The calorimetry and thermodynamic functions of Nd Mg<Stack><Subscript>3</Subscript><Superscript>I</Superscript></Stack>Mn<Subscript>4</Subscript>O<Subscript>12</Subscript> (Me<Superscript>I</Superscript>-Li,Na, K) manganites in the range from 298.15 to 673 K

The ceramic technology is employed for synthesizing manganites of composition Nd Mg ₃ ^I Mg₃Mn₄O₁₂(Me^I-Li, Na, K). The X-ray technique is used to find that the compounds crystallize in tetragonal syngony. The parameters of their crystal lattices are determined. Their heat capacities are experimentally determined in the range from 298.15 to 673 K, which enables one to reveal second-order phase transitions. In view of these transitions, equations describing the C _p ^° ～ f(T) dependence are derived, and the thermodynamic functions C _p ^° (T), H°(T)-H°(298.15), S°(T), and Φ ^xx (T) are calculated.     

Heat Capacity and thermodynamic functions of DyMe<Superscript>II</Superscript>Cr<Subscript>2</Subscript>O<Subscript>5.5</Subscript>(Me<Superscript>II</Superscript>-Mg,Ca) in the range from 298.15 to 673 K

The calorimetric method is used to investigate the heat capacity of DyMe^IICr₂O_5.5(Me^II-Mg, Ca) chromites in the range from 298.15 to 673 K. The C _p ⁰ ～ f(T) curves exhibit λ-like effects at 348 and 548 K for DyMgCr₂O_5.5 and at 473 K for DyCaCr₂O_5.5, which apparently relate to second-order phase transitions. The temperature dependences are calculated for thermodynamic functions C _p ⁰ (T), H ⁰(T)-H ⁰(298.15), S ⁰(T), and Φ**(T).     

Effect of Al Substitution in Structural and Magnetic Properties of MnCr<Subscript>2</Subscript>O<Subscript>4</Subscript>

Single-phase samples of Mn(Cr_1?x Al _x )₂O₄ (x = 0 – 0.30) with cubic spinel structure were prepared and the lattice constant is found to decrease from a = 8.4396 Å for x = 0 to a = 8.3801 Å for x = 0.30. The substitution of Al at Cr site is confirmed from the blue shift of Raman modes. Magnetization measurements and analysis show all the prepared samples exhibit ferrimagnetic transition with transition temperature in the range of 46 K for x = 0 to 33 K for x = 0.30. The saturation magnetization (M _s ) and the estimated anisotropy constant (K) show an anomalous behavior up to x = 0.10 and beyond that they decrease monotonously. They are explained by considering different site preferences of Al ³⁺ ions as the doping concentration is increased. The theoretical and experimental effective magnetic moment of the samples is found to be comparable and it decreases with increase in Al concentration.     

The Effect of Annealing on Phase Stability and Magnetic Properties of Hexaferrite BaFe<Subscript>12</Subscript><Emphasis Type="Italic">O</Emphasis><Subscript>19</Subscript>

The hexaferrite BaFe₁₂ O ₁₉ phase was synthesized through the mechanical alloying process followed by subsequent annealing. Rietveld refinements of as-milled powder annealed at 700 ^°C confirm the formation of the BaFe₁₂ O ₁₉ phase with the presence of an important amount of the α-Fe₂ O ₃ phase. Thus, prior mechanical milling shows much lower reaction temperature and less reaction time compared to conventional methods. Further annealing up to 900 and 1100 ^°C could not enable the formation of a single BaFe₁₂ O ₁₉ phase, reaching an optimum phase composition ratio close to BaFe₁₂ O ₁₉/ α-Fe₂ O ₃ 70/30. The crystallite size was found to be in the nanoscale level but increases with increasing temperature (BaFe₁₂ O ₁₉ = 20–62 nm; α-Fe₂ O ₃ = 31–74 nm). SEM micrographs show that as the annealing temperature rises, the particles become more regular with sharp edges and hexagonal-like shapes. Magnetic measurements reveal that both M _s and M _r increase with annealing temperature to reach maximum values at 900 ^°C then remain unchanged, associated with phase composition. The coercivity H _c increases upon annealing up to 700 ^°C to a much higher value, from 1.7 kOe for as-milled powder to 4.8 kOe. Its value then decreases, attributed to grain (particle) growth (formation of larger particles) due to high annealing temperatures: 900–1100 ^°C. The obtained composites show very interesting magnetic properties and can be considered for potential applications, such as hyperthermia, heavy metal and dye removal, and hard/soft magnetic composites.     

