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In this study, Ba2Fe1−xNixMoO6(0.0 ≤ x ≤ 0.2) (BFNMO) double perovskite materials were prepared by sol–gel method in the H2/Ar atmosphere. The cubic structure of BFNMO was identified by XRD studies. The values of lattice parameters were marginally improved by Ni dopant. The saturation magnetization was set up to be abridged at temperatures 5 and 300 K by doping Ni in Ba2FeMoO6. The Curie temperature of BFNMO was also somewhat amplified by Ni content. The magnetoresistance studies of BFNMO showed up different behaviors at temperatures 5, 150, and 300 K with Ni composition. The value of magnetoresistance rose at 300 K and decreased at 5, 150 K by doping Ni in Ba2FeMoO6. The high value of MR (%) is − 16.75 for composition x = 0.0 at temperature 5 K and magnetic field 80 kOe in the BFNMO.

Ba2Fe1−xAlxMoO6(0.0 ≤ x ≤ 0.15)(BFAMO) double perovskite materials were synthesized by sol–gel technique in H2/Ar atmosphere. Unit cell volumes from lattice parameter of BFAMO were evaluated from the data obtained from X-ray diffraction studies. The prepared BFAMO samples show cubic crystal structure and the values of lattice parameters slightly increased by doping Al. The saturation magnetization (Ms) has been calculated by magnetization studies done at 5 and 300 K for BFAMO. The saturation magnetization was found to decrease at temperatures 5 and 300 K by doping Al in Ba2FeMoO6. The Curie temperature of BFAMO slightly increased by increasing Al content. The value of magnetoresistance (MR%) decreases at temperature 5, 150, and 300 K when doped with Al in Ba2FeMoO6. It is observed from magnetoresistance study results that the maximum value of MR (%) is − 16.75 for Ba2FeMoO6 at temperature 5 K and at magnetic field 80 kOe in the BFAMO.

Non-stoichiometric SrBaFexMo2−xO6 (SBFMO) (x = 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, and 1.4) double perovskite substances were synthesized by sol–gel process. Cubic structure was found by X-ray diffraction results for all samples of SBFMO. The degree of ordering (µ) of SBFMO was calculated theoretically. It is known that the degree of ordering (µ) is maximum for composition x = 1, in these substances. The electrical resistivity of SBFMO was found to increase when composition deviates from x = 1. The maximum value of saturation magnetization (MS) was obtained for composition x = 1 at temperature 5 and 300 K in the SBFMO series. A maximum value of − 28.27 of MR (%) is observed in the present SBFMO series for x = 1 at temperature 5 K and magnetic field 80 kOe. It was found from this study that there is a clear and perceptible relationship between lattice parameters, maximum degree of ordering (µ), saturation magnetization (MS), and magnetoresistance (MR %) among the series of samples. All of them showed a higher value of above characteristics at x = 1 and the values decline as composition (x) deviated from unity in SBFMO.

Effect of Ga addition on structure, resistivity and magnetoresistance of Ba2Fe1−xGaxMoO6 (x = 0.0, 0.1, 0.25 and 0.3) double perovskite. The sol–gel procedure was used to synthesize Ba2Fe1−xGaxMoO6 double perovskite and consolidated at 1150 °C under Ar/H2 atmosphere. Single phase with cubic crystal structure confirmed for all the samples through X-ray diffraction studies. Variation of grain size behavior on the samples surface has been studied by scanning electron microscopy (SEM). The spectra from energy dispersive X-ray spectroscopy (EDS) showed that all the elements Ba, Fe, Ga, Mo and O are present in the samples and there are no impurities in the materials. Fourier transform infrared spectroscopy (FTIR) spectral analysis of samples produced three characteristic absorption bands of Mo–O and Fe–O vibrations in the wave number range 400–1000 cm−1 which confirmed the present materials are double perovskite phase. Magneto-resistance (MR %) of these samples reduce with the addition of Ga content at room temperature (RT). Whereas, MR% at 5 K exhibits opposite trend to the MR% at RT with the Ga-content. It is found that all samples show semiconductor behavior at 5 K and changes into metallic nature as temperature increases showing a semiconductor-metallic transition. This value is larger for composition x = 0.3 and smaller for parent compound.

