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In this study, the precipitation and sonication methods were used to fabricate WO3–NiO/rGO nanohybrid. The structural, spectral and optical characteristics of the as-synthesized samples were confirmed using X-ray diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), and UV–Visible spectroscopy. In comparison to pure WO3, NiO and WO3–NiO, WO3–NiO/rGO nanohybrid demonstrated increased photocatalytic degradation activity for rhodamine B and methylene blue under solar light irradiation. The percent degradation values for WO3, NiO, WO3–NiO and WO3–NiO/rGO nanohybrid for methylene blue were 64%, 81%, 86% and 95%, and for rhodamine B were 58%, 80%, 92% and 96%. The lower recombination of photo-generated holes and electrons as a result of the creation of a heterojunction between WO3 and NiO and the improved optical bandgap energy of WO3-NiO nanocomposite and its hybrid with rGO are the potential causes of this enhanced photocatalytic degradation. WO3–NiO/rGO nanohybrid demonstrated outstanding photocatalytic performance and positioned itself as a viable candidate in the catalysis industry. [ABSTRACT FROM AUTHOR]

In the current investigation, copper substituted cobalt manganese spinel oxide (CuxCo1–xMn2O4) photocatalyst was prepared via the co-precipitation method. The synthesized nanoparticles were characterized by X-ray diffraction, field emission scanning electron microscopy, and Fourier-transform infrared spectroscopy. The prepared Cu0.2Co1–0.2Mn2O4 nanoparticle exhibited excellent photocatalytic activity for degradation of typical organic-based dye Methylene blue (MB). Furthermore, the comparative study of pure CoMn2O4 and Cu-substituted CoMn2O4 nanoparticles (NPs) towards the photocatalytic performance was also conducted. As compared to the CoMn2O4 nanoparticles, the CuxCo1–xMn2O4 nanoparticles exhibited excellent photocatalytic capability for the degradation of MB dye. After 80 min of visible light irradiation, the decomposition of MB by CuxCo1–xMn2O4 nanoparticles was higher as compared to degradation MB dye in the presence of copper substituted CoMn2O4 NPs. Copper substituted cobalt manganese oxide nano-photocatalyst was also used for comparative study. The Cu0.2Co(1–0.2)Mn2O4 showed excellent (~86%) photocatalytic performance in contrast with Cu0CoMn(1–0)O4 (22%), Cu0.5Co(1–0.5)Mn2O4 (57), Cu0.1Co(1–0.1)Mn2O4 (60%), Cu0.15Co(1–0.15) Mn2O4 (73%) for the degradation of MB in visible light irradiation. The enhanced photocatalytic activity is mainly attributed to the optimized bandgap, which might have developed by the inclusion of copper ions into the CoMn2O4 spinel oxide. The copper substitution not only contributed to the inhibition of photo-induced electron–hole pairs but also assisted a great redox capability. CuxCo1–xMn2O4 photocatalyst holds great potential for massive pollutant treatment due to the superb photocatalytic performance for organic pollutants. [ABSTRACT FROM AUTHOR]