Studies of the Local Structure and the g Factors of the Cu<Superscript>2+</Superscript> Site in Y<Subscript>2</Subscript>BaCuO<Subscript>5</Subscript>

The local structure and the g factors (g _x , g _y , and g _z ) of the Cu²⁺ site in Y₂BaCuO₅ are theoretically studied using the perturbation formulas of the g factors for a 3d⁹ ion in orthorhombically elongated octahedra. The orthorhombic field parameters in these formulas are determined from the superposition model and the local geometry of the system. From the calculations, the oxygen octahedron is found to undergo the local elongation ΔZ (≈0.05 Å) along c-axis and the relative bond length variation ΔX (≈0.1 Å) along a- and b-axes, respectively. The calculated g factors based on the above local structure are in good agreement with the experimental data. The relationships between the anisotropies of the g factors and the low symmetrical (orthorhombic) distortions of the Cu²⁺ site in Y₂BaCuO₅ are discussed.     

Critical Behavior of La<Subscript>0.67</Subscript>Ba<Subscript>0.33</Subscript>Mn<Subscript>0.95</Subscript>Fe<Subscript>0.05</Subscript>O<Subscript>3</Subscript> Manganite

The critical behavior of perovskite manganite La_0.67Ba_0.33Mn_0.95Fe_0.05O₃ at the ferromagnetic–paramagnetic has been analyzed. The results show that the sample exhibited the second-order magnetic phase transition. The estimated critical exponents derived from the magnetic data using various such as modified d’Arrott plot Kouvel–Fisher method and critical magnetization M(T _C, H). The critical exponents values for the La_0.67Ba_0.33Mn_0.95Fe_0.05O₃ are close to those expected from the mean field model β = 0.504 ± 0.01 with T _C = 275661 ± 0.447 (from the temperature dependence of the spontaneous magnetization below T _C ), γ = 1.013 ± 0.017 with T _C = 276132 ± 0.452 (from the temperature dependence of the inverse initial susceptibility above T _C ), and δ = 3.0403 ± 0.0003. Moreover, the critical exponents also obey the single scaling equation of M(H, ε) = |ε| ^β f _±(H/|ε| ^β+γ ).     

Compounds WAl<Subscript>4</Subscript>, WAl<Subscript>3</Subscript>, W<Subscript>3</Subscript>Al<Subscript>7</Subscript>, and WAl<Subscript>2</Subscript> and Al-W-N combustion products

X-ray diffraction data are presented for combustion products in the Al-W-N system. New, nonequilibrium intermetallic compounds have been identified, their diffraction patterns have been indexed, and their unit-cell parameters have been determined. The phases α-and β-WAl₄ are shown to exist in three isomorphous forms, differing in unit-cell centering. The phases α′-, α″-, and α?-WAl₄ are monoclinic, with a ₀ = 5.272 Å, b ₀ = 17.770 Å, c ₀ = 5.218 Å, β = 100.10°; point groups C12/c1, A12/n1, I12/a1, respectively. The phases β′-, β″-, and β?-WAl₄ are monoclinic, with a ₀ = 5.465 Å, b ₀ = 12.814 Å, c ₀ = 5.428 Å, β = 105.92°; point groups A112/m, B112/m, I112/m, respectively. The compounds WAl₂ and W₃Al₇, identified each in two isomorphous forms, differ in cell metrics (doubling) but possess the same point group: P222. WAl ₂ ^′ : orthorhombic, a ₀ = 5.793 Å, b ₀ = 3.740 Å, c ₀ = 6.852 Å. WAl ₂ ^″ : orthorhombic, a ₀ = 11.586 Å, b ₀ = 3.740 Å, c ₀ = 6.852 Å. W₃Al ₇ ^′ : orthorhombic, Pmm2, a ₀ = 6.225 Å, b ₀ = 4.806 Å, c ₀ = 4.437 Å. W₃Al ₇ ^″ : orthorhombic, Pmm2, a ₀ = 12.500 Å, b ₀ = 4.806 Å, c ₀ = 8.874 Å. The new phase WAl₃: triclinic, P1, a ₀ = 8.642 Å, b ₀ = 10.872 Å, c ₀ = 5.478 Å, α = 104.02°, β = 64.90°, γ = 107.15°.     

