 (Radon)& Rn220(Thoron) were measured by portable SMART RnDuo (AQTEK SYSTEMS) using a mass accumulation chamber which is equipped with a scintillation material coated cell. Dose rate due to Natural gamma radiations ranged 0.526 to 1.139 mSv y− 1. The Rn222mass exhalation rate in soil samples varied from 0.14 to 94.65 mBq kg− 1 h− 1. Thoron surface exhalation rates ranged 46.42 to 619.88 mBq m− 2 h− 1. This study give an idea about the differences in Rn222 & Rn220 exhalation at different locations which may be due to variations in geological structure of the locations and characteristics of the top soil.The findings show that using soil of the study area as building material is safe.

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...

Solid solutions of Bi0.9Nd0.1Fe1−xTixO3 have been prepared using conventional solid state reaction route. The Rietveld refinements of XRD patterns of all samples confirm the rhombohedral st...

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.

In the present study, optical and electrical properties of e-beam deposited Ni/Au/ITO (1.5/1/50 nm) contacts on p-GaN are investigated and compared with conventional thin Ni/Au (5/5 nm) semitransparent p-contacts. The contacts were annealed at 560 °C for 5 min in N2 + O2 ambient in a rapid thermal annealing system. The current–voltage (I–V) characteristics of both metal schemes showed linear behavior. The specific contact resistances and sheet resistances extracted from measured resistance versus contact pads spacing of Ni/Au and Ni/Au/ITO contacts were recorded ~ 2.71 × 10−3 Ω-cm2, 4.94 × 10−4 Ω-cm2, 2.021 × 105 Ω/□ and 2.1898 × 105 Ω/□, respectively. The normalized transmittance of Ni/Au/ITO film was recorded 81.6% at 463 nm, which was 8.5% higher than the conventional Ni/Au film (73.1%). Scanning electron microscopy images of contacts showed that the adhesion quality of Ni/Au/ITO contacts was superior to annealed Ni/Au contacts. It was found that electroluminescence intensity was higher (7.5%) for LED chip with Ni/Au/ITO p-contacts than LED chip with Ni/Au contacts. The forward voltages (VF) of LEDs with Ni/Au and Ni/Au/ITO contacts at 20 mA current injection were found 2.8 V and 2.91 V, respectively. These results indicate that Ni/Au/ITO may be used as transparent p-contacts for fabrication of high-performance GaN LEDs due to their better optical and adhesive properties compared to the conventional Ni/Au (5/5 nm) contacts on p-GaN.

Lead free polycrystalline ceramic sample of Cr doped BZT with composition BaZr0.045(CrxTi1-3x/4)0.955O3 (x=0.02) was synthesized by solid-state reaction method. The investigated study gives a basic idea about structural and dielectric properties of Cr-doped BZT ceramics. Using XRD technique the formation of the single phase crystalline structure was confirmed. The dielectric properties were measured using impedence analyzer in the wide frequency (10Hz to 10MHz) and temperature range (room temperature to 400°C). The static value of dielectric constant at high frequencies was observed which evidences the relaxor type behavior of ferroelectric. The considerable shifting of Curie temperature towards higher temperature (from 387K to 397K) supports ferroelectricity in Cr doped BZT ceramics which makes it a suitable candidate for energy storage and sensor applications.

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.

Lead free Mn doped barium zirconium titanate ceramic of composition BaZr0.045 (MnxTi1-x)0.955O3 (x = 0.00, 0.01, 0.02) were prepared by solid state reaction method. Tetragonal perovskite structure was confirmed by Rietveld refinement of X-ray diffraction pattern. Analysis of Scanning electron microscope (SEM) micrographs revealed that addition of Mn up to a certain limit accelerates grain growth of BZT ceramic. Static dielectric constant was successfully extended up to high frequencies with an appreciable decrease in dielectric loss about 70% for Mn doped BZT ceramics. The experimental data fitted with Curie Weiss Law and Power Law confirmed first order transition and diffusive behavior of the investigated system. The shifting of Curie temperature (Tc) from 387 K to 402 K indicated tendency for sustained ferroelectricity in doped BZMT ceramics. High value of percentage temperature coefficient of capacitance TCC >10% near Tc was observed for all the compositions and increases with Mn content in pure BZT. At room temperature, BZT modified ceramic corresponding to x = 0.01 composition shows better values of remnant polarization (Pr = 5.718 μC/cm2), saturation polarization (Ps = 14.410 μC/cm2), low coercive field (Ec = 0.612 kV/cm), and highest value of Pr/Ps = 0.396.

