Effect of Bi2O3 content on the microstructure and electrical properties of SrBi2Nb2O9 piezoelectric ceramics

Lead-free ceramics, SrBi₂Nb₂O₉–xBi₂O₃ (SBN–xBi), with different Bi contents of which the molar ratio, n(Sr) : n(Bi) : n(Nb), is 1 : 2(1 + x/2) : 2 (x = −0.05, 0.0, 0.05, 0.10), were prepared by conventional solid-state reaction method. The effect of excess bismuth on the crystal structure, microstructure and electrical properties of the ceramics were investigated. A layered perovskite structure without any detectable secondary phase and plate-like morphologies of the grains were clearly observed in all samples. The value of the activation energy suggested that the defects in samples could be related to oxygen vacancies. Excellent electrical properties (e.g., d₃₃ = 18 pC N⁻¹, 2P_r = 17.8 μC cm⁻², ρ_rd = 96.4% and T_c = 420 °C) were simultaneously obtained in the ceramic where x = 0.05. Thermal annealing studies indicated the SBN–xBi ceramics system possessed stable piezoelectric properties, demonstrating that the samples could be promising candidates for high-temperature applications.

Lead-free ceramics, SrBi₂Nb₂O₉–xBi₂O₃ (SBN–xBi), with different Bi contents of which the molar ratio, n(Sr) : n(Bi) : n(Nb), is 1 : 2(1 + x/2) : 2 (x = −0.05, 0.0, 0.05, 0.10), were prepared by conventional solid-state reaction method.     

Annealing effects on the structural and dielectric properties of (Nb + In) co-doped rutile TiO2 ceramics

Density functional theory calculations were conducted to investigate the electronic structures of rutile Ti₁₆O₃₂, Ti₁₃Nb₂InO₃₂, and Ti₁₃Nb₂InO₃₁ systems. High density (Nb + In) co-doped rutile TiO₂ ceramics were successfully prepared by one modified solid state method. XRD, XPS, Raman scattering and FT-IR measurements were performed to investigate the structural properties of the (Nb + In) co-doped rutile TiO₂ ceramics annealed in different atmospheres. The lattice parameters for the (Nb + In) co-doped rutile TiO₂ ceramics were enlarged slightly after they were annealed in air and oxygen. Raman scattering results indicate that the E_g modes are quite sensitive to oxygen vacancy in comparison with the other Raman active modes. The ceramics annealed in oxygen at 873 K exhibit the best dielectric performance with giant dielectric permittivity (>14 000) and small dielectric loss (<0.2) over the frequency range from 40 Hz to 1 MHz.

Density functional theory calculations were conducted to investigate the electronic structures of rutile Ti₁₆O₃₂, Ti₁₃Nb₂InO₃₂, and Ti₁₃Nb₂InO₃₁ systems.     

Luminescence properties of ZnGa2O4:Cr3+,Bi3+ nanophosphors for thermometry applications

Chromium(iii) and bismuth(iii) co-doped ZnGa₂O₄ nanoparticles are synthesized by a hydrothermal method assisted by microwave heating. The obtained nanoparticles, with a diameter smaller than 10 nm, present good luminescence emission in the deep red range centered at 695 nm after coating with a silica layer and calcination at 1000 °C during 2 h. Persistent luminescence and photoluminescence properties are investigated at several temperatures. Bandwidth and luminescence intensity ratio of persistent emission do not present enough change with temperature to obtain a competitive nanothermometer with high sensitivity. Nevertheless, persistent luminescence decay curves present a significant shape change since the trap levels involved in the deexcitation mechanism are unfilled with increase of temperature. Even if the sensitivity reaches 1.7% °C⁻¹ at 190 °C, the repeatability is not optimal. Furthermore, photoluminescent lifetime in the millisecond range extracted from the photoluminescence decay profiles drastically decreases with temperature increase. This variation is attributed to the thermal equilibrium between two thermally coupled chromium(iii) levels (²E and ⁴T₂) that have very different deexcitation lifetimes. For ZnGa₂O₄:Cr³⁺_0.5%,Bi³⁺_0.5%, the temperature sensitivity reaches 1.93% °C⁻¹ at 200 °C. Therefore, this kind of nanoparticle is a very promising thermal sensor for temperature determination at the nanoscale.