Rare earth Nd 3+ doped Mg 0.8 Ca 0.2 Fe 2 O 4 nanoparticles were prepared via chemical co-precipitation route. XRD confirmed the cubic structure of all compositions and XRD data was used to determine the lattice constant (a), cell volume (V), crystallite size (D) and porosity. Reduced graphene oxide (rGO) prepared via chemical route was utilized to obtain the Mg 0.8 Ca 0.2 Nd x Fe 2-x O 4 -rGO nanocomposite materials. SEM analysis confirmed the well dispersed Mg 0.8 Ca 0.2 Nd x Fe 2-x O 4 nanoparticles among the graphene sheets. The photocatalytic degradation rate of methylene blue was higher in the presence of nanocomposite as compared to the bare nanoparticles under visible light irradiation. The enhanced photocatalytic activity of Mg 0.8 Ca 0.2 Nd x Fe 2-x O 4 -rGO nanocomposite could be related to the decreased charge transfer resistance of composite materials investigated by electrochemical impedance spectroscopic (EIS) analysis. The value of dielectric constant and dielectric loss decreased with the increase in value of Nd 3+ from 0 to 0.12 mol. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Sol–gel approach was employed for synthesis of nickel aluminate (NiAl 2 O 4 , NA), and silver doped nickel aluminate (Ag-NiAl 2 O 4 , AgNA) nanomaterials. The ultra-sonication approach was employed to synthesize their composite with graphitic carbon nitride (Ag-NiAl 2 O 4 @g-C 3 N 4 , AgNA@gCN) for degradation of organic effluents such as methylene blue (MB), crystal violet (CV), and benzoic acid (BA) photocatalytically. The synthesized photocatalysts were characterized by various techniques like X-rays diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and UV–visible spectroscopy. XRD confirmed the formation of doped and un-doped NiAl 2 O 4. The crystallite size of as-prepared nanomaterials was found out less than 13 nm. FT-IR technique was used for functional groups detection present in synthesized photocatalysts. The surface morphology of fabricated nanomaterials was investigated via SEM. The thermal stability of prepared samples was investigated via TGA. Optical analysis was carried out by UV-Visible spectrophotometer. NA and AgNA exhibited the bandgap energy of 3.50 eV, and 2.88 eV respectively. The photocatalytic efficiency of fabricated samples was analyzed under solar light. AgNA@gCN exhibited 85.26% degradation of MB, 83.87% of CV, and 68.46% of BA under sunlight. The overall removal (%adsorption + % degradation) of MB, CV, and BA by AgNA@gCN were 99.67%, 98.54%, and 76.91% respectively. The scavenging experiment was also performed to find out the most photoactive species involve in the degradation of organic effluent photocatalytically. Hydroxyl radicals are the mainly photoactive species responsible for the photocatalytic experiment. Simple facile route was adopted to prepare Ag-NiAl 2 O 4 @g-C 3 N 4 ; a new photocatalyst, that was utilized for photodegradation of various organic effluents under solar light irradiation. [Display omitted] • Simple facile route was adopted to prepare Ag.NiAl 2 O 4 @g-C 3 N 4 , a new photocatalyst. • Photodegradation of various organic effluents by Ag-NiAl 2 O 4 @g-C 3 N 4 was studied. • Mechanistic investigation of degradation has also been discussed. [ABSTRACT FROM AUTHOR]

Environmental remediation of organic contaminants has recently received significant attention, necessitating the development of energy-efficient, cost effective, and environment-friendly catalysts. In this study, novel dual-doped La x Ni y Mn 3–(x+y) O 4 nanoparticles (NPs) and their composite with an adsorptive material (mesoporous silica) were synthesized using a low-cost, environment-friendly coprecipitation technique. The as-prepared La x Ni y Mn 3–(x+y) O 4 NPs and their composite were studied via X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), Fourier-transform infrared (FTIR) spectroscopy, and ultraviolet–visible spectroscopy. XRD analysis revealed that the La x Ni y Mn 3–(x+y) O 4 NPs possessed a crystalline structure. FESEM showed that La x Ni y Mn 3–(x+y) O 4 NPs were spherical with diameters ranging from 60 to 100 nm. The presence of metal–oxygen bonds in the La x Ni y Mn 3–(x+y) O 4 NPs was confirmed by FTIR analysis. The La x Ni y Mn 3–(x+y) O 4 NPs could degrade crystal violet (CV) dye under visible light with a percentage degradation of 82%, which increased to 92% with the addition of 0.5 mL of 6% H 2 O 2 solution. Furthermore, to increase the adsorption ability of the La x Ni y Mn 3–(x+y) O 4 NPs, a composite La x Ni y Mn 3–(x+y) O 4 /SiO 2 was synthesized. Under dark conditions, the adsorption percentage of the La x Ni y Mn 3–(x+y) O 4 NPs was 58%, whereas that of La x Ni y Mn 3–(x+y) O 4 /SiO 2 reached 73%. The adsorption process was further explored using adsorption isotherms and reaction kinetic models. The central composite rotatable design of response surface methodology was used to statistically maximize the adsorption of CV by optimizing factors such as time (40 min), pH (8.68), and composite dose (12 mg). The prominent diffraction peak in the XRD pattern and the large surface area (532 m2/g) determined via Brunauer–Emmett–Teller analysis of the composite confirmed its unique porous characteristics, illustrating its high capacity for adsorbing pollutants inside the porous network. Studies on the degradation efficiency and adsorption–photocatalysis synergy suggest the substantial potential of the synthesized composite for application in environmental remediation. [Display omitted] [ABSTRACT FROM AUTHOR]

