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A comprehensive study on structural, spectral, magnetic and dielectric properties of holmium substituted (Ho3+) lithium ferrites; Li1.2Co0.4HoxFe2−xO4 (x = 0.00–0.15) synthesized via auto-citric combustion route has been carried out. The annealing temperature essential for complete decomposition of precipitates and spinel phase formation was found around 950 °C which was estimated from thermo-gravimetric analysis (TGA). The development of face centered cubic (FCC) spinel structure was confirmed from X-ray diffraction (XRD) analysis. However, the traces of an ortho phase (HoFeO3) were appeared for x ≥ 0.06 indicating the solubility limit of Ho3+ ions. The lattice constant ′a′ increased from 8.351 to 8.360 A upon Ho addition up to x = 0.06 and it decreased thereafter from 8.360 to 8.352 A. This decrease in lattice constant was attributed to the secondary phase formation revealing segregation of Ho3+ ions at grain boundaries. The porosity was found to decrease from 44 to 23% by the inclusion of Ho3+ ions. Fourier transform infrared spectra (FTIR) exhibited tetrahedral (v1) and octahedral (v2) intrinsic vibrational bands at 627 cm−1 and 479 cm−1 respectively and these bands revealed a shift with increasing Ho concentration. The variations in force constants (Ko and Kt) were calculated and discussed with the tetrahedral (rA) and octahedral (rB) bond length trends. The dielectric parameters have been investigated as a function of composition and frequency. The systematic addition of Ho gradually increased the ac conductivity from 8.97 × 103 to 5.56 × 104 (Ω-cm)−1 up to x = 0.12 and it subsequently decreased for x = 0.15. The complex impedance examination (Cole-Cole plots) confirmed a grain-interior phenomenon, effectively contributing to the dielectric properties. The coercivity was enhanced while the saturation magnetization (Ms) was lessened by the incorporation of Ho3+ ions. The maximum value of coercivity (706 Oe) was obtained for Li1.2Co0.4Ho0.12Fe1.88O4. The improved coercivity may suggest their utilization in perpendicular recording media applications.

Ytterbium (Yb) doped X-type hexagonal nano-sized ferrites (Sr2NiCoFe28O46) were fabricated by micro-emulsion method. The development of hexagonal structure of ferrite materials was confirmed by XRD analysis. The size of crystallites as determined by Scherrer's formula was found in the range 29–41 nm. The lattice strain of these ferrites was increased from 3.62 × 10−2 to 3.73 × 10−2 with the increased Yb-contents. The tetrahedral absorption bands shifted slightly towards higher frequency whereas octahedral bands shifted towards lower frequency side. The incorporation of Yb enhanced dc electrical resistivity significantly from 2.05 × 108 to 3.35 × 109 Ω-cm. The AC conductivity was increased with frequency whereas it decreased with the inclusion of Yb3+ ions. This distinctive behavior of these hexagonal ferrites may be suitable for microwave devices and electromagnetic attenuation applications. The doping of Yb3+ optimized coercivity whereas remanence and saturation magnetization were decreased. These ferrite materials can be used in longitudinal recording media due to more thermally stable and higher coercivity (577–671 Oe).

A series of Dy-doped Li–Ni ferrites of the following composition Li 0.5 Ni 0.48 Tb 0.02 Dy x Fe 2−x O 4 (0.2≤x≥0) was synthesized by the microemulsion method. The X-ray diffraction (XRD) analysis indicated that Li 0.5 Ni 0.48 Tb 0.02 Dy x Fe 2−x O 4 nano-crystalline ferrites exhibited the single-phase spinel structure. The lattice parameter was determined by the Nelson-Riley refinement technique and it increased by increasing the Dy contents. The crystallite size was computed from the Debye Scherrer's formula and it was in range from 27 to 40 nm. The thermal decomposition process was studied by the thermogravimetric analysis and the annealing temperature observed was 980 °C. The real and complex parts of dielectric constant decreases very sharply in the lower frequency region, but in the higher frequency region, the real and complex part of dielectric constant show variable values with Dy contents. The dielectric tangent loss (tan δ) decreases exponentially with Dy contents. The magnitude of the ac conductivity decreases in certain frequency region, as the Dy contents are increased. The possible mechanisms contributing to the above behavior are discussed. The results of these nanocrystalline ferrites are very suitable materials for microwave device applications.

Nano-sized Zr-Co doped nickel ferrites with nominal composition, NiZr x Co x Fe 2-2x O 4 ( x =0.0, 0.2, 0.4, 0.6, 0.8) were synthesized using the micro-emulsion route. The structural elucidation of the synthesized materials was carried out by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. The XRD analysis confirmed face centered cubic (FCC) structure of all compositions of NiZr x Co x Fe 2-2x O 4 nanocrystallites. Crystallite size was calculated by Scherrer's formula found in the range 10–15 nm. The variation in lattice parameter as determined by XRD data agreed with size variation of host (Fe 3+ ) and guest (Zr 4+ and Co 2+ ) cations. FTIR spectra of doped NiFe 2 O 4 exhibited the typical octahedral bands at 528.4 cm −1 which is the characteristic feature of spinel structure of spinel ferrites. The characterized spinel NiZr x Co x Fe 2-2x O 4 nano-ferrites were evaluated for their potential applications by magnetic hysteresis loops and dielectric measurements. The value of saturation magnetization ( M s ) decreased from 47.9 to 13.09 emu/g up to x =0.8 with ups and downs fluctuations in between x=0.0 to x=0.8. The high values of Ms of some compositions predicted the potential applications in high density perpendicular recording media and microwave devices. The frequency dependent behavior of permittivity (e') is recorded and discussed with the help of hopping mechanism of both holes and electrons. The dielectric and magnetic data of NiZr x Co x Fe 2-2x O 4 nano-ferrites suggested the potential applications of these ferrite nanoparticles in high frequency and magnetic data storage devices fabrication.

New X-type hexagonal Yb3+-doped Ba2Co2Fe28O46 ferrites were prepared via wet chemical route. The Yb3+-contents in Ba2Co2YbxFe28−xO46 were kept from 0.00 mol to 0.15 mol in six different compositions. XRD patterns in two theta range 15–70 confirmed the X-type hexagonal ferrites with crystallite size

Gadolinium (Gd) and Dysprosium (Dy) co-doped Ni-Co (Ni 0.4 Co 0.6 Fe 2 O 4 ) ferrites were prepared by micro-emulsion route. X-ray diffraction (XRD) analysis indicated the development of cubic spinel structure. The lattice parameter and X-ray density were found to increase from 8.24 to 8.31 A and 5.57 to 5.91 (gm/cm 3 ) respectively as the Gd-Dy contents increased in nickel-cobalt ferrites. The crystallite size calculated from the Scherrer's formula exhibited the formation of nanocrystalline ferrites (13–26 nm). Two foremost absorption bands observed in FTIR spectra within 400 cm −1 (υ 2 ) to 600 cm −1 (υ 1 ) which correspond to stretching vibrations of tetrahedral and octahedral complexes respectively. The dielectric constant (e) and dielectric loss (tanδ) were decreased by the optimization of frequency and abrupt decrease in the low frequency region and higher values in the high frequency region were observed. The dielectric dispersion was due to rapid decrease of dielectric constant in the low frequency region. This variation of dielectric dispersion was explicated in the light of space charge polarization model of Maxwell-Wagner. The dielectric loss occurs in these ferrites due to electron hopping and defects in the dipoles. The electron hopping was possible at low frequency range but at higher frequency the dielectric loss was decreased with the decrease of electron hopping. Magnetic properties were observed by measuring M-H loops. Due to low dielectric loss and dielectric constant these materials were appropriate in the fabrication of switching and memory storage devices.