Luminescence properties of chromium(iii) and bismuth(iii) co-doped ZnGa₂O₄ nanoparticles are investigated for thermometry applications.     

Optical and dielectric properties of silver-substituted ZnAl2O4 spinels synthesized using a sol-gel auto-combustion method

The present study deals with two compounds, (x = 0.05 and x = 0.1), synthesized using a sol-gel auto-combustion method. X-ray diffraction analysis and Fourier transform infrared spectroscopy confirmed the formation of a spinel structure. UV-visible spectroscopy revealed that the band gap is 4.3 eV and 4 eV for x = 0.05 and x = 0.1, respectively, which confirm that these compounds, (x = 0.05 and x = 0.1), are potential candidates for optoelectronics. Moreover, the effect of frequency and temperature on the dielectric parameters was studied using impedance spectroscopy. Additionally, the activation energies were estimated from the modulus data and are about 0.659 eV for x = 0.05 and 0.41 eV for x = 0.1. These values are in good agreement with those obtained from complex polarizability.

The present study deals with two compounds, (x = 0.05 and x = 0.1), synthesized using a sol-gel auto-combustion method.     

Electrical properties of Sb2O3-modified BiScO3–PbTiO3-based piezoelectric ceramics

Compared with pure Pb-based perovskite ferroelectric materials, BiMeO₃–PbTiO₃ (Me = Sc³⁺, In³⁺, and Yb³⁺) systems have remarkable advantages in their Curie temperatures. As a member of this group, the BiScO₃–PbTiO₃ (BS–PT) solid solution has drawn considerable attention from scientists for its high Curie temperature and excellent piezoelectric coefficient. However, BS–PT ceramics still have some shortcomings, such as high dielectric loss and low mechanical quality factor, which make them unsuitable for high-temperature applications. Herein, we report the effect of the addition of complex ions on the electrical properties of BS–PT ceramics. Sb₂O₃-doped 0.36BiScO₃–0.64PbTi_0.97Fe_0.03O₃ + 1 mol% MnO₂ (BS–PTFMn + x% Sb₂O₃) ceramics were fabricated and their electrical properties were studied. BS–PTFMn + 0.75% Sb₂O₃ had an optimal piezoelectric coefficient, exhibiting which indicates that Sb₂O₃ doping can improve the piezoelectric properties of the BS–PT ceramics, exhibiting a “soft” effect of Sb₂O₃ doping. In addition, the thermal depolarization temperature (T_d) of BS–PTFMn + 0.75% Sb₂O₃ ceramics remained above 300 °C, such as 325 °C for BS–PTFMn + 0.75% Sb₂O₃. It was concluded that the piezoelectric properties of BS–PT ceramics were enhanced by the addition of Sb₂O₃.

Compared with pure Pb-based perovskite ferroelectric materials, BiMeO₃–PbTiO₃ (Me = Sc³⁺, In³⁺, and Yb³⁺) systems have remarkable advantages in their Curie temperatures.     

Enhanced dielectric properties with a significantly reduced loss tangent in (Mg2+, Al3+) co-doped CaCu3Ti4O12 ceramics: DFT and experimental investigations

CaCu₃Ti₄O₁₂ and CaCu_2.95Mg_0.05Ti_3.95Al_0.05O₁₂ ceramics were fabricated via a solid-state reaction method. A single-phase of CaCu₃Ti₄O₁₂ was found in these two ceramics. Very great grain size expansion was produced by co-doping with Mg²⁺ and Al³⁺. DFT results indicate that both Mg and Al atoms preferentially occupy Cu sites, creating liquid-phase sintering decomposition at grain boundary layers. Very high dielectric permittivity of ∼58 397 and low loss tangent of about 0.047 were achieved in a CaCu_2.95Mg_0.05Ti_3.95Al_0.05O₁₂ ceramic. Additionally, the temperature stability of the dielectric response was improved. Better dielectric properties in the co-doped ceramic have possible origins from enhanced grain boundary responses, especially from the influences of metastable phases and oxygen enrichment at the grain boundaries. Experimental and computational results indicate that the colossal dielectric properties in CaCu₃Ti₄O₁₂ ceramics might be correlated with an internal barrier layer capacitor structure.

Mg and Al atoms preferentially occupy Cu sites, creating liquid-phase sintering decomposition at grain boundary layers. This results in very high dielectric permittivity and a low loss tangent of the CaCu_2.95Mg_0.05Ti_3.95Al_0.05O₁₂ ceramic.     