Mn doped barium zirconate titanate lead free ceramic with formula BaZr.045(MnxTi1-x) .955 O3 for x = 0.00, 0.01, 0.02 and 0.03 has been prepared by solid-state reaction method. The single phase tetragonal structure was confirmed by X-ray diffraction (XRD) pattern using Rietveld refinement. Scanning electron microscopy (SEM) shows an inhomogeneous distribution of randomly oriented grains with some voids. Electrical conductivity of Mn doped BZT ceramics was studied using impedance analyzer in the temperature range 493K–673K over wide frequency window. The dispersion behaviour in electrical conductivity obeys Jonscher's double power law for Mn free compound, while it follows single power law for Mn doped compositions. Various parameters viz. dc conductivity (σdc), pre-exponential factor (A), frequency exponent (s) and activation energy (Ea) have been estimated by the theoretical fitting of experimental data. The reciprocal temperature dependence of dc conductivity follows the Arrhenius law and specifies thermally activated conduction mechanism. The obtained value of activation energy (Ea) evidences the conduction mechanism is induced by the migration of oxygen vacancies and oxide ions. All samples shows Negative temperature coefficient of resistance (NTCR) and hence exhibit semiconducting behaviour. The environmental friendly lead free ceramic can be exploit to design advanced materials and suitable for the fuel cell electrolyte/electrode applications.

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.

The unique dielectric properties of CaCu3Ti4O12 (CCTO) are a promising feature for capacitor applications. Polycrystalline Ca0.95Nd0.05Cu3Ti3.95Zr0.05O12 ceramic was synthesized via conventional so...

The ac conductivity of halide based tellurium glasses having composition 70 TeO2-(30-x) BaO-x ZnCl2; x = 5, 10, 15, 20 and 25 has been investigated in the frequency range 10-1 Hz to 105Hz and in the temperature range 453 K to 553 K. The frequency and temperature dependent ac conductivity show mixed behaviour with increase in halide content and found to obey Jonscher’s universal power law. The values of dc conductivity, crossover frequency and frequency exponent have been estimated from the fitting of experimental data of ac conductivity with Jonscher’s universal power law. For determining the conduction mechanism in studied glass system, frequency exponent has been analyzed by various theoretical models. In presently studied glasses, the ac conduction takes place via overlapping large polaron tunneling (OLPT). The values of activation energy for dc conduction (W) and the one associated with relaxation process (E R) are found to increase with increase in x up to glass sample with x = 15 and thereafter it decrease with increase in zinc chloride content. DC conduction takes place via variable range hopping (VRH) as proposed by Mott with some modification suggested by Punia et al. The value of real part of modulus (M') is observed to decrease with increase in temperature. The value of stretched exponent (β) obtained from fitting of M'' reveals the presence of non-Debye type of relaxation in presently studied glass samples. Scaling spectra of ac conductivity and values of electric modulus (M' and M'') collapse into a single master curve for all the compositions and temperatures. The values of relaxation energy (E R) for all the studied glass compositions are almost equal to W, suggesting that polarons have to overcome same barrier while relaxing and conducting. The conduction and relaxation processes in the studied glass samples are composition and temperature independent.

The quaternary glass system xSiO 2 -(80-x) Bi 2 O 3 15B 2 O 3 5TeO 2 has been prepared by melt-quench technique. The amorphous nature of glass samples has been ascertained by X-ray diffraction patterns. The variations in density, molar volume and crystalline volume with glass compositions have been discussed. A non-linear change has been observed in glass transition temperature and optical band gap energy. Raman and FTIR spectral studies suggest that glass network is mainly built up of BO 3 , BO 4 , SiO 4 , and TeO 3 structural units, whereas BiO 3 exists as both network modifying [BiO 6 ] octahedral as well as network forming [BiO 3 ] pyramidal structural units. The values of optical band gap energy have been estimated from fitting of both Mott and Davis's model and Hydrogenic excitonic model (HEM) with experimental data of absorption spectra. The HEM model shows good agreement with experimentally observed absorption spectra, which indicates the exciton formation in studied glass system. The non-linear compositional change in optical band gap energy is related with the structural changes occurring in present glass samples. The Urbach energy has also been estimated. The range of metallization criterion suggests that prepared glasses may be considered as new 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.