Graphene nanosheets fabricated with copper doped manganese ferrite nanoparticles and the resultant Mn 1-x Cu x Fe 2 O 4 /rGO nanocomposite was investigated as electrode material for supercapacitors. Copper doped manganese ferrite nanoparticles chemically anchored on graphene nanosheets exhibited the enhanced capacitive performance as compared to individual components due to the synergistic effect of faradic behavior and electric double layer capacitance. It is observed that the electrical conductivity of manganese ferrites was enhanced by the doping of conducting metal copper ions. Two-probe ( I-V ) measurements, assured the increased conductivities of copper doped manganese ferrites and Mn 1-x Cu x Fe 2 O 4 /rGO nanocomposite. Cyclic voltammetry experiments and electrochemical impedance spectroscopy confirmed the superior electrochemical activity of Mn 1-x Cu x Fe 2 O 4 /rGO nanocomposite. The fascinating electrochemical activity of nanocomposite makes it a potential candidate for supercapacitor applications.

Dy 3+ metal ions doped nanocrystalline lead zirconate perovskite with nominal composition Pb 1−1.5x Dy x ZrO 3 (x=0, 0.01, 0.02, 0.03, 0.04 and 0.05) were fabricated by wet chemical micro-emulsion technique. The annealing of all the samples was done at 700 °C for 3 h. The prepared nanocrystalline powder was characterized by different techniques such as X-ray powder diffraction (XRD), Fourier transforms infra-red spectroscopy (FTIR), dielectric response and dc-electrical resistivity. The powder XRD pattern confirmed the development of orthorhombic perovskite structure and the size of crystallite was calculated in the range of 45–135 nm. The lattice parameters and the crystallite size were demonstrated a nonlinear trend. The FTIR spectra were represented the intrinsic cation's vibration in the characteristic perovskite orthorhombic structure which observed in the range of 500−4000 cm −1 . The dielectric properties of all the prepared samples were measured in the range of 1×10 6 to 1×10 9 Hz at room temperature. The decreasing trend in dielectric characteristics was observed with the incorporation of Dy 3+ metal ions in PbZrO 3 and also in these dielectric parameters, the damping effect was observed due to the replacement of Pb 2+ ions with Dy 3+ ions in the region of higher frequency. The ac conductivity was measured in the range of 6.94×10 −5 –2.73×10 −5 (Ω cm) −1 by using dielectric results at 1.5 MHz frequency. Such results revealed that the ac conductivity have decreasing behavior with the doping of Dy 3+ ions in PbZrO 3 nanocrystals. The current voltage (I-V) measurements depicted the increase in DC-electrical resistivity with increase of Dy 3+ content in lead zirconate. The minimum and maximum resistivities were observed as 1.315×10 11 Ω cm for PbZrO 3 and 2.206×10 11 Ω cm for Pb 0.955 Dy 0.03 ZrO 3 nanocrystals, hence two fold increase in DC-electrical resistivity was found. The dominating influence of doping on dielectric and electric parameters is highly encouraging for the manufacturing of high frequency memory devices.

In the current investigation, graphene (rGO)-supported cerium substituted nickel ferrite (NiCe

La3+ ions substituted manganese ferrite (MnFe2-x La x O4) nanoparticles via reverse micelles strategy were synthesized and their structural and electrical properties are discussed in this article. Using low-cost precursors, mono-dispersed, and well crystalline MnFe2-x La x O4 nanoparticles were prepared at low temperature. X-ray diffraction (XRD) explored cubic spinel structure with minute secondary phase as LaFeO3. The crystallite size of MnFe2-x La x O4 was found to increase from 12.82 nm to 15.95 nm with increased La3+ ions contents. The room temperature Fourier transform infrared (FTIR) spectra were recorded in the wavenumber range 1000–400 cm−1 that showed the vibrational bands of octahedral and tetrahedral complexes. These bands are the fingerprints of spinel ferrites. Surface morphology characterized by field emission scanning electron microscopy (FESEM) revealed the relative spherical morphology of prepared spinel ferrite particles. The elemental composition analysis from Energy-dispersive x-ray (EDX) spectroscopy confirmed the presence of expected elements in the samples. The modification in resistivity and the enhancement in the dielectric parameters suggested the possible utilization of these soft ferrite nanoparticles in advanced electronics, especially the devices that are required to operate at high frequencies.

An electrode with a three-dimensional spatial framework, good electrical conductivity, higher specific surface area, porous structure, and binder-free design is considered to be most ideal for supercapacitor applications. It is a major challenge for the electrochemical researchers to manufacture an electrode material with a rational design that exhibits all of the above features. In this context, we have fabricated nanostructured Co3O4 and its nanohybrid with carbon nanotubes via a single-step hydrothermal route. A binary nanohybrid sample directly decorated on the three-dimensional nickel foam was used as a binder-free electrode for supercapacitor applications. Our electrode fabricated with multiple approaches showed an excellent specific capacitance of 852 Fg−1 @ 1 Ag−1 and the best rate capability of 89.7% @ 12 Ag−1. Moreover, the nanohybrid electrode possessed outstanding cyclic stability of 91.6% retention after 7000 Galvanostatic charge–discharge cycles. The superior electrochemical activity of the binary nanohybrid is benefiting from its porous nanostructure, hybrid composition, higher specific surface area (145 m2g−1), good electrical conductivity (3.3 × 10−2 Sm−1), and binder-free design. Application study results suggested that multiple approaches for preparing the supercapacitor electrode were constructive and encouraging.

In the current study, we have fabricated Mn-doped Co3O4 nanoparticles (Mn.Co3O4 NPs) and their binary nanohybrid with r-GO nanosheets (Mn.Co3O4/r-GO) and decorated it directly on the nickel foam (NF) via a single-step hydrothermal method. The Mn.Co3O4/r-GO nanohybrid exhibits excellent electrical conductivity (1.84 × 104 Sm−1) and a higher BET surface area (147 m2 g−1). The Mn.Co3O4/r-GO sample electrode shows an outstanding electrochemical activity and exhibits a gravimetric capacitance up to 932 Fg−1 @ 1 Ag−1. On increasing the current density from 1 to 5 Ag−1, the nanohybrid electrode retains 84.4% of its original capacitance (at 1 Ag−1), indicating its excellent rate capability. Moreover, the nanohybrid electrode reveals exceptional cycling stability as it lost just 7.3% of its original capacitance (at the 1st cycle) after 5000-cycling experiments. The tremendous electrochemical activity of the fabricated nanohybrid can be ascribed to the synergistic effect between the good crystallinity of its Mn.Co3O4 NPs and excellent conductivity of its r-GO nanosheets. The 3D nanostructure of the Mn.Co3O4/r-GO nanohybrid decorated directly on the NF shorter the ion diffusion path and exposes more active sites to achieve the superior gravimetric capacitance and higher rate capability. This study may offer the use of multi-approaches to engineer the novel 3D nanostructured electrode materials for electrochemical capacitors with excellent cyclic stability, good rate capability, and higher gravimetric capacitance.