Sensitive MnFe2O4–Ag hybrid nanoparticles with photothermal and magnetothermal properties for hyperthermia applications

In this study, we present an experiment showing that designing multifunctional MnFe₂O₄–Ag nanoparticles to act as a dual hyperthermia agent is an efficient route for enhancing their heating ability. Interestingly, the specific absorption rate of the heteromeric MnFe₂O₄–Ag nanoparticles increased 2.7 times under simultaneous irradiation of a 100 Oe magnetic field and 0.14 W cm⁻² laser compared to the action by the magnetic field alone, and more interestingly, is 30% higher than the sum of the two individual actions. The synergistic benefit of the magneto- and photo-thermal properties of the heteromeric structure can reduce the strengths of the magnetic field and laser intensities as well as their irradiation time to levels lower than those required in their hyperthermia applications individually. In vitro cytotoxicity analysis performed on HepG2 liver cancer and Hela cervical cancer cell lines showed that IC₅₀ values were 83 ± 5.6 μg mL⁻¹ (for HepG2) and 122.6 ± 19.8 μg mL⁻¹ (for Hela cells) after 48 h of incubation, therefore, the nanoparticles are moderately cytotoxic and nontoxic to HepG2 and Hela cells, respectively; which offers the potential of safe therapy.

In this study, we present an experiment showing that designing multifunctional MnFe₂O₄–Ag nanoparticles to act as a dual hyperthermia agent is an efficient route for enhancing their heating ability.     

Structure,dielectric, and piezoelectric properties of K0.5Na0.5NbO3-based lead-free ceramics

Lead-free ceramics based on the (1 − x)K_0.5Na_0.5NbO₃–xBi(Zn_0.5Ti_0.5)O₃ (KNN–BZT) system obtained via the conventional solid-state processing technique were characterized for their crystal structure, microstructure, and electrical properties. Rietveld analysis of X-ray diffraction data confirmed the formation of a stable perovskite phase for Bi(Zn_0.5Ti_0.5)O₃ substitutions up to 30 mol%. The crystal structure was found to transform from orthorhombic Amm2 to cubic Pm$\bar{3}$m through mixed rhombohedral and tetragonal phases with the increase in Bi(Zn_0.5Ti_0.5)O₃ content. Temperature-dependent dielectric behavior indicated an increase in diffuseness of both orthorhombic to tetragonal and tetragonal to cubic phase transitions as well as a gradual shift towards room temperature. The sample with x ≈ 0.02 exhibited a mixed rhombohedral and orthorhombic phase at room temperature. A high-temperature X-ray diffraction study confirmed the strong temperature dependence of the phase coexistence. The sample with the composition 0.98(K_0.5Na_0.5NbO₃)–0.02(BiZn_0.5Ti_0.5O₃) showed an improved room temperature piezoelectric coefficient d₃₃ = 109 pC/N and a high Curie temperature T_C = 383 °C.

Room temperature powder X-ray diffraction patterns of (1 – x)K_0.5Na_0.5NbO₃–xBi(Zn_0.5Ti_0.5)O₃ system.     

Laser heating of dielectric particles for medical and biological applications

We consider the general problem of laser pulse heating of a spherical dielectric particle embedded in a liquid. The discussed range of the problem parameters is typical for medical and biological applications. We focus on the case, when the heat diffusivity in the particle is of the same order of magnitude as that in the fluid. We perform quantitative analysis of the heat transfer equation based on interplay of four characteristic scales of the problem, namely the particle radius, the characteristic depth of light absorption in the material of the particle and the two heat diffusion lengths: in the particle and in the embedding liquid. A new quantitative characteristic of the laser action, that is the cooling time, describing the temporal scale of the cooling down of the particle after the laser pulse is over, is introduced and discussed. Simple analytical formulas for the temperature rise in the center of the particle and at its surface as well as for the cooling time are obtained. We show that at the appropriate choice of the problem parameters the cooling time may be by many orders of magnitude larger the laser pulse duration. It makes possible to minimize the undesirable damage of healthy tissues owing to the finite size of the laser beam and scattering of the laser radiation, simultaneously keeping the total hyperthermia period large enough to kill the pathogenic cells. An example of application of the developed approach to optimization of the therapeutic effect at the laser heating of particles for cancer therapy is presented.OCIS codes: (350.4990) Particles, (170.1610) Clinical applications     