Synthesis of Sr2FexMo2−xO6 (x = 0.8 to 1.5 with a step increment of 0.1) (SFMO) double perovskite oxides were done by sonochemical method at relatively low preparation temperature (950 °C). Purity and existence of all elements (Sr, Fe, Mo, and O) in SFMO compound have been analyzed by energy dispersive X-ray spectroscopy (EDS). Lattice parameters and unit cell volume were studied by X-ray powder diffraction (XRD). The structural transition from tetragonal to cubic occurs around composition x = 1.1 has been noticed from XRD data. Scanning electron microscopy (SEM) confirmed grain sizes of SFMO series, which are found to be in the range of 75–185 nm. Perovskite formation has been confirmed by Fourier transform infrared spectroscopy (FTIR) spectrum analysis. Investigations of Magnetic properties have been carried out using Vibrating Sample Magnetometer (VSM) at applied magnetic field from − 20 to + 20 kOe. Saturation magnetization is found to increase from x = 0.8 to 1 and then decreases from x = 1 to 1.5, the behavior is correlated with degree of Fe/Mo ordering.

Characterization, Fe/Mo ordering and magnetic properties of Ca2FexMo2−xO6 (x = 0.9, 1.0, 1.1 and 1.2) (CFMO) double perovskite have been studied. Sonochemical methodology is adopted to synthesize Ca2FexMo2−xO6 double perovskite at low temperature (950 ∘ C) under Ar/H2 atmosphere. Single-phase monoclinic structure by space group P21/n, lattice parameters (a, b and c) and unit cell volume (V ) have been confirmed from X-ray diffraction (XRD) patterns. Average grain sizes of 145 nm with a variation of porosity were observed from scanning electron microscopy (SEM) pictures. Elemental analysis using energy-dispersive X-ray spectroscopy (EDS) confirmed the presence of elements Ca, Fe, Mo and O with no trace of foreign elements, and the compound is found to be pure. Fourier transform infrared spectroscopy (FTIR) data confirmed perovskite formation by identifying three characteristic absorption bands in the wave number range 400–1000 cm− 1 for Mo-O and Fe-O vibrations. Magnetic properties like Ms, Mr and Hc were studied for CFMO series using vibrating sample magnetometer (VSM). Saturation magnetization is found to vary with Fe composition (x).

Double perovskite materials Sr2Fe1 − xInxMoO6 (x = 0.0 and 0.2) were synthesized by sol–gel process. The materials were analyzed by X-ray diffraction and it is found that perovskite material crystallized in tetragonal structure, with space group I4/mmm. Variation of porosity and grain size behavior of samples has been studied by scanning electron microscopy. The spectra from energy dispersive X-ray spectroscopy showed that all the elements Sr, Fe, In, Mo and O are present in the samples and there are no impurities in the materials. Fourier transform infrared spectroscopy spectral analysis of present samples produced three characteristic absorption bands of Mo–O and Fe–O vibrations in the wave number range 400–1000 cm− 1 which confirmed the present material is double perovskite phase. From electron spin resonance spectra, it is found that the value of g ~ 2.00 and indicates that Fe is in 3 + ionic state in these materials. It was found from conductivity results that conductivity of indium doped sample reduced when compared with parent compound Sr2FeMoO6. Indium doped sample showed semiconductor behavior whereas parent sample showed semiconductor–metallic behavior from 5 to 300 K. The electrical conductivity of the materials increases with increase of magnetic field at constant temperatures 5, 150 and 300 K. Magnetoresistance (%) of the present materials increases with magnetic field range from 0 to 4 T and decreases with temperature from 5 to 300 K. Magnetoresistance (%), saturation magnetization and transition temperature of indium doped material has lesser value compare to Sr2FeMoO6.

Double perovskite oxide Ba2CeZrO6 is synthesized by sol–gel technique for the first time. The X-ray diffraction pattern at room temperature show that the sample exists in single phase and crystallizes in cubic structure with space group $$Fm\stackrel{-}{3}m.$$ The lattice parameter is found to be 0.8635 nm. A scanning electron micrograph image of the Ba2CeZrO6 sample show uniform distribution of grains size ranging from 2.4 to 3 μm. EDAX spectra showed that Ba2CeZrO6 sample contains only Ba, Ce, Zr and O elements which are closer to stoichiometric ratio. Fourier transform infrared spectra of Ba2CeZrO6 showed the peaks observed corresponds to CeO6 and ZrO6 octahedra indicates the formation of double perovskite structure. The tolerance factor (t) of Ba2CeZrO6 sample is 0.90 suggests unit cell has a small distortion from ideal cubic structure. Frequency (100 Hz–5 MHz) dependent impedance spectroscopy studies were carried out at different temperatures ranging from room temperature to 400 °C. The decrease in impedance (Z), relaxation time (τ) and grain, grain boundary resistance and increase in conductivity with increase in temperature shows the semiconducting nature of the Ba2CeZrO6 sample. Nyquist analysis showed the contribution of grain and grain boundary resistances for the relaxation process in Ba2CeZrO6 sample. The relaxation mechanism in the sample is found to be independent of temperature. The activation energy of Ba2CeZrO6 sample is found to be 0.38 eV.