La 1− x Cr 0.7 x Eu 0.3 x FeO 3 nanoparticles were fabricated by micro-emulsion route. The value of x was kept in the range of 0.00 to 0.04. The synthesized nanoparticles were then characterized by X-ray diffraction (XRD), Fourier transform infra-red spectroscopy (FTIR) and scanning electron microscopy (SEM). The XRD confirmed the orthorhombic phase and estimated the crystallite size in the range of 30–90 nm. The nanoparticles estimated by SEM were in the range 60–100 nm. The XRD data was further supported by FTIR spectrum. The main FTIR bands observed were: Fe–O (418 cm −1 ), Cr–O (545 cm −1 ), La–O (570 cm −1 ) and Eu–O (416 cm −1 ). After structural elucidation, the La 1− x Cr 0.7 x Eu 0.3 x FeO 3 nanoparticles were subjected to magnetic parameters and dielectric behavior evaluation. The replacement of La 3+ ions, with Cr 3+ and rare earth Eu 3+ exhibited interesting magnetic and dielectric behavior. The LaFeO 3 nanoparticles without any dopants showed the paramagnetic behavior. However as the La 3+ was substituted by Cr 3+ and Eu 3+ , the ferromagnetic behavior was observed. Similarly the dielectric parameters were reduced by the replacement of La 3+ ions with Cr 3+ and Eu 3+ metal ions. The maximum magnetic parameters were observed for La 0.6 Cr 0.28 Eu 0.12 FeO 3 (Coercivity~0.04 T, Saturation magnetization ~0.728 emug −1 and Retentivity ~0.0.6783 emug −1 ). The maximum dielectric constant (23.52 at 1.5×10 −2 GHz) was observed for LaFeO 3 nanoparticles, while the minimum value of dielectric constant (10.32 at 1.5×10 −2 GHz) was exhibited by La 0.8 Cr 0.14 Eu 0.06 FeO 3 nanoparticles. [ABSTRACT FROM AUTHOR]

The recent industrial revolution and population growth have escalated the threat to the environment. Industries themselves discharge millions of tons of different harmful solvents, chemicals, and organic/metal ions into the water system each year. For the degradation of these organic wastes, photocatalysis has been extensively studied. The most researched classes of nanoparticles used as photocatalysts in environmental remediation are metal oxide and metal ferrite nanostructures. In this context, we have fabricated magnesium ferrite (MgFe 2 O 4) nanoparticles and molybdenum trioxide (MoO 3) nanorods by coprecipitation and hydrothermal processes, respectively. Moreover, their binary composite (MgFe 2 O 4 / MoO 3) was fabricated to improve the absorption of light in the visible region. Further, its ternary composite was fabricated with CNTs (MgFe 2 O 4 /MoO 3 @CNT) to enhance photocatalytic activity by reducing the recombination rate via trapping photoinduced species. X-rays diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopic analysis were carried out for structural confirmation. From XRD data, the crystallite size and other crystallographic parameters of the fabricated samples were determined. The calculated crystallite sizes of MgFe 2 O 4 and MoO 3 were 12.74 nm and 31.36 nm, respectively. Band gap calculation and optical studies were done by UV–visible spectroscopy. The decrease in band gap value of MgFe 2 O 4 /MoO 3 leads to remarkable photocatalytic activity than bare photocatalysts. The photocatalytic performance of all photocatalysts was examined by degrading methyl orange (MO) dye, pendimethalin (PDM), and benzoic acid (BA). Comparative studies revealed that MgFe 2 O 4 /MoO 3 @CNT exhibited brilliant photocatalytic activity among the aforementioned photocatalysts. It degraded 96%, 82%, and 67% methyl orange (MO), pendimethalin (PDM), and benzoic acid (BA), respectively. This outstanding increase in photodegradation process was due to the movement of photoexcited species from the conduction band to CNTs, where it traps the photoexcited species and limits their chances of recombination. Overall, this research offers a fresh understanding of the effective utilization of the MgFe 2 O 4 /MoO 3 @CNT ternary composite as a high-performance photocatalyst to address environmental protection concerns when exposed to visible light. [Display omitted] • MgFe2O4/MoO3 binary composite and MgFe2O4/MoO3 @CNT ternary nanocomposite were synthesized. • MgFe2O4/MoO3 @CNT degraded 96% of Methylene Orange, 82% of Pendimethalin and 67% of Benzoic Acid. • Structural and morphological confirmation are analyzed by XRD, SEM, and FT-IR. [ABSTRACT FROM AUTHOR]