Synthesis and characterization of ternary compound,Mn<Subscript>2</Subscript>SnTe<Subscript>4</Subscript>

Mn₂SnTe₄ was synthesized by direct fusion using the anneal method. X-ray powder diffraction analysis indicated that this material crystallizes in the olivine-type structure, space group Pnma, Z = 4, with unit cell parameters: a = 14.020(2) Å, b = 8.147(1) Å, c = 6.607(1) Å, V = 754.7(2) ų. The Rietveld refinement converged to the figures of merit, R _p = 6.9%, R _wp = 8.5%, R _exp = 6.0%, χ² = 2.0 and S = 1.4.     

Synthesis and characterization of <Emphasis Type="Italic">Eichhornia</Emphasis>-mediated copper oxide nanoparticles and assessing their antifungal activity against plant pathogens

In this paper, we report the biosynthesis and characterization of copper oxide nanoparticles from an aquatic noxious weed, Eichhornia crassipes by green chemistry approach. The aim of this work is to synthesize copper oxide nanoparticles by simple, cost-effective and ecofriendly method as an alternative to other available techniques. The synthesized copper oxide nanoparticles were characterized by UV–visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), Field emission scanning electron microscopy (FESEM) and Energy dispersive X-ray spectroscopy (EDX) analyses. The synthesized particles were highly stable, spherical in shape with an average diameter of 28 ± 4 nm. The synthesized nanoparticles were then explored to antifungal activity against plant pathogens. Highest zone of inhibition were observed in 100 μg ml ^{? 1} of Eichhornia-mediated copper oxide nanoparticle against Fusarium culmorum and Aspergillus niger. This Eichhornia-mediated copper oxide nanoparticles were proved to be good antifungal agents against plant fungal pathogens.     

Investigation of Magnetic,Magnetocaloric, and Critical Properties of La<Subscript>0.5</Subscript>Ba<Subscript>0.5</Subscript>MnO<Subscript>3</Subscript> Manganite

We present an extensive study of the magnetic properties of a novel La_0.5Ba_0.5MnO₃ perovskite material prepared by the hydrothermal method. The explored sample was structurally studied by the x-ray diffraction (XRD) method which confirms the formation of a pure cubic phase of a perovskite structure with Pm3m space group. The magnetic properties were probed by employing temperature M (T) and external magnetic field M (μ_oH) dependence of magnetization measurements. A magnetic phase transition from ferromagnetic to paramagnetic phase occurs at 339 K in this sample. The maximum magnetic entropy change (\(\left | {{\Delta } S}_{M}^{\max } \right |\)) took a value of 1.4 J kg^??1 K^??1 at the applied magnetic field of 4.0 T for the explored sample and has also been found to occur at Curie temperature (T_C). This large entropy change might be instigated from the abrupt reduction of magnetization at T_C. The magnetocaloric effect (MCE) is maximum at T_C as represented by M (μ_oH) isotherms. The relative cooling power (RCP) is 243.2 J kg^??1 at μ_oH =?4.0 T. Moreover, the critical properties near T_C have been probed from magnetic data. The critical exponents δ, β, and γ with values 3.82, 0.42, and 1.2 are close to the values predicted by the 3D Ising model. Additionally, the authenticity of the critical exponents has been confirmed by the scaling equation of state and all data fall on two separate branches, one for T < T_C and the other for T > T_C, signifying that the critical exponents obtained in this work are accurate.     

Improvement of the Magnetization of Barium Hexaferrites Induced by Substitution of Nd<Superscript>3+</Superscript> Ions for Fe<Superscript>3+</Superscript> Ions

Barium hexagonal ferrites (BaNd _x Fe_12?x O ₁₉) have been synthesized by initial high-energy milling of the precursors and calcining subsequently. The as-prepared samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and vibrating sample magnetometry (VSM). XRD and SEM examinations reveal that a high-crystallized hexagonal BaNd _x Fe_12?x O ₁₉ with lamellar morphology is obtained when the precursor is calcined at 1200^°C in air for 3 h. The hexagonal crystalline structure of BaFe₁₂ O ₁₉ is not changed after doping Nd³⁺ ions in BaFe₁₂ O ₁₉. However, lattice parameters a and b values increase with an increase in Nd content at first, then decrease. Nd substitution may improve the magnetic properties of BaNd _x Fe_12?x O ₁₉. BaNd_0.1Fe_11.9 O ₁₉, obtained at 1050^°C, has the highest specific saturation magnetization value (80.81 emu/g) and magnetic moment (16.21 μ _B); BaNd_0.2Fe_11.8 O ₁₉, obtained at 950^°C, has the highest coercivity value, 4075.19 Oe.     