Polycrystalline ErxNi0.8Zn0·2Fe2-xO4 nanoparticles were synthesized using wet chemical route. Powder x-ray diffraction (XRD) data was utilized to observe the structural parameters. The cubic crystalline structure with the second phase was obtained from XRD patterns. Two significant absorption bands (between 700 and 400 cm−1) at the tetrahedral and octahedral sites were studied from Fourier transform infrared spectroscopy (FTIR) that further confirmed the spinel structure of prepared ferrites. These are the main bands of spinel ferrites. After the structural explanation, the dielectric, electrical and magnetic parameters were studied in detail at room temperature. All of these parameters were affected by Er3+ substitution. The obtained results suggested the possible utilization of these soft ferrites in advanced technological applications such as the devices working at high frequencies, magnetic data recording, switching applications, etc.

An efficient, environment-friendly and economical catalyst to control contaminants of environment is an enduring interest in recent years. In this study, a new composite, DyxMnFe2-xO4nanoparticles decorated over mesoporous silica was synthesized and utilized for removal of organic pollutant. Highly crystalline nature of DyxMnFe2-xO4 nanoparticles and amorphous nature of material was confirmed by XRD (X-ray diffraction) technique. Infrared spectra of fabricated material before and after adsorption of dye molecules evidenced the successful adsorption of dye molecules by fabricated adsorbent. From field emission scanning electron microscopic (FESEM) images of Dy3+ substituted MnFe2O4 composite with mesoporous silica, it was clearly observed that ferrite particles of size 20-30 nm were decorated on the surface of mesoporous silica particles and distributed well over spherical silica balls homogeneously. Its magnificent mesoporous nature was revealed from BET (nitrogen adsorption-desorption measurements) analysis. Surface area, pore volume and average pore size was found 387.95 m2/g, 0.390 cm3/g and 4.02 nm respectively. Tri-modal pore size distribution showed its effective utilization in adsorption. The abundant (SiOH) hydroxyl groups of mesoporous silica, the broad diffraction hump of silica depicted its superior loading capacity of target molecular specie inside its porous network. From band gap analysis, a red shift of 2.43 eV exhibited semiconductor photocatalysis of DyxMnFe2-xO4 nanoparticles. Degradation efficiency of bare MnFe2O4, DyxMnFe2-xO4 and mesoporous silica-based composite was tested using crystal violet dye. Its explored adsorption-photocatalysis synergy, degradation mechanism, kinetic investigation, easily recovery and remarkable recycling ability suggested that the new fabricated composite is best for environmental remediation.

The influence of rare-earth metals (La, Nd, Gd, Tb, Dy) on morphology, Raman, electrical and dielectric properties of Ba2NiCoRExFe28−xO46 ferrites were studied. The scanning electron microscopy (SEM) exhibited the platelet like structure of these hexagonal ferrites. The surface morphology indicated the formation of ferrite grains in the nano-regime scale. The bands obtained at lower wave number may be attributed to the metal-oxygen vibration at octahedral site which confirm the development of hexagonal phase of these ferrites. The resonance peaks were observed in dielectric constant, dielectric loss factor and quality factor versus frequency graphs. These dielectric parameters indicate that these ferrites nano-materials are potential candidates in the high frequency applications. The enhancement in DC electric resistivity from 2.48×108 to 1.20×109 Ω cm indicates that the prepared materials are beneficial for decreasing the eddy current losses at high frequencies and for the fabrication of multilayer chip inductor (MLCI) devices.

A nanocomposite containing α-Fe2O3 nanoparticles entangled with reduced graphene oxide nanosheets have been synthesized via simple hydrothermal and ultra-sonication method. It is observed that graphene nanosheets enhanced the electrical conductivity and electrochemical activity of α-Fe2O3 nanoparticles. The superior electrical conductivity of α- Fe2O3/rGO nanocomposite was confirmed by two probe current-voltage (I-V) measurements. The enhanced electrochemical activity of α- Fe2O3/rGO nanocomposite was confirmed by electrochemical impedance spectroscopy measurements and cyclic voltammetry experiments. It is observed that as-prepared α- Fe2O3/rGO nanocomposite has superior charge-transfer resistance and higher specific capacitance than bare α-Fe2O3 nanoparticles. Moreover, nanocomposite retained 75% of the initial capacitance after 1000 cycles. Due to tremendous electrochemical performance, the α- Fe2O3/rGO nanocomposite have potential applications in energy storage devices.

Terbium (Tb) and dysprosium (Dy) doped lithium-nickel nano-sized ferrites (Li 0.2 Ni 0.8 Tb 0.5 x Dy 0.5 x Fe 2− x O 4 where x =0.00−0.08) were prepared by micro-emulsion technique. The X-ray diffraction (XRD) patterns confirmed the single phase cubic spinel structure. The lattice constant was increased due to larger ionic radii of Tb 3+ and Dy 3+ cations. The crystallite size was found in the range 30–42 nm. The FTIR (Fourier transform infrared spectroscopy) spectra revealed two significant absorption bands (~400–600 cm −1 ) which indicate the formation of cubic spinel structure. The peaking behavior of dielectric parameters was observed beyond 1.5 GHz. The dielectric constant and dielectric loss were found to decrease by the increase of Tb–Dy contents and frequency. The doping of Tb and Dy in Li–Ni ferrites led to increase the coercive field (120–156 Oe). The smaller magnetic and dielectric parameters suggested the possible utility of these nano-materials in switching and microwave devices applications.

A ternary nanocomposite of molybdenum trioxide (α-MoO 3 ) nanowires coated with a thin layer of carbon, which is intertwined with graphene oxide is synthesized by hydrothermal and ultrasonication route. It is found that high conductivity of carbon coated MoO 3 nanowires is further increased by introducing the graphene sheets. The ternary nanocomposite (rGO/MoO 3 @C) exhibits high specific capacitance, excellent cyclic stability compared to the carbon coated MoO 3 (MoO 3 @C) and virginal MoO 3 nanowires due to the synergistic effect of carbon layer and graphene. The electrochemical impedance measurements show that rGO/MoO 3 @C nanocomposite have lower charge transfer resistance as compared to MoO 3 @C and MoO 3 nanowires electrodes. Two probe electrical conductivity ( I–V ) measurements confirm the enhanced conductivity of rGO/MoO 3 @C nanocomposite relative to MoO 3 @C and bare MoO 3 nanowires. The electrical and electrochemical measurements indicate that the rGO/MoO 3 @C nanocomposite is promising candidate for energy storage applications.

A series of ferrite nanostructures Ni1+xZrxFe2–2xO4 (0.00≤x≤0.15) were prepared via wet chemical route (chemical co-precipitation route). In this study, the iron (Fe3+) metal ions were substituted with zirconium (Zr4+) and nickel (Ni2+) metal ions. Zirconium is a good dielectric metal; however, the main purpose of nickel was to maintain the magnetic parameters of NiFe2O4 that could be reduced by replacement of iron ions with zirconium ions. The prepared nanoparticles were characterized by X-ray diffraction, scanning electron microscopy (SEM), vibrating sample magnetometer (VSM) and impedance analyzer. XRD data confirmed the single phase cubic structure of all compositions of Ni1+xZrxFe2–2xO4 nanoparticles. The crystallite size calculated from XRD data using Scherrer's formula was found in the range 35–84 nm. SEM analysis provided the morphological details of the grains, grain size and level of aggregation of grains. The average grain size estimated from typical SEM image was 45–95 nm. Magnetic properties such as saturation magnetization (Ms), retentivity (Mr) and coercivity (Hc) were studied by M-H loops. All the M-H loops were recorded by varying the applied magnetic field in the range −10 kOe to 10 kOe at room temperature. Coercivity and saturation magnetization values became considerably large with the zirconium doping in nickel ferrites. Dielectric properties were studied in the alternating current frequency range of 1×106 Hz to 3×109 Hz. Dielectric constant and dielectric loss varied inversely with the applied alternating current frequency. Both magnetic and dielectric studies of Ni1+xZrxFe2–2xO4 nanoparticles exhibited the potential applications of these nanoparticles in high frequency devices fabrication.