A metallization scheme of Pt/Ag/Ni/Au (0.6/120/20/40 nm) metal layers with high reflectance and good surface morphology has been developed for obtaining low resistance ohmic contact on p-GaN. These metal layers were deposited by electron beam evaporation system on p-GaN. The metal contacts were annealed in different ambient conditions (N2, air and N2 + O2). The as-deposited contacts exhibit nonlinear current-voltage behaviour with reflectivity of ~95% at 470 nm wavelength. The air annealed Pt/Ag/Ni/Au contacts at 500 °C exhibit linear current-voltage behaviour with low specific contact resistance of 2.4 × 10−2 Ω-cm2. The reflectivity of air annealed contact at 500 °C was decreased to ~88.4% at ~470 nm compared to as-deposited contacts (~95%).

InGaN/GaN multiple quantum wells (MQWs) light-emitting diodes (LEDs) with Ni/ITO (5/50 nm) and Pt/ITO (0.8/50 nm) current spreading layer were investigated. The electrical and optical properties of Ni/ITO and Pt/ITO films were also investigated. It was found that the normalized transmittance of Ni/ITO and Pt/ITO films could reach 79.22 and 78.98% at 460 nm, which was almost equal. It was also found that Pt/ITO had showed better linear current–voltage characteristics compared to Ni/ITO contacts. The specific contact resistance for Pt/ITO contacts was 5.88 × 10−2 Ω cm2, while for Ni/ITO contacts, it was 5.66 × 10−1 Ω cm2 i.e. ~10 time more. The EL intensity of blue LED was much higher with Pt/ITO p-contact compared to Ni/ITO p-contact. The forward voltages (VF) of LEDs for two contacts (Ni/ITO and Pt/ITO p-contacts) at 20 mA current injection were found 4.49 and 3.5 V, respectively.

Lead-free V doped Barium Zirconium Titanate (BZT) ceramic was synthesized by conventional solid-state reaction method. Single phase of ceramic material was confirmed by XRD analysis. Rietveld refinement of XRD data shows that the sample has tetragonal phase having space group P4/mmm. Surface morphology was analyzed by scanning electron microscopy (SEM) shows grains were random and irregular in shape. In the dielectric properties, the effect of frequency and temperature on dielectric constant was investigated. The substitution of V ion on B site decreases the Curie temperature than pure BaTiO3. Theoretical fitting of Curie–Weiss law and Power law of dielectric data was confirmed the diffused phase transition in ceramic material. Doping of V in BZT has ferroelectric character with large value of remnant polarization, coercive field and Pr/Ps ratio. The results shows that the studied composition is suitable for capacitor applications.

Ti/Al/Ni/Au (30/120/20/100 nm) non-alloyed ohmic contacts on reactively ion-etched n-GaN have been obtained by thermal annealing in N2 + O2 ambient prior to metal contacts deposition. After surface treatment, contacts show the linear current–voltage (I–V) characteristics with specific contact resistance (SCR) of 2.91 × 10−5 Ω-cm2 without any post-deposition annealing, whereas, SCR of untreated sample has been found 1.02 × 10−4 Ω-cm2. The improvement in SCR of Ti/Al/Ni/Au contacts with this process may be attributed to formation of n+-highly doped layer due to presence of oxygen during thermal annealing. A further increase in SCR of non-treated sample from 1.02 × 10−4 Ω-cm2 to 3.54 × 10−4 Ω-cm2, has been observed on further annealing of contacts at 550 °C in N2 + O2 ambient for 5 min, which is generally an essential condition for formation of low-resistance highly transparent p-contact on p-GaN during fabrication of conventional GaN light-emitting diodes (LEDs). Based on X-ray photoelectron spectroscopy results, we found that there is increase in Ga 3d photoelectron binding energy with this surface treatment, which indicates a shift of Fermi level closure to conduction band, resulting in decrease of Schottky barrier height (SBH). The reduction in SBH is responsible for formation of low-resistance Ohmic contacts on n-GaN. Such non-alloyed n-contacts formed on thermally annealed reactively etched n-GaN surface may open for fabrication of more efficient conventional GaN LEDs. In addition, the forward voltage of GaN LED fabricated by present suggested process lowered by an amount of 0.37 V at 100 mA compared to standard process.