In this research paper, we have reported the thermal, structural, magnetic and optical properties of unsubstituted and aluminum substituted zinc ferrite nanoparticles. These substituted and unsubstituted ferrite nanoparticles were prepared by cost effective co-precipitation method. The co-precipitated unannealed nanoparticles of the typical sample were subjected to thermogravimetric analysis (TGA) to probe the annealing temperature. The X-rays diffraction (XRD) technique was used for the determination of structural parameters. XRD patterns of all compositions of Al x ZnFe 2-x O 4 nanoparticles confirmed the FCC structure of these spinel ferrite nanoparticles. Besides the main crystal structure determination, many other lattice parameters and their variations with respect to increased Al3+ contents in ZnFe 2 O 4 were also calculated from XRD data and have been discussed in detail in this article. The morphology of the synthesized materials has been studied by scanning electron microscopy (SEM) and average particles size found < 100 nm. The variation in electrical and magnetic parameters with increased Al3+ contents was studied in detail. The analysis of magnetic properties concluded that the prepared nanoparticles have good magnetic properties. At the end the optical studies of the nanoparticles proved that these spinel ferrites also have photocatalytic applications. The photocatalytic degradation of methylene blue in the presence of these samples has been studied and discussed. The ferrites particles could be separated from contaminated water simply by magnetic bars. Therefore these particles can be used and recycled easily for photocatalytic applications. The aim of work was to study the structural, electrical, magnetic and catalytic behavior of the material. [ABSTRACT FROM AUTHOR]

Nanomaterials with novel properties and broad potential applications have been widely anticipated in light of recent advances in material science. In this research, Ag-doped LaNiO 3 /MXene nanocomposite was fabricated by facile routes. Various techniques like XRD, FTIR, SEM and UV–vis absorption spectroscopy were used for the characterization. FTIR results showed different vibrational modes for Ni–O and La–O. Morphological studies were done by SEM analysis. Optical band gap was calculated using UV–vis absorption spectroscopy and the results showed a decrease in bandgap from 2.96 eV to 2.78 eV. The Orthorhombic structure of fabricated Ag–LaNiO 3 /MXene was confirmed by XRD. To evaluate the photocatalytic efficiency, bromophenol blue (BPB), methyl orange (MO), and benzoic acid (BA) were used as model wastewater contaminants. Photo-catalytic results revealed that Ag–LaNiO 3 /MXene degraded 84 %, 64 %, and 55 %, of (BPB), (MO), and (BA) respectively. Bromophenol blue highly (84 %) degraded in the whole process. For Ag–LaNiO 3 /MXene, the rate constants for BPB, MO, and BA were 0.02281 min−1, 0.01142 min−1, and 0.00789 min−1. Hence, this present work revealed that Ag–LaNiO 3 /MXene enhanced photo-catalytic efficiency at a greater rate. • Ag doped LaNiO 3 was fabricated by co-precipitation and its composite (Ag–LaNiO 3 /MXene) by an ultrasonication method. • (Ag–LaNiO 3 /MXene) is a competent photocatalyst for photocatalytic degradation of BPB, MO, and BA. • The improved phtotcatalytic activity was due to synergistic effects of as synthesized materials. [ABSTRACT FROM AUTHOR]