In this study the Mn 1–2x Zr x Fe 2−y Ni y O 4 nanoparticles fabricated by co-precipitation technique were investigated. Thermo-gravimetric analysis (TGA) exhibited the annealing temperature of the nanoparticles ~990 °C. Cubic spinel structure of Mn 1–2x Zr x Fe 2−y Ni y O 4 nanoparticles was confirmed by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) analysis. Crystallite size was calculated by XRD data and found in the range of 32–58 nm. Photocatalytic activity of Mn 0.92 Zr 0.04 Fe 1.88 Ni 0.12 O 4 /graphene nanocomposites was tested by degrading methylene blue (MB) under visible light irradiation. The MB was almost completely degraded in the presence of Mn 0.92 Zr 0.04 Fe 1.88 Ni 0.12 O 4 -graphene nanocomposites under visible light irradiation. Dielectric parameters were also investigated in the frequency range 1×10 6 –3×10 9 Hz. An overall decrease in the values of dielectric constant, dielectric loss and tangent loss was observed on account of the substitution of Zr and Ni with Mn and Fe cations.

Magnetically separable rGO/MgFe2O4 nanocomposites having favorable photocatalytic activity were prepared by one step hydrothermal method. X-ray diffraction, Fourier transform infrared spectroscopy and raman analysis confirmed the spinel structure of magnesium ferrite nanoparticles. The UV–visible measurements indicated that the rGO/MgFe2O4 photocatalyst exhibits the strong visible absorption. Two probe electrical conductivity (I-V) measurements exhibited the higher conductivity of rGO/MgFe2O4 nanocomposite relative to MgFe2O4 nanoparticles. The magnetic measurements showed that the rGO/MgFe2O4 nanocomposite could be collected from water when an external magnetic field is applied. The photocatalytic studies were carried out by taking methylene blue as model organic compound under visible light irradiation. The photo-electrochemical (PEC) water splitting properties of the rGO/MgFe2O4 nanocomposite exhibited higher PEC performance compared to MgFe2O4 nanoparticles owing to the suppression of charge recombination. The results showed that nanocomposite can be used as photocatalysts for degradation of organic compounds in the polluted water.

Rare-earth (RE=La 3+ , Nd 3+ , Gd 3+ , Tb 3+ , Dy 3+ ) doped Ba 2 NiCoRE x Fe 28− x O 46 ( x =0.25) hexagonal ferrites were synthesized for the first time via micro-emulsion route, which is a fast chemistry route for obtaining nano-sized ferrite powders. These nanomaterials were investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), as well as vibrating sample magnetometer (VSM). The XRD analysis exhibited that all the samples crystallized into single X-type hexagonal phase. The crystalline size calculated by Scherrer's formula was found in the range 7–19 nm. The variations in lattice parameters elucidated the incorporation of rare-earth cations in these nanomaterials. FTIR absorption spectra of these X-type ferrites were investigated in the wave number range 500–2400 cm −1. Each spectrum exhibited absorption bands in the low wave number range, thereby confirming the X-type hexagonal structure. The enhancement in the coercivity was observed with the doping of rare-earth cations. The saturation magnetization was lowered owing to the redistribution of rare-earth cations on the octahedral site (3b VI ). The higher values of coercivity (664–926 Oe) of these nanomaterials suggest their use in longitudinal recording media.

BiFe1–2xZrxMgxO3 (x = 0.00, 0.05, 0.1, 0.15, 0.2 and 0.25) nano-sized multiferroics were synthesized by micro emulsion technique. The structure analysis, thermogravimetric analysis (TGA), fourier transform infrared spectroscopy (FTIR), magnetic measurements and dielectric properties were studied for prepared samples. Differential scanning calorimetry (DSC) and differential thermogravimetric analysis (DTA) confirm multiferroic characteristics of the samples. DTA curve indicates the presence of ferroelectric transition temperature at 806.79 °C. XRD results indicated that crystallite size is found in the range of (22.5–18.00) nm and other parameters like bulk density, X-ray density and porosity were also measured from the XRD data and were greatly influenced by increasing the dopants concentration. FTIR spectra revealed that the characteristics bonds of BiFeO3 are appreciably influenced by Zr–Mg contents. Magnetic analysis reveals that saturation magnetization (Ms) and remanent (Mr) increase with Zr–Mg doping because magnetic moment of Zr4+ is zero and doping of Zr4+ at Fe3+ site increase align spin but Mg2+ doping in BiFeO3 increases saturation magnetization not too much as compared to other alkaline earth metal ions because Mg2+ contain smallest ionic radius among alkaline earth metals. Ms reaches maximum value of 0.979 emu/g for composition x = 0.25. Multiferroics BiFe1–2xZrxMgxO3 are useful for ferroelectric random access memories (FeRAM) where data can be written electrically and read magnetically. It is found that all dielectric parameters strongly dependent on Zr–Mg contents. At higher concentrations, complicated dielectric behavior is observed. Dielectric results exhibited that dielectric parameters decrease with increase in frequency in the range of 1 MHz–3 GHz suggest that these multiferroics are useful for high resonant circuits.

We reveal that nano-scale carbon layer deposited by hydrothermal process on molybdenum oxide (MoO 3 ) nanowires surface significantly improve the light absorption range. Furthermore, the graphene-carbon coated MoO 3 nanocopmosite (rGO/C-MoO 3 nanocomposite) exhibits excellent chemical stability and enhanced photocatalytic activity for methylene blue in aqueous solution under visible light irradiation compared to the bare MoO 3 nanowires and carbon coated MoO 3 nanowires (C-MoO 3 nanowires). The enhanced photocatalytic activity of rGO/C-MoO 3 nanocomposite could be attributed to the extended light absorption range, better adsorptivity of dye molecules and efficient separation of photogenerated electrons and holes. Overall, this work provides new insights that the as synthesized rGO/C-MoO 3 nanocomposite can be efficiently used as high performance photocatalysts to improve the environmental protection issues under visible light irradiation.

Terbium (Tb) doped X-type hexagonal nano-ferrites Sr 2 NiCoTb x Fe 28− x O 46 ( x =0.00, 0.05, 0.1, 0.15, 0.2) were synthesized via micro-emulsion route. Single phase X-type hexagonal structure was confirmed by X-ray diffraction (XRD) analysis. The crystallite size of the samples was found in the range of 15–25 nm. The bulk density and X-ray density were enhanced while porosity was reduced with the increased Tb 3+ contents. The development of hexagonal phase was investigated by thermogravimetric analysis. The fourier-transform infrared (FTIR) spectra revealed the formation of spectral bands (metal-oxygen stretching vibration) which confirmed the hexagonal ferrites. The dielectric constant has high value at low frequency and decreased with increased frequency. The dielectric loss is appreciably decreased by the Tb 3+ incorporation and resonance phenomenon occurred beyond 1.7×10 9 Hz. The saturation magnetization (76–54 emu/g) and remanance (27–21 emu/g) decreased while coercivity increased (610–747 Oe) by Tb 3+ -incorporation in Sr 2 NiCoTb x Fe 28− x O 46 ferrite. The values of squareness ratio (0.35–0.39) indicated that Tb-doped samples are single domain while un-doped material is multi domains. These synthesized nano-sized hexagonal ferrites have potential applications in high frequency and recording media devices.