Structural,optical and dielectric properties of tellurium-based double perovskite Sr2Ni1−xZnxTeO6

In this paper, Sr₂Ni_1−xZn_xTeO₆ (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) double perovskite compounds were synthesised by the conventional solid-state method, and the structural, optical and dielectric properties were investigated. The Rietveld refinement of X-ray diffraction data shows that all compounds were crystallised in monoclinic symmetry with the I2/m space group. Morphological scanning electron microscopy reported that the grain sizes decreased as the dopant increased. The UV-vis diffuse reflectance spectroscopy conducted for all samples found that the optical band gap energy, E_g, increased from 3.71 eV to 4.14 eV. The dielectric permittivity ε′ values increased for the highest Zn-doped composition, Sr₂Ni_0.2Zn_0.8TeO₆, being ∼1000 and ∼60 in the low- and high-frequency range, respectively. All samples exhibited low dielectric loss (tan δ ≤ 0.20) in the range of 10⁴–10⁵ Hz frequency. Impedance measurement revealed that grain resistance decreased with enhancement in Zn content in the Sr₂NiTeO₆ crystal lattice.

In this paper, Sr₂Ni_1−xZn_xTeO₆ (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) double perovskite compounds were synthesised by the conventional solid-state method, and the structural, optical and dielectric properties were investigated.     

Correction: Sensitive MnFe2O4–Ag hybrid nanoparticles with photothermal and magnetothermal properties for hyperthermia applications

Correction for ‘Sensitive MnFe₂O₄–Ag hybrid nanoparticles with photothermal and magnetothermal properties for hyperthermia applications’ by T. T. N. Nha et al., RSC Adv., 2021, 11, 30054–30068. DOI: 10.1039/D1RA03216J

The authors regret that an incorrect grant number was shown in the acknowledgements section of the published article. The corrected section should read:This work was supported by the Vietnam Academy of Science and Technology (VAST) by Program of Development in the field of Physics by 2020 under grant number KHCBVL.02/20-21, and partly by AOARD Award No. FA2386-17-1-4042.The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers.     

Structural,optical and dielectric properties of Cu1.5Mn1.5O4 spinel nanoparticles

In this study, a Cu_1.5Mn_1.5O₄ spinel was successfully synthesized by a sol–gel method at 500 °C for 5 h and characterized by different techniques. X-ray diffraction (XRD), Fourier transformation infrared (FTIR) spectroscopy and Raman spectroscopic analyses confirmed the formation of a spinel cubic structure with the Fd$\bar{3}$m space group. The SEM proves that the grain size of our compound is of the order of 48 nm. Crystallite sizes determined from three estimates are closer to the grain size obtained from the SEM, indicating the single domain nature of the sample. The optical properties of UV-visible spectroscopy for our sample showed that the gap value is equal to 3.82 eV, making our compound a good candidate for optoelectronic applications. For electrical properties, impedance spectroscopy was performed at a frequency range of 40 ≤ frequency ≤ 10⁶ Hz. This suggested hoping conduction due to three theoretical models. The latter can be attributed to the correlated barrier hopping (CBH) model in region I, overlapping large polaron tunneling (OLPT) in region II and non-overlapping small polaron tunneling (NSPT) mechanism in region III. One dielectric relaxation is detected from the dielectric impedance and modulus, attributed to grain contributions. This behavior was confirmed by both Nyquist and Argand''s plots of dielectric impedance at different measuring temperatures.

In this study, a Cu_1.5Mn_1.5O₄ spinel was successfully synthesized by a sol–gel method at 500 °C for 5 h and characterized by different techniques.     

Preparation and electrical properties of inorganic electride [Y2Ti2O6]2+(2e−)

Oxygen-depleted samples [Y₂Ti₂O_7−x]^2x+(2xe⁻) (0 ≤ x ≤ 1.0) were prepared by reducing Y₂TiO₇ powders at 500 °C to 650 °C using CaH₂ as a reductive agent, where x represents the content of , which was determined by thermogravimetric analysis. Powder X-ray diffraction patterns illustrate that the pure pyrochlore phase is kept for the samples with x ≤ 1.0, whereas the apparent x values surpass 1.0, and the impurity phase Y₂O₃ appears. The electride [Y₂Ti₂O_7−x]^2x+(2xe⁻) (x ≈ 1.0) can be obtained under a reductive condition, in which the concentration of V_O is 7.75 × 10²¹ cm⁻³. The electron paramagnetic resonance measurements gave the concentration of unpaired electrons in the electride as 1.30 × 10²¹ cm⁻³, indicating that the degree of the ionization of is less than 10%. Conductivity measurements for a sintered pellet sample (relative density ∼ 70%) indicate that the electride has quite high conductivity (∼1.09 S cm⁻¹ at 300 K). The conduction was interpreted by using the variable range hopping mechanisms.