Nanoparticles of double heterojunction n-CuO-p-NiO-n-ZnO system and its nano-hybrids with reduced graphene oxide (rGO) were synthesized by simple and easily adoptable co-precipitation method. The prepared n-CuO-p-NiO-n-ZnO nanoparticles and their hybrids with rGO were characterized by various characterization techniques. Structural, optical and morphological characterization was done by X-rays diffraction (XRD), Fourier Transform Infrared (FTIR), UV–Visible spectroscopy etc. It was found that the developed hetero-structure is composed by p-NiO as cubic, n-CuO as monoclinic and n-ZnO as hexagonal crystal structure. Formation of heterojunction is confirmed by current-voltage (I-V) measurement. The optical bandgap energy of heterojunction was around 1.6 eV which made this system active in both UV and Visible light region. Photocatalytic degradation efficiency was examined using methylene blue and it showed prominent enhancement as compared to pure metal oxides. This excellent efficiency was attributed due to efficient charge carrier separation which leads to inhibit recombination rate at photocatalyst interface. Moreover, photocatalytic activity was increased meaningfully up to 70% by graphene based n-CuO-p-NiO-n-ZnO. This excellent increment in activity was due to large surface area offered by graphene which caused adsorption of dye molecules and helped in transfer of electrons to metal conduction band. [ABSTRACT FROM AUTHOR]

Abstract In this work erbium (Er3+) substituted cobalt zinc ferrite having general formula Co 0.70 Zn 0.30 Er x Fe 2-x O 4 (x = 0, 0.01, 0.02, 0.03, 0.04, 0.05) were fabricated using micro-emulsion technique. The substitution of Er was done for the purpose of tuning the optical band gap. Er+3 substituted nanoparticles were annealed at 700 °C for 7 h. A typical composition of Co 0.70 Zn 0.30 Er x Fe 2-x O 4 was utilized to make the nanocomposites material with reduced graphene oxide (rGO), that was prepared by facile chemical route. The main purpose of graphene was to enhance the conductivity of ferrite particles. All these ferrite particles and a composite were characterized by X-rays diffraction (XRD), UV–Visible spectroscopy and SEM for structural elucidation and morphology studies. Single phase spinel structure was confirmed by XRD analysis and crystallized size calculated by Scherer formula was found in the range 35–60 nm. SEM confirmed the well dispersed ferrite particles among graphene sheets. All the Er-substituted ferrite particles were subjected to dielectric parameters study. One typical composition of Co 0.70 Zn 0.30 Er x Fe 2-x O 4 particles and its composites with rGO were utilized for photocatalysis study using methylene blue as model organic compound in the presence of visible light. Current-voltage (I-V) measurements of ferrites nanoparticles and their composites with graphene were also studied. The results of all these techniques were agreed with each other and suggested the various potential applications of these nanoparticles. Highlights • Rare earth Er3+-substituted Cobalt-Zinc Nano-ferrites were prepared. • XRD confirmed the FCC structure of all compositions. • Graphene@ ferrite composites exhibited better photocatalytic properties. [ABSTRACT FROM AUTHOR]

Praseodymium substituted nano crystalline LiCo spinel ferrites with different concentrations were fabricated by micro-emulsion route. TGA, X-ray diffraction and magnetic properties was employed to study the effect of substitution of the Pr on the structure and magnetic parameters. XRD confirmed the formation of the single phase spinel ferrites with minor coexistence of orthophase. The particle size from XRD data was calculated in range from 53 nm to 106 nm. The VSM was employed for magnetic studies between − 10,000 Oe and 10,000 Oe range. Considerable high value of ‘Hc’ coercivity (1581 Oe) and an enhanced value of ‘Ms’ saturation magnetization (51 emu/g) have been obtained as result of substitution. The value of Hc is high enough value but in soft ferrite range. Hence synthesized LiCo 0.5 Pr x Fe 2−x O 4 ferrites are suitable for high density storage devices application. [ABSTRACT FROM AUTHOR]