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.

Glass samples with compositions xSm2O3- (100−x)[0.1BaO–0.4ZnO–0.5B2O3]; x = 0.5, 1.0, 1.5 and 2.0 have been prepared using melt quench technique. Optical absorption and fluorescence spectra have been recorded for prepared glass samples at room temperature. The spectral intensities of Sm3+ transition observed in absorption spectra have been calculated by using Judd–Ofelt theory. The intensity parameters (Ω2, Ω4 and Ω6) have been estimated by applying least square fit method on the experimental (fexp) and calculated (fcal) oscillator strengths. The variation of Ω2 observed with the increase in Sm3+ ion concentration, is attributed to decease in covalency of rare earth oxygen bond due to change in optical basicity of host glass matrix. From the fluorescence spectra, four emission spectral lines have been observed that correspond to the transition from 4G5/2 ground state to lower lying 6H5/2, 6H7/2, 6H9/2 and 6H11/2 states with an excitation wavelength of 402 nm. The intensity parameters and the emission measurements have been used to estimate the various radiative parameters such as transition probabilities (AR), radiative lifetime (τR), branching ratio (βR) and stimulated emission cross-sections (σe) of luminescent levels. The value of σe is found to decrease with increase in concentration of Sm3+ ions and it possesses higher value for glass sample with x = 0.5 for transition lying in the visible region indicating its importance for photonic applications.

The ac conductivity of zinc modified tellurium based quaternary glasses having composition 60 TeO2–10 B2O3–(30 − x) Bi2O3–x ZnO; x = 10, 15, 20, 25 and 30 has been investigated in the frequency range 10−1–105 Hz and in temperature range 483–593 K. Frequency and temperature dependent ac conductivity found to obey Jonscher power law modified by Almond–West. DC conductivity, crossover frequency and frequency exponent have been estimated from the fitting of the experimental data of conductivity with Jonscher power law modified by Almond–West. The ac conductivity and its frequency exponent have been analyzed by various theoretical models. In presently studied glasses ac conduction takes place via tunneling of overlapping large polaron tunneling. Activation energy is found to be increased with increase in zinc content and dc conduction takes place via variable range hopping proposed by Mott with some modification suggested by Punia et al. The value of the stretched exponent (β) obtained by fitting of $$ M^{{\prime \prime }} $$ reveals the presence of non-Debye type relaxation. Scaling spectra of ac conductivity and electric modulus collapse into a single master curve for all compositions and temperatures, reveals the presence of composition and temperature independent conduction and relaxation process in these glasses. Activation energy of conduction (W) and electric modulus (E R ) are nearly equal, indicating that polaron have to overcome the same energy barrier during conduction as well as relaxation processes.

Iron doped barium calcium titanate (BCT) ceramics with compositions Ba 0.90 Ca 0.10 Ti 1−3 x /4 Fe x O 3 were prepared by a solid state reaction method. Pure perovskite tetragonal structure was confirmed by X-ray diffraction (XRD) analysis which is in coherence with the results obtained by Rietveld refinement. Relative density has been found above 90 percent. Tetragonality has been observed to decrease with Fe 3+ ion substitution for Ti 4+ .The dielectric properties of all the ceramic samples investigated as a function of temperature and frequency reveal that the transition temperature ( T c ) decreases on doping of iron content from 396 K to 349 K and an appreciable decrease in dielectric loss is observed on addition of Fe 3+ ions to BCT ceramics. The fitting of experimental data of dielectric constant ( e ′) with Curie Weiss Law and Power Law confirms the presence of first order transitions and diffusive behavior of the studied compositions. With increase in Iron content, the room temperature e ′ is observed to increase from 1450 to 2199 whereas, room temperature tan δ decreases from 0.024 to 0.009.The temperature coefficient ( T cc ) has also been calculated for all the samples. These studies suggest the application of prepared ceramic compositions for capacitor applications at room temperature and actuators.

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.