Electride [Y₂Ti₂O₆]²⁺(2e⁻) was prepared by solid reducing processes, which was characterized by XRD, TG and EPR. The electride has high conductivity (1.09 S cm⁻¹ at 300 K).     

Electrical conductivity and dielectric properties of Sr doped M-type barium hexaferrite BaFe12O19

The hexaferrite Ba_1−xSr_xFe₁₂O₁₉ compounds with x = 0, 0.5 and 1 were synthesized by the autocombustion method. X-ray diffraction (XRD), Raman spectroscopy and transmission electron microscopy (TEM) were used for structural and morphological studies.

The hexaferrite Ba_1−xSr_xFe₁₂O₁₉ compounds with x = 0, 0.5 and 1 were synthesized by the autocombustion method.

The Raman results showed that the intensity of the resonance band remains unchanged in Ba_1−xSr_xFe₁₂O₁₉ compared to the undoped compound (x = 0) indicating that the polarizability did not change during the vibrations. The particle sizes, observed by TEM, are reduced from 228 nm to 176 nm with doping.Electrical conductance measurements show that all samples present semiconductor-like behaviors. The Maxwell–Wagner model explains why the alternating electrical conductivity of the samples doped with Sr is lower compared to that of the undoped sample. The Correlated Barrier Hopping (CBH) model dominates the conduction process for the BaFe₁₂O₁₉ sample, whereas the No overlapping Small Polaron Tunneling (NSPT) model dominates the conduction process for the Ba_0.5Sr_0.5Fe₁₂O₁₉ sample. For SrFe₁₂O₁₉ the conduction is dominated by the NSPT model at temperatures below 240 K and by the CBH model above 240 K. The BaFe₁₂O₁₉ compound exhibits a giant dielectric constant (ε′) whose values reached 10⁴ at low frequencies. This value is reduced to 150 in the Sr-doped hexaferrite.     

Improved microstructure and significantly enhanced dielectric properties of Al3+/Cr3+/Ta5+ triple-doped TiO2 ceramics by Re-balancing charge compensation

The charge compensation mechanism and dielectric properties of the (Al_xCr_0.05−x)Ta_0.05Ti_0.9O₂ ceramics were studied. The mean grain size slightly changed with the increase in the Al³⁺/Cr³⁺ ratio, while the porosity was significantly reduced. The dielectric permittivity of the co-doped Cr_0.05Ta_0.05Ti_0.9O₂ ceramic was as low as ε′∼ 10³, which was described by self-charge compensation between Cr³⁺–Ta⁵⁺, suppressing the formation of Ti³⁺. Interestingly, ε′ can be significantly increased (6.68 × 10⁴) by re-balancing the charge compensation via triple doping with Al³⁺ in the Al³⁺/Cr³⁺ ratio of 1.0, while a low loss tangent (∼0.07) was obtained. The insulating grains of [Cr_0.05³⁺Ta_0.05⁵⁺]Ti_0.9⁴⁺O₁₂ has become the semiconducting grains for the triple-doped Al_x³⁺[Cr_0.05−x³⁺Ta_0.05−x⁵⁺][Ta_x⁵⁺Ti_x³⁺Ti_0.9+x⁴⁺]O_12+3x/2. Considering an insulating grain with low ε′ of the Cr_0.05Ta_0.05Ti_0.9O₂ ceramic, the electron-pinned defect-dipoles and interfacial polarization were unlikely to exist supported by the first principles calculations. The significantly enhanced ε′ value of the triple-doped ceramic was primarily contributed by the interfacial polarization at the interface between the semiconducting and insulating parts, which was supported by impedance spectroscopy. This research gives an underlying mechanism on the charge compensation in the Al³⁺/Cr³⁺/Ta⁵⁺-doped TiO₂ system for further designing the dielectric and electrical properties of TiO₂-based ceramics for capacitor applications.