Nanoparticles of gadolinium (Gd 3+ ) and cobalt (Co 2+ ) doped manganese spinel ferrites have been synthesized by micro-emulsion method. TGA (Thermo gravimetric analysis), XRD (X-ray diffraction), magnetic hysteresis, FTIR (Fourier transform infrared spectroscopy) and dielectric measurements were done to study the variation in manganese ferrite with Co 2+ and Gd 3+ substitution and their effect on lattice parameter and other parameters such as saturation magnetization (Ms), coercivity (Hc) and remanance (Mr). The phase development identified by XRD showed the cubic nature of the fabricated material. The lattice parameter increased due to larger ionic radii of gadolinium and cobalt as compared to iron and manganese. Magnetic properties showed a definite S shaped hysteresis loop at room temperature for all compositions. Overall, the magnetic parameters were increased. This increase could be explained by substitution of Fe 3+ ions with Gd 3+ ions. Gd 3+ ions have very high value of magnetic moment due to seven unpaired electrons. FTIR spectra exhibited two major frequency bands and confirmed cubic spinel structure. The dielectric analysis showed decrease in dielectric loss and dielectric constant with the increase in substitution and frequency. [ABSTRACT FROM AUTHOR]

A comprehensive study on structural, spectral, magnetic and dielectric properties of holmium substituted (Ho 3+ ) lithium ferrites; Li 1.2 Co 0.4 Ho x Fe 2−x O 4 (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 (HoFeO 3 ) were appeared for x ≥ 0.06 indicating the solubility limit of Ho 3+ ions. The lattice constant ′ a′ increased from 8.351 to 8.360 Å upon Ho addition up to x = 0.06 and it decreased thereafter from 8.360 to 8.352 Å. This decrease in lattice constant was attributed to the secondary phase formation revealing segregation of Ho 3+ ions at grain boundaries. The porosity was found to decrease from 44 to 23% by the inclusion of Ho 3+ ions. Fourier transform infrared spectra (FTIR) exhibited tetrahedral ( v 1 ) and octahedral ( v 2 ) 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 ( K o and K t ) were calculated and discussed with the tetrahedral (r A ) and octahedral (r B ) 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 × 10 3 to 5.56 × 10 4 (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 Ho 3+ ions. The maximum value of coercivity (706 Oe) was obtained for Li 1.2 Co 0.4 Ho 0.12 Fe 1.88 O 4 . The improved coercivity may suggest their utilization in perpendicular recording media applications. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The current study is reporting the synthesis and characterization of NiO–Co3O4/rGO nanohybrid for nanocomposite for nonenzymatic glucose sensing. The prepared nanohybrids sample was characterized by X-rays diffraction (XRD), fourier transforms infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The XRD analysis exhibited the cubic crystalline phase for both NiO and Co3O4 in the binary composite. The vibrational mode of NiO and its nanohybrid with reduced graphene oxide (rGO) was defined using FTIR spectral analysis. SEM images of the nanoparticles depicted a non-spherical pattern randomly distributed throughout the whole matrix. The prepared sensor exhibited promising results for glucose sensitivity (345 μA mM) with a wide range of linear response from 1.23 × 10-4 mM to 10 mM and a low limit of detection of 0.13 μM. Further, the interference study was also performed using 100 µM fructose (FR), lactose (LA), uric acid (UA) and ascorbic acid (AA) and results exposed that these interfering species has not affected glucose determination. The obtained results suggested that the nanohybrid has enormous potential to act as a credible sensor for the determination of glucose. [ABSTRACT FROM AUTHOR]