Er2O3 doped Barium-Zinc-Borate glasses with compositions xEr2O3-(100-x)[0.1BaO-0.4ZnO-0.5B2O3]; x = 0.5, 1.0, 1.5 and 2.0 have been prepared by melt quench technique. The amorphous nature of glasses has been ascertained by X-ray diffraction patterns. Fourier Transform Infrared (FTIR) spectra of the prepared glasses indicate that Er2O3 acts as glass modifier. With the increase in Er2O3 content, BO4 structural units start converting into BO3 structural units. The values of optical energy band gap (Eg) are observed to decrease with the increase in Er2O3 content. The values of nonlinear absorption coefficient (β) and nonlinear refractive index (n2) have been estimated by fitting of experimental data with theoretical models and both are found to increase with the increase in Er3+ ions concentration at 532 nm as well as 1550 nm excitation wavelengths. The calculated values of total third order nonlinear susceptibility (χ(3)) are observed to increase with the increase in Er3+ ions concentration.

BaZr0.045(Mn0.03Ti0.97)0.955O3(BZMT) ceramic was prepared via mixed-oxide solid state reaction method. XRD technique confirmed formation of single phase crystalline material. Rietveld refinement of XRD data revealed that the material has tetragonal phase with space group P4mm. The scanning electron microscope (SEM) investigation shows that grains are dense and irregular. The dielectric properties were study as a function of frequency and temperature. The relaxation mechanism was found thermally activated with activation energy 1.21eV and follows Arrhenius law. Modified ceramic showed ferroelectric properties with a high remnant polarization, saturation polarization and coercive field and Pr/Ps ratio.

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 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.

In the present manuscript, we have reported the structural, ac conductivity, dielectric studies and modulus formulation of Zn$_{1-x}$Ni$_x$O $(x=0.00,0.10,0.20,0.30)$ nanoparticles synthesized by sol-gel technique. The Rietveld refinement of X-ray powder diffraction data reveals that the samples possess hexagonal structure (space group - P63mc) of ZnO. The low intensity diffraction peaks corresponding to NiO comes into existence, it is suggested that phase segregation has occurred in the Ni doped ZnO nanoparticles. Average crystallite size has been estimated from XRD patterns, which is found to increase with increase in Ni content. AC conductivity and dielectric properties of Ni doped ZnO nanoparticles have been studied as a function of frequency (100 Hz to 10 MHz) of the applied ac signal in the temperature range of 323K to 463 K. The results showed that ac conductivity increases while other parameters such as the real dielectric constant $\varepsilon'$ and dielectric loss $\tan\delta$ decreases with frequency of applied field. The values of parameters $\varepsilon'$, $\tan\delta$ and ac conductivity are found to increase with increase temperature. In all the samples small polaron conduction mechanism is predominant. The variation of $\varepsilon'$, $\tan\delta$ and ac conductivity is observed to increase with increase in Ni dopant concentration in ZnO. The results of electrical modulus to study the relaxation dynamics of charge carriers indicate the presence of non-Debye type of relaxation in present samples.

Samarium oxide doped Barium–Zinc–Borate glasses with compositions xSm2O3−(100−x)[0.1BaO–0.4ZnO−0.5B2O3]; x = 0.0, 0.5, 1.0, 1.5 and 2.0 have been prepared by melt quench technique. The amorphous nature of as-prepared glasses has been ascertained by X-ray diffraction patterns. The observed values of density and molar volume of the glass samples are found to increase with the increase in concentration of Sm2O3. Fourier Transform Infrared spectra of the prepared glasses indicate that Sm2O3 acts as glass modifier. With the increase in Sm2O3 content, BO4 structural units start converting into BO3 structural units. The values of optical energy band gap (Eg), estimated from Tauc's plots, are observed to decrease with the increase in Sm2O3 content. The nonlinear optical properties of glass samples have been investigated by Z-scan method with nanosecond pulsed laser at ∼532 nm in both open and close aperture geometries. The values of two photon absorption coefficient (β) and nonlinear refractive index (n2) have been estimated by fitting of experimentally observed data with theoretical models and both are found to increase with the increase in Sm3+ ions concentration in the glass matrix. The total third order nonlinear susceptibility (χ(3)) have been calculated and observed to increase with the increase in Sm3+ ions concentration.

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.