A series of nanostructured ferrites having chemical composition Mg0.7Co0.3YbxFe2−xO4 (x=0.0–0.08) was prepared by the chemical co-precipitation route. The synthesized samples were characterized by X-ray diffraction (XRD), Thermo-gravimetric analysis (TGA), differential thermal analysis (DTA), vibrating sample magnetometer (VSM) and impedance analyzer. The analysis of XRD patterns confirmed the spinel structure and the crystallite size calculated by Scherer's formula was found in the range of 18–43 nm. The crystallite size was small enough to obtain considerable signal to noise ratio in the recording media. The lattice constant was increased from 8.362 Ǻ to 8.383 Ǻ as the Yb contents were increased in the magnesium-cobalt ferrites. The TGA and DTA were carried out for prepared sample to investigate the thermal decomposition process. Magnetization results obtained from VSM measurements elucidate that the substitution of rare earth ytterbium decreased the saturation magnetization and retentivity. The dielectric properties of the samples were studied at room temperature in the frequency range of 1 MHz to 3 GHz and the samples exhibited the dispersion in high frequency region. The dielectric constant (e) and dielectric loss (tan δ) were decreased with the increased frequency and ytterbium doping. The dielectric parameters were explained on the basis of space charge distribution. The dielectric and magnetic parameters suggested that these nano-materials are potential candidates for switching and recording media applications.

Copper nanoparticles were prepared by chemical reduction of copper nitrate by sodium borohydride as a reducing agent in de-ionized water/acetonitrile mixture. The prepared nanoparticles were incorporated in poly(vinyl alcohol) (PVA) by physical dispersion method to obtain PVA/copper nanocomposites. Various compositions of nanocomposites were obtained by changing the w/w ratio of nanoparticles with the polymeric material. The prepared nanocomposites cast into films of uniform thickness. The composite films were subjected to the electrical, mechanical and surface morphology characterization. AC Impedance was figured out by AC Impedance analyser. The results illustrated that copper nanoparticles impart electrical conductivity in poly(vinyl alcohol). Moreover, electrical conductivity of the composites exhibited an increase with an increase of w/w% of the copper nanoparticles in poly(vinyl alcohol). Tensile properties were studied in terms of tensile strength, elongation at break and Young’s modulus. Elongation at break and Young’s modulus values demonstrated an increase while tensile strength displayed a decrease at higher concentration of the copper nanoparticles in the composites. AFM results unfolded the surface morphology of the composites illustrating a smooth surface with evenly distributed copper nanoparticles in the polymer matrix. The dimensions of the uneven surface is attributed to the copper nanoparticles were estimated to be of a range less than 100 nm. The prepared nanocomposites are suggested as potential candidates in charge storing devices.

Novel Ni 0.6 Zn 0.4 Y 2 x Fe 2−2 x O 4 soft spinel ferrites were prepared via double sintering ceramic route. The influence of Y 3+ cations on structural, morphological, electrical and dielectric properties was investigated. X-ray diffraction (XRD) confirmed the formation of single phase spinel structure for 0≤ x ≤0.06 and thereafter a small peak of orthorhombic phase (FeYO 3 ) appeared for x >0.06. The incorporation of yttrium altered the lattice constant. The variation in lattice constant with respect to the Y 3+ contents was non-linear. The variation of lattice constant may be attributed to larger ionic radius of Y 3+ as compare to Fe 3+ cations and solubility limit of substituted cations. Fourier transform infrared (FTIR) spectra showed two strong absorption bands around 600 cm −1 and 400 cm −1 which confirmed the spinel structure. The dc electrical resistivity was found to increase from 5.67×10 5 to 8.48×10 8 Ω cm with the increased Y 3+ contents. The dielectric constant and dielectric loss tangent were significantly impeded by increasing the yttrium contents. The optimized electrical resistivity and reduced dielectric parameters suggest the possible use of these ferrites in the fabrication of microwave devices.

A wet chemical route was utilized to synthesize iron oxide nanoparticles for the photocatalytic degradation of the Methylene Blue (MB) dye. The former (γ-Fe2O3) was also used to fabricate composite with graphene oxide (GO). X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM) were used to confirm the prepared compounds and their composites with GO. XRD confirmed the crystalline structure with the corresponding patterns and other physical parameters. The wider peaks showed the less crystallite size of prepared samples. SEM images showed that the nanoparticles have relatively spherical morphology. The size estimated from the SEM images was in the range of 70–100 nm. The surface properties such as specific surface area and pore size were also determined by N2 adsorption-desorption measurements. The specific surface areas determined from BET analysis were 50 m2/g and 73 m2/g for iron oxide nanoparticles and their composite with GO, respectively. High surface area provided more attachment sites for the adsorption of methylene blue (MB) molecules with γ-Fe2O3 @ GO. Further GO suppressed the aggregation of iron oxide nanoparticles. UV spectroscopic analysis led towards band gap energy value which motivated the optical properties of the nanoparticles. As the nanodomain of particles was lowered, the band gap values increased. Therefore the efficacy of γ-Fe2O3 @ GO nanomaterials was improved. The photodegradation of MB by γ-Fe2O3 @ GO was observed up to 90.6% compared to γ-Fe2O3 and Fe3O4 nanoparticles. Easy electronic conduction from valence band to conduction band and suppression of charge carrier recombination at photocatalyst surface could also increase the photocatalytic activity of photocatalyst.

Well-defined mesoporous Ag-doped Co3O4 nanosheets (NSs) has been synthesized directly on Ni-foam (NF) via a facile hydrothermal and post-annealing approach. The tune bandgap and improved electrical conductivity of the Ag-doped Co3O4 sample are confirmed by UV–visible spectroscopy and two probe current-voltage (I–V) measurements. The Ag-doped Co3O4 sample exhibits a higher surface area (176 m2g-1) than that of the pristine Co3O4 sample (108 m2g-1). The Ag-doped Co3O4/NF based electrode shows superior specific capacitance of 1425 Fg-1 at 1 Ag-1 and outstanding rate capability as it retains 92.84% of its initial specific capacitance (at 1 Ag-1) even at higher the current density of 10 Ag-1. Moreover, the specific capacitance of the material increases up to 104.7% of its initial capacitance for the first 2000 cycles, and then it gradually decreases to 96.4% after 5000 cycles. In fact, the superior electrochemical properties of the mesoporous Ag-doped Co3O4 nanosheets are attributed to its tuned bandgap, improved specific surface area, mesoporous architecture, and binder-free design. The electrochemical results revealed that the mesoporous Ag-doped Co3O4 NSs can be used as potential electrode material in the high-performance electrochemical capacitor.