A series of holmium (Ho) doped nanocrystalline Ni 0.7 Zn 0.3 Ho 2x Fe 2–2x O 4 ; 0.0≤x≤0.07 ferrite was synthesized using the conventional ceramic technique. The cubic spinel structure was confirmed by powder X-ray diffraction (XRD). The lattice parameter increases with increase in Ho content due to large ionic radius of Ho 3+ (0.901 Å) as compared to Fe 3+ (0.67 Å). Room temperature DC electrical resistivity and activation energy both increase with the increase of holmium contents. The saturation magnetization (M s ) decreased gradually from 78.92 to 54.17 emu/g due to holmium ions substitution in Ni-Zn ferrites. This decrease in M s is explained on the basis of redistribution of cations amongst the sites and weakening the A-B exchange interactions. An increase in electrical resistivity made this material suitable for its use in high frequency device applications. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A series of nanostructured ferrites having chemical composition Mg 0.7 Co 0.3 Yb x Fe 2− x O 4 ( 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 (ε) 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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A series of nanocrystalline cobalt ferrites doped with yttrium ions were synthesized by chemical co-precipitation technique. The X-ray diffraction analysis reveals that all the samples exhibit cubic spinel phase as main phase along with few traces of orthorhombic phase (YFeO 3 ). The crystallite size calculated by Scherrer’s formula is found in the range of 48–34 nm. This crystallite size is small enough to obtain the suitable signal to noise ratio in the high density recording media applications. The lattice constant was found to decrease from 8.385 Å to 8.348 Å with the increase of yttrium contents which may be attributed to the solubility limit of yttrium ions. The dc electrical resistivity was found to increases from 4.95×10 6 Ω-cm to 8.39×10 7 Ω-cm with the increase of yttrium contents. Yttrium doped samples exhibit lower dielectric constant and dielectric loss tangent as compared to pure CoFe 2 O 4 nanocrystals. An appreciable increase in coercivity has been observed by the Y 3+ addition. The enhanced dc electrical resistivity and coercivity ( H c =1273 Oe) of cobalt nanoparticles (5 wt% doped Y 3+ ) are favorable for their potential use in microwave devices and high density recording media applications. [ABSTRACT FROM AUTHOR]

Abstract: In this work cobalt substituted magnesium zinc nanocrystalline spinel ferrites having general formula Mg0.5Co x Zn0.5−x Fe2O4 where x = 0.1, 0.2, 0.3, 0.4, 0.5 were synthesized using micro-emulsion technique. The Co substituted samples annealed at 700 °C and characterized by various characterization techniques, such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), dielectric measurements and vibrating sample magnetometer (VSM). XRD analysis confirmed single phase spinel structure and the crystalline size calculated by Scherrer's formula found to be in 21.38–45.5 nm range. The lattice constant decreases as substitution of Co is increased. The decrease in lattice constant is attributed to the smaller ionic radius of cobalt as compared to zinc ion. The FTIR spectra reveled two prominent frequency bands in the wave number range 400–600 cm−1 which confirm the cubic spinel structure and completion of chemical reaction. The dielectric parameters were observed to decrease with the increased Co contents. The peaking behavior was observed beyond 1.8 GHz. The frequency dependent dielectric properties of all these nanomaterials have been explained qualitatively in accordance with Koop's phenomenological theory. Magnetic studies revealed that the coercivity (H c ) attains maximum value of 818 Oe at ∼21 nm. The increasing trend of magnetic parameters (coercivity and retentivity) is consistent with crystallinity. The crystallite size is small enough to attain considerable signal to noise ratio in high density recording media. The optimized magnetic parameters suggest that the material with composition Mg0.5Co0.5Fe2O4 may have potential applications in high density recording media. [Copyright &y& Elsevier]

Abstract: Ca–Ni co-substituted samples of nanocrystalline spinel ferrites with chemical formula Mg1−x Ca x Ni y Fe2−y O4 (x=0.0–0.6, y=0.0–1.2) were synthesized by the micro-emulsion method and were annealed at 700°C for 7h. The synthesized samples were characterized by x-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, vibrating sample magnetometry (VSM) and dielectric measurements. The XRD and FTIR analysis reveals that single phase samples can be achieved by substituting Ca and Ni ions at Mg and Fe sites respectively in cubic spinel nano-ferrites. The crystallite size of the synthesized samples was found in the range 29–45nm. The saturation magnetization (M s) increases from 9.84 to 24.99emu/g up to x=0.2, y=0.4 and then decreases, while the coercivity (H c) increases continuously from 94 to 153Oe with the increase in dopants concentration. The dielectric properties of these nano materials were also studied at room temperature in the frequency range 100MHz to 3GHz. The dielectric parameters were found to decrease with the increased Ca–Ni concentration. Further the peaking behavior was observed beyond 1.5GHz. The frequency dependent dielectric properties of all the samples have been explained qualitatively on the basis of the Maxwell–Wagner two-layer model according to Koop's phenomenological theory. The enhanced magnetic parameters and reduced dielectric properties make the synthesized materials suitable for switching and high frequency applications, respectively. [Copyright &y& Elsevier]