Nd 3+ ions doped Barium–Tellurite–Borate glasses with compositions x Nd 2 O 3 − (100 − x )[0.1BaO–0.4TeO 2 –0.5B 2 O 3 ]; x = 0.0, 0.5, 1.0, 1.5 and 2.0 have been prepared by melt-quench technique. The amorphous nature of as-prepared glasses has been confirmed by X-ray diffraction patterns. The density, molar volume and equivalent crystalline volume of the glass samples have been found to increase with the increase in concentration of Nd 2 O 3 . FTIR and Raman spectra of the prepared glasses indicate that Nd 2 O 3 acts as glass modifier and as the content of Nd 2 O 3 increases, BO 4 structural units are converted into BO 3 structural units. The values of optical band gap have been estimated from the fitting of Mott and Davis’s model with the experimentally observed absorption spectra. The experimentally observed spectra of absorption coefficient also show good agreement with the hydrogenic excitonic model and the values of different parameters like optical band gap, excitonic binding energy, line width of m = 1 state and line width of continuum have been estimated from theoretical fitting of this model. The values of optical band gap are observed to decrease with increase in concentration of Nd 2 O 3 .

Glass samples with composition (70B2O3–29Bi2O3–1Dy2O3) modified with Barium titanate (BT), where BT is added in different successive weight percents, have been synthesized by conventional melt quenching technique. X-ray diffraction studies were performed in order to confirm the amorphous nature of the samples. The density of the samples has been found to decrease with an increase in the BT content, whereas an opposite trend has been observed in the molar volume. The analysis of FTIR and Raman spectra of the samples depicts that the glass network is built up of mainly BiO6, BiO3, BO3 and BO4 units. Its detailed analysis also revealed that the glass structure depends upon the amount of BT in the glass matrix and hence it acts as a modifier in the glass network. Introduction of BT into the glass matrix leads to the conversion of BO3 trigonal units into BO4 tetrahedral units, which results in a decrease in the degree of disorder in the glass network and makes the glass system more stable. The values of Urbach energy obtained for the prepared samples also confirmed the decrease in disorder in the glass network. The optical absorption measurements carried out for well-polished samples show a decrease in optical band gap energy with an increase in BT content whereas the molar refractivity shows the reverse trend. The Hydrogenic excitonic model applied to the studied glasses suggested that the present glass system favors direct transitions. The metallization criterion of the presently studied samples suggests that the prepared glasses may be potential candidates for nonlinear optical applications.

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.

Glasses with composition xLi2O-(50–x)Bi2O3-10ZnO-40B2O3 have been prepared by conventional melt quenching method. Density and molar volume decrease with increase in Li2O content. The IR and Raman studies indicate that these glasses are made up of [BiO3] [BiO6], [BO3] and [BO4] basic structural units. Li2O acts as a network modifier and modifies the glass structure. The optical absorption studies reveal that optical band gap decreases with Li2O content whereas Urbach energy (ΔE) shows an increasing trend. The metallization criterion is found to be in the range 0.368-0.386, indicating the suitability of these glasses for non-linear optical properties.

In this present work, CaCu3Ti4O12 (CCTO) was synthesized by conventional solid-state reaction technique. The synthesis process was carried out in two phases; by conventional process (calcination and sintering at 1080°C for 10 hours) and phase II involves the micro assisted pre sintering of conventionally calcined CCTO for very short soaking time of 30 min at 1080°C in a microwave furnace followed by sintering at 1080°C for 10 hours in conventional furnace. X-ray diffraction (XRD) patterns confirmed the formation of single phase ceramic. Dielectric properties were studied over the frequency range from 50Hz -5MHz at temperatures (273K-343K). It was observed that pre- microwave sintering enhance the dielectric constant values from 10900 to 11893 and respectively reduces the dielectric loss values from 0.49 to 0.34 at room temperature(1 KHz). CCTO ceramics which are found desirable for many technological applications. The effect is more pronounced at low frequencies of applied electric field.

Heavy metal-based oxide glasses of compositions xFe2O3.(40-x)PbO.60B2O3 have been synthesized by the standard melt-quenching technique. The amorphous nature of these samples is ascertained by XRD patterns. Scanning Electron Microscope is used to study the microstructure of the samples. The absorption edge (λcut-off) shifts toward longer wavelengths with an increase in Fe2O3 content in the glass matrix. Study of absorption edge signifies the glassy nature of the samples. The values of optical band gap energy for indirect allowed and forbidden transitions have been determined and it is found that it decreases with increasing Fe2O3 content. The Urbach’s energy is used to characterize the degree of disorder in the studied samples.