Novel graphene supported ternary nanocomposites (WO3-ZnO@rGO) were prepared via simple ultrasound assisted fabrication of WO3-ZnO binary nanostructures over 2D rGO nanosheets. Structural, morphological and elemental characterization of as-synthesized samples were carried out through X-ray Diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Field emission scanning electron microscopy (FE-SEM) and Energy dispersive X-ray spectroscopy (EDX). Optical band gap analysis under UV–vis spectroscopy (UV–vis) revealed a decrement in the band gap energy value of WO3-ZnO@rGO ternary nanocomposites. Current-voltage (I–V) measurements evidenced the ohmic response of rGO supported WO3-ZnO nanocomposites as compared to bare samples. To evaluate the photocatalytic efficiency of WO3-ZnO@rGO nanocomposites in comparison to bare nanostructures, wastewater organic pollutant methylene blue (MB) dye was chosen as benchmark reaction. Results suggested that impregnation of WO3-ZnO over rGO sheets significantly improved the photocatalytic efficiency of WO3-ZnO@rGO with 94 % dye removal within 90 min under visible light irradiation. The enhanced photocatalytic efficiency is ascribed to synergistic effects originating at WO3-ZnO@rGO interfaces subsidizing high quantum yield and effective separation and transfer of photo induced electron-hole pairs. Moreover, WO3-ZnO@rGO also retained its remarkable dye degradation efficiency even after four recycling tests.

MnO2 nanomaterials were synthesized using a simple wet redox method. Crystal structure of as prepared pure and Al doped MnO2 nanomaterials was investigated using X-ray diffraction (XRD) technique. Crystal structure was further confirmed by FTIR analysis. Morphology of pure MnO2, Al doped MnO2, MnO2/CNT hybrid structure and Al doped MnO2/CNT hybrid structure was studied using scanning electron microscopy (SEM). Energy dispersive X-ray spectroscopy confirmed the presence of all the constituent atoms in the crystal structure of all the samples. Bandgap value was found to decrease with the modification (doping and hybrid structure). Photocatalytic efficiency of all the MnO2 samples was studied using the photodegradation of methylene blue (MB) under the visible light (solar radiation). Effect of different intermediates on the photodegradation efficiency was studied using different scavengers.

An efficient electrochemical sensor based on reduced graphene oxide decorated with alanine and polyaniline was developed for the real-time analysis of heavy metal ions (Cd2+, Pb2+, and Cu2+). The morphological and structural analysis of as-synthesized nanocomposite was conducted via X-ray diff ;raction approach (XRD), UV/Visible analysis, Fourier transform-infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The electrochemical characteristics of the electrode modifiers were examined through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) using standard potassium ferrocyanide as a redox probe. Various sensitivity influencing factors such as chemical and electrochemical parameters including pH effect, deposition potential, deposition time and effect of supporting medium were also determined to enhance the effectiveness of the designed sensor. The interference ability of the designed sensor was also studied in the presence of various inorganic and organic species. Proposed methodology endorsed the sensitive and robust analysis of the toxic metal ions with a remarkable low detection limit of 0.03 nM, 0.045 nM and 0.063 nM for Cd2+, Pb2+, and Cu2+ ions, in the linear range of 100 nM–0.08 nM respectively. The proposed method exhibited high sensitivity and selectivity towards Cd2+, Pb2+, and Cu2+ ions detection which can be attributed to the strong binding affinity of rGO/Ala/PANI nanocomposite with these target metal ions. These results suggested that this methodology can be applied for sensitive detection of other organic and inorganic pollutants in water samples.

The facile single-step hydrothermal route was adopted to prepare Mo doped ZnS (Mo: ZnS) with honeycomb-like structure and deposited directly on the nickel foam (NF). Benefiting from the higher surface area with hierarchical pore sized distribution, binder-free electrode/substrate contact, and intrinsically improve electronic conductivity resulting from Mo doping, Mo: ZnS@NF electrode exhibited 2208 Fg−1 gravimetric capacitance (Cg) at the current density 1 Ag−1. The honeycomb-like the architecture of Mo: ZnS provides a larger surface area with more active sites and shortens the path for the charge diffusion. Moreover, asymmetric supercapacitors (Mo: ZnS@NF//AC@NF) display74.87 Fg−1 Cg at 2 Ag−1 current density and long term stability with 91.3 % capacitance retention after 5000 CCD (cyclic charge/discharge) tests. The high energy density of 26.5 Wh kg−1 is achieved at a power density of 1303 W kg−1. The obtained results demonstrate the superior capacitive activity of Mo: ZnS/NF electrode for advanced energy storage devices.

In the current investigation, graphene (rGO)-supported cerium substituted nickel ferrite (NiCeyFe2-yO4 y = 0.05) photocatalyst was prepared via two-step wet chemical approach. The resulting NiCeyFe2-yO4/rGO nanocomposite exhibited excellent photocatalytic performance and stability. Moreover, the photocatalytic activity of NiCeyFe2-yO4/rGO nanocomposite was also investigated comparatively with NiCeyFe2-yO4 nanoparticles. As compared to the NiCeyFe2-yO4 nanoparticles, NiCeyFe2-yO4/rGO nanocomposite showed superior photocatalytic efficiency and recycling stability for MB degradation, which is two times that of bare NiCeyFe2-yO4 nanoparticles. After visible light irradiation for 70 min, 94.67 % of MB dye was removed by NiCeyFe2-yO4/rGO nanocomposite whereas only 50 % of MB dye was removed by NiCeyFe2-yO4 nanoparticles. The increase in photocatalytic performance is mainly ascribed to formation of NiCeyFe2-yO4/rGO heterojunction which not only assist in separation of photo-induced charge carriers, but also sustain a strong redox ability. Moreover, the photo-corrosion of NiCe0.05Fe1.95O4 nanoparticles is inhibited through transfer of photo-induced electrons of NiCe0.05Fe1.95O4 nanoparticles to rGO. A possible photo-degradation mechanism based on reactive species trapping experiments has been proposed. The effect of various factors like pH, temperature and catalyst dosage has also been explored. Facile synthesis method, excellent photocatalytic performance for organic pollutants and superior reusability suggest that NiCeyFe2-yO4/rGO photocatalyst possesses high potential for large-scale pollutant treatment.

In this article, we reported the two-step wet chemical co-precipitation and ultra-sonication route to synthesize the Ce0.95Fe0.05O2/NiO/rGO (CFN-rGO) ternary composite photocatalyst. The photocatalytic activity of the ternary composite was evaluated by the photodegradation of Rhodamine B (RhB) dye under visible light irradiation. The CFN-rGO photocatalyst exhibited an excellent photocatalytic performance with 97% removal of RhB within 130 min of irradiation time, as compared to the bare Ce0.95Fe0.05O2/NiO (CFN) binary composite photocatalyst. The value of rate constant for RhB degradation was nine times higher with CFN-rGO when compared to the pure CFN catalyst. The superior photocatalytic activity of CFN-rGO is attributed to the presence of reduced graphene oxide (rGO), that effectively suppress the fast recombination of photo-generated electron-hole pairs which in turn find enough time to produce more reactive species for RhB dye degradation. The main photo-active species involved in photodegradation of RhB dye molecules were the hydroxyl radicals ( H O • ). Finally, the recyclability tests performed over CFN-rGO suggested good stability of the photocatalyst even after five cycles and hence, endorsing its potential as a candidate for practical photocatalytic applications.