The chemical composition of (SiO2)59.9 – (PbO)30 – (Pr2O3)0.1 – (Sb2O3)x: (Al2O3)y – x have chosen for present glass synthesis, where the variable ‘x’ varies from 0 to 10 mol% and againstly ‘y’ varies from 10 to 0 mol% with a step size of 2 mol%. The samples were characterized by structural, photo and thermoluminescence techniques. The evolutions of thermal stability, elastic modulus, micro hardness and glass transition quantities advised that they are mechanically hard in nature. The γ - irradiated trap-depth parameters such as A.E. (~0.371eV) and shape symmetry ratio (~0.236) related to the thermoluminiscence characterization advised that the sample code ‘PAS6’ is a useful TL asset. The Judd - Ofelt quantities are derived from optical absorption spectra such as Ω2, Ω4 and Ω6 are found to be best for the glass code ‘PAS6’ (~8.64, ~4.65 and ~3.88 × 10−20 cm2) is a useful optical resource. Radiative parameters derived from photoluminescence characterization such as spectroscopic quality factor (~1.198), effective bandwidth (Δλ ~ 32 nm), transition probability (At = 1271 s−1), stimulated emission cross section (σ = 1.321 × 10−20 cm2), branching ratio (β ~ 49%) and radiative life time (τrad = 217 μs) are advising that the sample code ‘PAS6’ is a useful luminescent resource for various optical applications.

Double perovskite oxides Sr2 Fe x Mo2−x O6 (x = 0.8, 1.0, 1.2, 1.3 and 1.4) (SFMO) of different compositions were prepared by sol–gel growth followed by annealing under reducing atmosphere conditions of H2/Ar flow. X-ray powder diffraction studies revealed that the crystal structure of the samples changes from tetragonal to cubic at around x = 1.2. Lattice parameters and unit cell volume of these samples found to decrease with the increase in Fe content. The characteristics absorption bands observed in the range 400–1000 cm−1 of Fourier transform infrared spectra indicate the presence of FeO6 and MoO6 octahedra and confirm the formation of double perovskite phase. The value of g ∼ 2.00 obtained from electron spin resonance studies indicates that Fe is in 3+ ionic state in the SFMO samples. Dilatometric studies of these samples reveal that the average value of coefficient of thermal expansion ( $ {\overline {\alpha }}$ ) increases with the increase in temperature or Fe content in SFMO samples. The low value of coefficient of thermal expansion 1.31 × 10−6 ∘C−1 obtained for Sr2Fe0.8Mo1.2O6 in the present study in the temperature range of 40–100∘C makes it useful as anode material in fuel cells. The coefficient of thermal expansion ( $ {\overline {\alpha }}$ ) and the unit cell volume (V) of SFMO samples vary inversely with composition in agreement with Gruneisen relation.

Sr 2 Fe x Mo 2− x O 6 ( x = 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4 and 1.5 wt.%) (SFMO) double perovskite oxides of different compositions have been prepared by sol–gel method. These materials were subjected to X-ray diffraction and found that crystal structure changes from tetragonal to cubic around x = 1.2 wt.%. Lattice parameters and unit cell volume have been calculated using X-ray diffraction data. Magnetization studies have been carried out using Vibrating Sample Magnetometer ranging from −15 kOe to +15 kOe and saturation magnetization ( M s ) has been determined. Electrical resistivity and magnetoresistance studies have been carried out in the magnetic field range of −40 kOe to +40 kOe keeping the temperature constant at 5, 150 and 300 K using standard four-probe method. Resistivity studies have also been carried out in the temperature ranging from 5 to 300 K keeping the magnetic field constant at 0, 10, 20 and 40 kOe. Maximum degree of Fe/Mo ordering ( η max ) of SFMO has been calculated and compared with magnetic and transport properties. It has been found that there is a strong correlation between 3 parameters η max , M s and MR (%), i.e. all of them show a maximum at x = 1.0 wt.% and decreases as x deviates from 1.0 in SFMO. It has been also found that there is a different resistivity behavior between x ≤ 1.2 wt.% and x > 1.2 wt.% samples of SFMO. Semiconductor metal transition temperature was found to be maximum at x = 1.0 wt.%.