The structural, morphology, optical, electrical, and magnetic properties of Zn0.7MnxNi0.3−xO (x = 0.05, 0.1, 0.15, 0.2) nanoparticles synthesized by sol–gel technique have been systematically investigated by using X-ray diffractometer (XRD), scanning electron microscope (SEM), UV–vis-NIR spectrophotometer, impedance analyzer, and vibration sample magnetometer (VSM). XRD patterns reveal that all samples have hexagonal wurtzite structure along with secondary phases such as NiO and ZnMnO3. The average crystalline size increases with the increase in the Mn concentration in the host matrix. Diffuse reflectance studies (DRS) show an increment in optical band gap with increasing Mn content. AC conductivity of present samples has been studied as a function of frequency (100 Hz–10 MHz) of the applied AC signal in the temperature range of 323–463 K. The results showed that AC conductivity increases with an increase in frequency and temperature. The frequency exponent shows that small polaron conduction mechanism is the most favorable for all samples. The value of AC conductivity is observed to decrease with an increase in the Mn dopant concentration in the Zn0.7MnxNi0.3−xO system. At room temperature, magnetic characterization of the samples indicates the presence of both paramagnetic and ferromagnetic behavior. Magnetic saturation decreases with the increase in the Mn concentration in the host lattice.

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.

We systematically studied the effect of thermal annealing on the optical and electrical properties of amorphous semiconducting thin films in the system Ge20Te80−xBix (x = 0, 0.19, 2.93, 7.35) prepared by flash evaporation in a vacuum of 1 × 10−6 Torr. The films are characterized by x-ray diffraction (XRD) and electron probe micro analysis. The annealing temperature is kept at 150 °C, 180 °C and 220 °C. No crystallization of the thin films is achieved on annealing up to the temperature of 150 °C. At a higher temperature of annealing, microcrystals of Te, Bi2Te3, Ge–Te, etc, are observed along with an amorphous phase as indicated by XRD analysis. The fundamental optical absorption edge and reflection spectra of as-prepared and annealed films are determined. Optical interband transitions are observed for various films (as-prepared and annealed). The presence of crystalline Bi2Te3 in films annealed at 220 °C is also supported by the reflection spectrum. The optical energy gap (Eg), the slope parameter (Δ) of the absorption edge and the tailing parameter (B−1) of the energy band tails are computed from the optical data. The dc electrical conductivity (σdc) of various films is studied in the temperature range of 150–450 K. We observe that two types of conduction take place: conduction through extended states in the higher temperature region, and conduction through localized states in the band tails and at the Fermi level by the hopping process assisted by phonons at lower temperatures. The data at higher temperatures have been fitted with the expression σdc = σ0exp(−ΔE/kT) and the electrical parameters, ΔE and σ0, are also determined. It is observed that the bismuth concentration and annealing temperature dependences of the optical and electrical parameters are different in the two regions of compositions, x ≤ 2.93 and x > 2.93, indicating structural differences in the two sets of compositions. It is pointed out that the bulk form of these amorphous semiconductors exhibits a carrier sign reversal at a bismuth concentration of about 3.5 at%. However, the thin-film form of these amorphous semiconductors does not show such a carrier sign reversal in the electrical transport.

Bulk amorphous chalcogenide semiconductor, As2Se3, has been irradiated at room temperature with 75 MeV energy Ni, Ge and Ag ions at fluences in the range 1×10 13 –1×10 14 ions/cm 2 . The ion-induced effects on the electronic properties have been monitored by measuring the dc conductivity and frequency dependent ac conductivity (500 Hz – 10 kHz) as a function of temperature (180–450 K). It is found that the electrical effects in the samples bombarded with Ni ions are quite different from the ones bombarded with Ge/Ag ions. Ion-irradiation induced defect states near the Fermi level play a dominant role in the variable range hopping conduction. Bipolaron hopping conduction appears to be affected less by ion-irradiation. It is interesting to see that as small an ion-dose as 5×10 13 ions/cm 2 is quite effective to modify the electrical transport behaviour of the glass.