Transition metal spinel type mixed oxides (FeCo2O4, MnCo2O4 and ZnCo2O4) nano-catalysts have been synthesized via co-precipitation route. The samples were characterized using XRD and FE-SEM techniques to determine structure and morphologies respectively. Furthermore, FTIR and BET analysis were carried out in order to confirm the structure and calculate surface areas of the samples. The photocatalytic potency of synthesized nano-catalysts have been examined for aqueous solution of methylene blue under visible light. It is found that photocatalytic activity of simple transition metal oxides was enhanced by making their binary/ternary metal oxides. FeCo2O4 exhibited highest photocatalytic efficiency among the prepared spinel structures while MnCo2O4 possess lowest efficiency. The photocatalytic behavior of mixed transition metal oxides can be accredited to its spinel structure, small particle size and large surface area. XRD and BET results revealed the small crystallite and particle size of spinel mixed oxides. The small crystallite size of spinel mixed oxides nano-structures contributes to increased photocatalytic activity by increasing the surface area of photocatalyst, decreasing the chance of reunion of charge carriers. It is observed that these binary oxide nano-structures have potential applications in heterogeneous photo decay of environmental contaminants and can act as propitious materials for resolving environmental issues and establishing green environment.

In this work, Fe-doped In2O3 nanostructures have been prepared using a simple chemical route. Various physio-chemical properties have been investigated. XRD results show that Fe dopant induces no impurity phase in cubic In2O3. For optical properties, Fe dopant induced blue-shift appears in absorption spectrum of In2O3. A comparison of photocatalytic activity of neat In2O3 and Fe-doped In2O3 nanoparticles has been obtained. An enhancement of UV light triggered photocatalytic activity to photodegrade methylene blue, RhB and methyl orange upto 83%, 95.36% and 93.77% respectively has been achieved. The existence of oxygen vacancies in Fe doped In2O3 and optimized bandgap makes Fe doped In2O3 a potential photocatalyst.

Polycrystalline oxide YxMnFe2−xO4 was prepared via low-cost micro emulsion method. As concentration of yttrium ions increased, their electrical and magnetic properties were changed. Effect of secondary phase YFeO3 on the electrical and magnetic properties of the material were also studied and discussed in detail. As concentration of impurity ions increased, variation in resistivity was observed. This variation also affected the magnetic behavior of the prepared Mn-based spinel ferrites. Various parameters such as the saturation magnetization (Ms), retentivety (Mr), coercivity (Hc), anisotropic constant (k1), magnetic moments (μB) have been calculated from recorded M-H loops of all unsubstituted and substituted MnFe2O4 nanoparticles. Ms and Mr values found in the range 27–50 emu/g and 1.8–7.6 emu/g respectively.

Multi metal based photocatalyst (CdO-MgO-Fe2O3) was synthesized via wet chemical approach i.e. co-precipitation method. The single transition metal oxides like CdO, MgO and Fe2O3 were also prepared for comparative studies. Structural elucidation of all prepared powder catalysts (CdO, MgO, Fe2O3 and CdO-MgO-Fe2O3) was conducted by X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). XRD showed the presence of the MgO (cubic) – Fe2O3 (rhombohedral)– CdO (cubic) phase with an average crystallite size of MgO (9 nm), Fe2O3 (12 nm), CdO (23 nm). FTIR proved the existence of Mg–O, Fe2-O3 and Cd-O by distinctive vibrational bands at 772 cm−1, 581 cm−1 and 480 cm−1 respectively. UV–vis spectral studies showed that the bandgap for CdO-MgO-Fe2O3 nanocomposite was 1.76 eV which made it an efficient photocatalyst for use both in the UV and visible regions. Two probe I–V measurements confirmed the pure semiconducting behavior and possible formation of heterojunction in the CdO-MgO-Fe2O3 nanocomposite. The photocatalytic performance of the CdO-MgO-Fe2O3 nanocomposite with equal metal ion concentration of Mg, Fe and Cd at different pH values was explored by visible light illumination on methylene blue (MB) dye as a standard organic pollutant. The CdO-MgO-Fe2O3 nanocomposite with metal ion ratio 1:1:1 in an alkaline medium showed the maximum photocatalytic performance. The rate constant (kMB) value for the degradation of MB was ∼ 0.0820 min−1. The photocatalytic activity has been improved due to the effective decrease in the recombination rate of charge carriers. The possible mechanism for improvement of the photocatalytic performance using visible light illumination has also been suggested and discussed.

Co-precipitation method was used to synthesize the nanoparticles of cobalt substituted zinc–magnesium ferrites having formula “Mg 0.6−0.5 x Zn 0.4−0.5 x Co x Fe 2 O 4 ” where 0.00 ≤ x ≤ 0.25 . Fabricated samples were annealed at 750 °C for 6 h. The cubic spinel structure of Mg 0.6−0.5 x Zn 0.4−0.5 x Co x Fe 2 O 4 nanocrystals was confirmed by Fourier transformed infra-red (FTIR) and X-ray diffraction (XRD). Lattice parameter, crystalline size, cell volume, X-ray density, bulk density and porosity were also determined using XRD data. Lattice parameter exhibits overall decreasing trend (0.824–0.817 nm) with cobalt content; it is due to the substitution of cobalt (having smaller ionic radii) with magnesium and zinc ions. Cation distribution among A and B sites were studied by FTIR spectrum. Vibrating sample magnetometery (VSM) was used to investigate magnetic properties of as prepared nanoparticles. Coercivity exhibits the inverse relation to crystalline size. Lowest value of coercivity (47.722 Oe) was obtained for the sample having x =0.15. Dielectric constant, dielectric loss and dielectric tan loss were inversely related with the frequency.

In this paper, we have grown an 80 nm thick Gd 2 O 3 thin film by electron beam evaporation on glass substrate and fabricated different metal (Al, Cu, Cr and Au) electrodes on grown sample under same condition. To investigate the charge transport mechanism in these metal-semiconductor systems, the electrical conductivities and current–voltage (I–V) measurements have been measured over temperature range of 250–400 K. We have found that Mott variable range hopping (VRH) is responsible for conduction behavior in all systems for entire temperature range. A strong correlation between transport properties and metal work function has been observed. A space charge model successfully explained the decreasing trend of conductivity with increasing the metal work function. The conductivity decreased from 2.9 × 10 −5 to 1.8 × 10 −11 S/cm as the metal work function increased from 4 to 5.1 eV for Al to Au metals respectively. The ideality factor also increased from 1.67 to 2.2 with metal work function from Al to Au metal. The observed result can be explained as; high work function metal forms higher depletion layer as compared to metal having low work function, which compensate the empty sites available for hopping and consequently decreased the hopping conductivity.

Dy 3+ and Fe 3+ co-doped LaCoO 3 perovskite nanoparticles were prepared by chemical co-precipitation route. Structural elucidation was carried out by thermo gravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared (FTIR) spectroscopy. The data of all these characterization techniques confirmed the orthorhombic phase with particles size in the range of 20–60 nm. The magnetic parameters, DC-resistivity and dielectric properties were measured for La 1− x Dy x Co 1− y Fe y O 3 nanoparticles. The purpose of all these application studies was to evaluate the prepared materials for practical applications. The substitution of Dy 3+ and Fe 3+ with La 3+ and Co 3+ respectively greatly influenced the magnetic, DC-resistivity and dielectric parameters.