The dielectric properties of Cr³⁺/Ta³⁺ co-doped TiO₂ can be significantly improved by triple doping with Al³⁺ due to the re-balance of charge compensation.     

Colossal dielectric permittivity,reduced loss tangent and the microstructure of Ca1−xCdxCu3Ti4O12−2yF2y ceramics

Ca_1−xCd_xCu₃Ti₄O_12−2yF_2y (x = y = 0, 0.10, and 0.15) ceramics were successfully prepared via a conventional solid-state reaction (SSR) method. A single-phase CaCu₃Ti₄O₁₂ with a unit cell ∼7.393 Å was detected in all of the studied ceramic samples. The grain sizes of sintered Ca_1−xCd_xCu₃Ti₄O_12−2yF_2y ceramics were significantly enlarged with increasing dopant levels. Liquid-phase sintering mechanisms could be well matched to explain the enlarged grain size in the doped ceramics. Interestingly, preserved high dielectric permittivities, ∼36 279–38 947, and significantly reduced loss tangents, ∼0.024–0.033, were achieved in CdF₂ codoped CCTO ceramics. Density functional theory results disclosed that the Cu site is the most preferable location for the Cd dopant. Moreover, F atoms preferentially remained close to the Cd atoms in this structure. An enhanced grain boundary response might be a primary cause of the improved dielectric properties in Ca_1−xCd_xCu₃Ti₄O_12−2yF_2y ceramics. The internal barrier layer capacitor model could well describe the colossal dielectric response of all studied sintered ceramics.

CdF₂ defect clusters result in enhancement of dielectric properties of the Ca_1−xCd_xCu₃Ti₄O_12−2yF_2y ceramics.     

The preparation,microstructure and mechanical properties of a dense MgO–Al2O3–SiO2 based glass-ceramic coating on porous BN/Si2N2O ceramics

A dense MgO–Al₂O₃–SiO₂ based glass-ceramic coating was prepared by a doctor blade process on a porous BN/Si₂N₂O ceramic surface followed by heat treatment at 1050 °C under nitrogen flow. The phase composition, microstructure, mechanical properties and water absorption of the coating were studied. The coating consisted of α-cordierite phase with a small amount of glass phase. The dense coating without pores and cracks was favorable to seal and densify the porous ceramic surface due to part of the molten glass infiltrating the surface pores. The coating was defect-free and tightly bonded to the substrate because of a larger bonding area between the coating and the substrate. The elastic modulus and bending strength of the glass-ceramic coating were 37.9 GPa and 67.1 MPa, respectively. Moreover, the coated samples had a high Vickers hardness and low water absorption.

A dense MgO–Al₂O₃–SiO₂ based glass-ceramic coating was prepared by a doctor blade process on a porous BN/Si₂N₂O ceramic surface followed by heat treatment at 1050 °C under nitrogen flow.     

Design and synergistic effect of nano-sized epoxy-NiCo2O4 nanocomposites for anticorrosion applications

In the present work, we evaluated the corrosion inhibition properties of a ligand and mixed metal oxide nanocomposite. The ligand and mixed nickel–cobalt complex were synthesized using 1-naphthoic acid and aminoguanidine with the formulae [C₁₁H₇O₂(CN₄H₅)(CN₄H₆)]·H₂O and {Ni–Co[(CH₅N₄)₂(C₁₁H₇O₂)₂]}·H₂O, respectively. After their synthesis, physicochemical techniques such as CHNS analysis, infrared and UV-visible spectroscopy, thermal analysis, and X-ray diffraction (XRD) were employed to characterize both the synthesized ligand and nickel–cobalt complex. The metal oxide prepared from the decomposition of the metal complex was also characterized using several techniques to confirm its bonding and structure. In addition, the corrosion inhibition efficiency of the epoxy-ligand and epoxy-NiCo₂O₄ nanocomposite on mild steel (MS) in 3 M hydrochloric acid (HCl), 1.5 M sulfuric acid (H₂SO₄), and 0.5 M phosphoric acid (H₃PO₄) solution was examined and compared using weight loss measurements, Tafel plots, isotherms and electrochemical impedance spectroscopy (EIS). The results from the electrochemical studies disclosed that the epoxy coating of mixed metal oxides with 0.8 ppm concentration yielded excellent corrosion protection. The SEM images of mild steel and mild steel coated with epoxy-ligand/epoxy-NiCo₂O₄ in HCl confirmed the anti-corrosive behavior of the synthesized compounds. Hence, the as-prepared material can be a next-generation tool for sustainable anti-corrosive coatings.