A series of Sr 2 Fe 1− x In x MoO 6 ( x = 0, 0.1, 0.3 and 0.4 wt.%)(SFIMO) double perovskite oxide powders were prepared by sol–gel method. The materials were subjected to X-ray diffraction and found to crystallize in tetragonal structure with space group I 4/ mmm . Lattice parameters and unit cell volume were calculated using X-ray diffraction data. It was found that the tetragonal distortion ( c / a 2 ) increases while the deviation of the tolerance factor from unity increases with increase of indium composition in SFIMO samples. Magnetization studies were carried out using vibrating sample magnetometer (VSM). It has been found that the saturation magnetization ( M s ) and remanent magnetization ( M r ) decreases while coercivity ( H c ) increases with increase of indium composition in SFIMO samples. Electrical resistivity and magnetoresistance studies in the magnetic field range from −40 kOe to 40 kOe were carried out keeping the temperature constant at 5, 150 and 300 K using standard four-probe method. Resistivity studies were also performed in the temperature range from 5 to 300 K keeping magnetic field constant at 0, 10, 20 and 40 kOe. The resistivity studies showed that the magnitude of magneto resistance (MR%) decreases with increase of temperature from 5 to 300 K while the value of MR (%) is found to increase with increase of magnetic field. The MR (%) was found to decrease with increase of indium concentration in SFMIO compounds. The degree of ordering, M s and MR (%) agreed well with each other.

Zinc bismuth borate glasses with composition 10ZnO–xBi2O3–(90 − x)B2O3 (where x is in mol%, ranging from 25 to 50 in steps of 5) have been prepared using conventional melt quenching technique. Differential scanning calorimetry (DSC) studies showed that the glass transition temperature (Tg) decreases from 473 °C to 449 °C as the content of Bi2O3 increases. The optical absorption studies revealed that the cutoff wavelength increases while optical band gap energy (Eopt) and Urbach energy (ΔE) decreases with increase of Bi2O3 content. The Eopt values of these glasses are found to be in the range 3.464–3.169 eV where as the values of ΔE lies in the range 0.503–0.178 eV. The DSC and optical absorption studies revealed that the glass network becomes less tightly packed and degree of disorder increases with increase in Bi2O3 concentration in the present glass system. The IR studies indicate that these glasses are made up of [BiO6], [BO3] and [BO4] basic structural units. The values of optical basicity evaluated using oxide ion polarizability α b 2 − ( E opt ) obtained from optical band gap are in agreement with those values calculated from optical basicity values of the constituent oxides.

Double perovskite oxides of Sr2Fe1-xInxMoO6 (x = 0.0, 0.1 and 0.4 wt. %.) were prepared by sol-gel growth followed by annealing under reducing atmosphere conditions of 10% H2/Ar flow. These samples were characterized by X-ray diffraction, Scanning Electron Microscopy and Electron Spin Resonance studies. High temperature thermal expansion studies were carried out using Netzsch 402PC dilatometer in the temperature range from 40 to 400°C. The coefficient of thermal expansion (α) was calculated at different temperature for all the samples. The value of α was found to increase with increase of temperature while average value of coefficient of thermal expansion found to decrease with indium composition in SFIMO materials.

Different compositions of double perovskite oxide powders of Ba2Fe1-xGaxMoO6 (x=0.0, 0.1, 0.25 and 0.3) were prepared by sol-gel method. These materials were subjected to X-ray diffraction studies to confirm the crystal structure. Magnetization studies were performed using VSM and saturation magnetization found to decreases by addition of Ga. Electrical resistivity data were collected while varying magnetic field from 0 to 80 kOe keeping temperature constant at 150 K by four-probe method. Resistivity studies were also performed by varying temperature from 5 to 300 K keeping magnetic field constant at 0 and 80 kOe. Magneto resistance (MR%) was calculated using resistivity data. The MR (%) was found to increase with increase of Ga concentration in BFGMO compounds.