Co and Ni substituted znic ferrite nanoparticles (Zn1−xCo0.5xNi0.5xFe2O4) (0.00≤x≥0.75) were synthesized by co-precipitation method. X-ray diffraction and Fourier transform infrared spectroscopy confirmed the single phase spinel structure. The lattice constant decreased with the increased Co and Ni contents. The bulk density was found less as compared to the X-ray density and this difference was explained in terms of porosity. The crystallite size was calculated by Scherrer's formula and found in the range 20–50 nm. Two prominent stretching bands were observed in FTIR spectra around 400–600 cm−1. These two bands confirmed the spinel structure of the prepared nanoparticles. The saturation magnetization was found to increase upto x=0.60 from 1.31 emu/g to 81.2 emu/g then it decreased for x=0.75 to the value of 75.1 emu/g. The coercivity and retentivity were found in the range 35.36–226.125 Oe and 0.0135–19.8 emu/g, respectively. Dielectric parameters were decreased with the increased Ni–Co contents. About nine fold increase in the DC-electrical resistivity was obtained for the Zn0.25Co0.375Ni0.375Fe2O4 (2.8979×1010 Ω cm) as compared to the ZnFe2O4 (0.2974×1010 Ω cm) nanoparticles.

Pb 1−1.5x Nd x ZrO 3 nanocrystalline powder (x = 0, 0.01, 0.02, 0.03, 0.04, 0.05) have been synthesized by co-precipitation technique. The prepared samples were annealed at temperature 700 °C for 3 h. The structural, dielectric and DC-electrical behavior of the Pb 1−1.5x Nd x ZrO 3 nanoparticles was evaluated using the X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, dielectric analysis and current–voltage (I–V) characteristics. XRD analysis confirmed the formation of orthorhombic perovskite structure and the crystallite size estimated was 47.80–102.62 nm. The crystallite size and lattice parameters showed a nonlinear behavior. The FTIR spectra were recorded in the range 500–4000 cm −1 that explained the intrinsic cation vibrations of the characteristic orthorhombic perovskite structure. The dielectric parameters were studied in the frequency range of 1 × 10 6 Hz to 3 × 10 9 Hz. In the dielectric parameters, a damping effect was observed by the substitutions of Pb with Nd ions in the higher frequency region. The dominating effect of doping on dielectric properties suggests that these nanomaterials are useful in the fabrication of high frequency and memory devices. DC-electrical measurements showed the increased resistivity as the Nd 3+ content was increased. The minimum resistivity was observed for 2.3547 × 10 9 Ω-cm for PbZrO 3 nanoparticles, while Pb 0.925 Nd 0.05 ZrO 3 nanoparticles showed the maximum resistivity 1.2283 × 10 10 Ω-cm. This fivefold increase in DC-resistivity strongly supports the fabrication of high frequency devices.

Soft ferrites are technologically advanced smart materials and their properties can be tailored by controlling the chemical composition and judicial choice of the metal elements. In this article we discussed the effect of rare earth neodymium (Nd3+) on various properties of LiNi0.5NdxFe2−xO4 spinel ferrites. These ferrites have been synthesized by facile micro-emulsion route and characterized by X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), a.c. electrical conductivity and thermal analysis. The influence of Nd3+ doping on structural and electrical parameters has been investigated. XRD analysis revealed the formation of single cubic spinel structure for x≤0.07. Few traces of secondary phase (NdFeO3) were found for x≥0.105. The secondary phase induced owing to the solubility limit of Nd3+ cations in these ferrites. The lattice parameter (a) and crystallite size (D) both exhibit non-linear relation. The values of “a” and “D” were found in the range 8.322–8.329 A and 25–32 nm respectively. These variations were attributed to the larger ionic radius of Nd3+ cations as compared to the host cations and lattice strain produced in these ferrites. The dielectric parameters were studied in the range 1 MHz to 3 GHz and these parameters were damped by Nd3+ incorporation and also by increasing the frequency. The reduced dielectric parameters observed in wide frequency range proposed that these nanocrystalline ferrites are potential candidates for fabricating the devices which are required to operate at GHz frequencies.

Nano-crystalline Li 0.5 Co 0.5 Nd x Fe 2− x O 4 ( x = 0.0, 0.035, 0.070, 0.105, 0.140, 0.175) ferrites have been synthesized via micro-emulsion technique. Thermal analysis, fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), magnetometer analysis and a.c. electrical studies are employed to observe the impact of Nd 3+ doping in Li 0.5 Co 0.5 Fe 2 O 4 on crystallite size, spectral bands, dielectric and magnetic parameters. Thermal analysis depicts the weight loss with various temperatures and it illustrates that there is no further weight loss above 950 °C. XRD analysis establishes the formation of single phase cubic spinel structure. Although for x = 0.0 and thereafter for x ⩾ 0.035 a peak of second phase (NdFeO 3 ) occurs. The XRD data analysis revealed that the Nd substituted Li 0.5 Co 0.5 Fe 2 O 4 ferrites revealed crystallite size 52.02–106 nm ranges. The lattice parameter and crystallite size show a nonlinear behavior. The FTIR data between 400 and 1000 cm −1 defined the intrinsic cation vibrations of the characteristic spinel structure. The dielectric parameters are investigated in the range of 1 MHz–3 GHz frequency. A damping effect in the dielectric parameters is observed by Nd 3+ incorporation and also by increasing the frequency. Magnetic measurements at room temperature exhibit an appreciable increase in the saturation magnetization and coercivity with the substitution of Nd 3+ cations. Coercivity is in range of soft ferrite. The dominating effects of doping on dielectric properties propose that these nano-ferrites are useful in the fabrication of high frequency devices, whereas increase in magnetization and coercivity propose the use for high density recoding media.

La 1− x Tb x FeO 3 nanoparticles (where x =0.00, 0.02, 0.04, 0.06, 0.08) prepared via micro emulsion method were characterized by Thermogravimetric analysis (TGA), X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Fourier transform infra-red spectroscopy (FTIR). According to TGA analysis, the phase formation temperature identified was about 989 °C. Both XRD and FTIR confirmed the orthorhombic structure of La 1− x Tb x FeO 3 nanoparticles. The crystallite size estimated by XRD was in the range 40–75 nm. The cell volume measured by XRD was found to decrease upon substitution. The general trend deviated for x =0.08. The SEM analysis of nanoparticles estimated the particle size in the range 50–95 nm. After characterization the nanoparticles were subjected to the dielectric behavior evaluation in the frequency range 1×10 6 Hz to 3.0×10 9 Hz. Dielectric parameters were decreased by substitution of La 3+ with rare earth Tb 3+ ions. The dielectric studies showed the possible utilization of these nanomaterials in high frequency devices.

Gd 1− x Bi x Fe 1− y Zr y O 3 nanoparticles were synthesized via micro-emulsion route with different molar concentrations of Bi +3 ( x ) and Zr +4 ( y ). The values of x and y were kept in the range 0.00, 0.15, 0.30, 0.45 and 0.60. The characterizations were done by the thermo-gravimetric analysis (TGA), X-ray Diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The average particle size was ~50 nm. The effect of Bi 3+ and Zr 4+ contents on electrical, dielectric and magnetic parameters were studied. The DC resistivity measurements showed at certain Bi 3+ and Zr 4+ contents, more than two fold increase in electrical resistivity from 68×10 8 Ω cm to 150×10 8 Ω cm. The magnetic measurements showed the paramagnetic nature of Gd 1− x Bi x Fe 1− y Zr y O 3 nanoparticles. The electrical and magnetic properties of these nanoparticles suggested that these materials are potential candidates for the fabrication of telecommunication and switching devices.