This study reports the synthesis of nano-sized epoxy-NiCo₂O₄ nanocomposites and their anti-corrosive efficiency to attain sustainable development.     

Improved electrical transport properties of polycrystalline La0.8(Ca0.12Sr0.08)MnO3 ceramics by Ag2O doping

Polycrystalline La_0.8(Ca_0.12Sr_0.08)MnO₃:mol%Ag_x (LCSMO:Ag_x, x = 0, 0.1, 0.2, 0.3 and 0.4) ceramics were synthesized by the sol–gel technique. Structural, electrical and magnetic properties of the LCSMO:Ag_x ceramics were investigated in detail. X-ray diffraction (XRD) data analyses revealed that all the samples were crystalized in the orthorhombic structure with space group of Pnma. With the increase in Ag doping (x), the grain sizes of the LCSMO:Ag_x samples increased and the amount of grain boundaries (GBs) decreased accordingly. At the same time, the Mn–O bond distance and the Mn–O–Mn bond angles changed correspondingly, leading to the slight increase in the lattice constants (a, b and c) and slight expansion of cell volume (V). For the LCSMO:Ag_x sample with x = 0.3, the optimal values of temperature coefficient of resistivity (TCR) and magnetoresistance (MR) reached 16.22% K⁻¹ (265.1 K) and 42.07% K⁻¹ (270.48 K), respectively. In addition, the fitting analysis of ρ–T curves showed that the experimental data were consistent with the theoretical calculation data. In the T < T_MI (metal-insulator transition temperature) region, the electrical conduction mechanism of LCSMO:Ag_x was clarified by electron-magnon, electron–electron and electron-phonon scattering. In the T > T_MI region, the resistivity data were interpreted by using the adiabatic small-polaron hopping model. Furthermore, in the entire temperature range, the phenomenological equation called the percolation model was used to explain the resistivity data and the phase-separation mechanism of ferromagnetic metallic (FM) and paramagnetic insulating (PI) phases. All the obtained results indicated that the improvement in the electrical properties of the LCSMO:Ag_x samples was attributed to the doping of Ag, which changed the A-site (La, Ca and Sr ions) average ion radius, the Mn–O–Mn bond angles and the Mn–O bond distance. In addition, the grain size increased, which led to improvement in the Mn⁴⁺ ion concentration and the GBs connectivity in the LCSMO:Ag_x polycrystalline ceramics.

Polycrystalline La_0.8(Ca_0.12Sr_0.08)MnO₃:mol%Ag_x (LCSMO:Ag_x, x = 0, 0.1, 0.2, 0.3 and 0.4) ceramics were synthesized by the sol–gel technique.     

Investigation of BaO reinforced TiO2–p2O5–li2O glasses for optical and neutron shielding applications

The optical and radiation shielding characteristics of 15TiO₂-70P₂O₅ – (15 − x) Li₂O-x BaO x = (0 ≤ x ≤ 10 mol%) glasses were reported in this study. The glass status of the investigated samples was established by XRD. Although the molar volume decreases within 39.8–31.2 cm³ mol⁻¹, the density was increased from 2.908 to 4.11 g cm⁻³ with the addition of BaO. UV-Vis-NIR spectroscopy was utilized for the examination of the optical characteristics of all compositions. E^indir_opt. and E^dir_opt. both increased from 2.7 to 3.07 eV and 2.79 to 3.31 eV, while E_u decreased from 0.368 to 0.295 eV. Furthermore, the Phy-X/PSD code was used to evaluate the gamma-ray shielding parameter. Within the energy range of 15 keV to 15 MeV, the equivalent atomic number, as well as the EBF and EABF parameters, was evaluated. Overall, excellent material properties were detected for a glass with a high BaO content, which could be useful for future optical, shielding, and fast neutron shielding properties.

The optical and radiation shielding characteristics of 15TiO₂–70P₂O₅ – (15 − x) Li₂O-x BaO x = (0 ≤ x ≤ 10 mol%) glasses were reported in this study.