Optimized chromatographic separation and biological evaluation of <Superscript>99<Emphasis Type="Italic">m</Emphasis> </Superscript>Tc-clarithromycin for infective inflammation diagnosis

Clarithromycin antibiotic was labeled with technetium-99m by adding ^99mTc to clarithromycin in the presence of SnCl₂·2H₂O. The radiochemical yield of ^99mTc-clarithromycin was determined by chromatographic methods. Gel chromatographic method was investigated for separation of the reaction mixture using different eluents including NaCl and phosphate, citrate, and carbonate buffer solutions. Also, free ^99mTcO₄^- and ^99mTc-clarithromycin were efficiently separated by reversed-phase HPLC on RP18 column. The maximum radiochemical yield reached 98 ± 0.2%. ^99mTc-clarithromycin is stable for 6 h. Biological distribution of ^99mTc-clarithromycin was studied for mice with the infection in the left thigh induced using Staphylococcus aureus. The target-to-nontarget (T/NT) ratio for ^99mTc-clarithromycin was found to be 7.33 ± 0.13 at 2 h after intravenous injection, with the subsequent gradual decline. This value is higher than that of commercially available ^99mTc-ciprofloxacin. The abscess to normal muscle ratio shows that ^99mTc-clarithromycin can be successfully used for infection imaging, allowing differentiation between bacterial infection and sterile inflammation.     

Study of Magnetic Entropy Change in Nd<Subscript>0.67</Subscript>Ba<Subscript>0.33</Subscript>Mn<Subscript>0.98</Subscript>Fe<Subscript>0.02</Subscript>O<Subscript>3</Subscript> by Means of Theoretical Models

Magnetic entropy change (?ΔS _M ) of Nd_0.67 Ba_0.33Mn_0.98Fe_0.02O₃ perovskite have been analyzed by means of theoretical models. An excellent agreement has been found between the (ΔS_M) values estimated by Landau theory and those obtained using the classical Maxwell relation. In order to estimate the spontaneous magnetization M _{s pont}(T), we used the mean-field theory to analyses the (ΔS_M) vs. M ² data. The obtained M _{s pont}(T) values are in good agreement with those found from the classical extrapolation from the Arrott plots(H/M vs. M ²), confirming that the magnetic entropy is a valid approach to estimate the spontaneous magnetization in our system. At a relatively low magnetic field, a phenomenological model has been used to estimate the values of the magnetic entropy change. The results are in good agreement with those obtained from the experimental data using Maxwell relation.     

New NaSrPO<Subscript>4</Subscript>:Sm<Superscript>3+</Superscript> phosphor as orange-red emitting material

Sm³⁺-activated NaSrPO₄ phosphors could be efficiently excited at 403 nm, and exhibited a bright red emission mainly including four wavelength peaks of 565, 600, 646 and 710 nm. The highest emission intensity was found for NaSr _1?x PO₄: xSm³⁺ with a composition of x = 0.007. Concentration quenching was observed as the composition of x exceeds 0.007. The decay time values of NaSr_1?x PO ₄ : xSm³⁺ phosphors range from around 2.55 to 3.49 ms. NaSr_1?x PO₄: xSm³⁺ phosphor shows a higher thermally stable luminescence and its thermal quenching temperature T ₅₀ was found to be 350°C, which is higher than that of commercial YAG:Ce³⁺ phosphor and ZnS:(Al, Ag) phosphor. Because NaSr_1?x PO₄: xSm³⁺ phosphor features a high colour-rendering index and chemical stability, it is potentially useful as a new scintillation material for white light-emitting diodes.     

Influence of Nd doping on microwave dielectric properties of SrTiO<Subscript>3</Subscript> ceramics

Sr_1?x Nd _x TiO₃ (x?=?0.08–0.14) ceramics were prepared by conventional solid-state methods. The analysis of crystal structure suggested Sr_1?x Nd _x TiO₃ ceramics appeared to form tetragonal perovskite structure. The relationship between charge compensation mechanism, microstructure feature and microwave dielectric properties were investigated. Trivalent Nd³⁺ substituting Sr²⁺ could effectively decrease oxygen vacancies. This reduction and relative density were critical to improve Q?×?f values of Sr_1?x Nd _x TiO₃ ceramics. For ε _r values, incorporation of Nd could restrain the rattling of Ti⁴⁺ cations and led to the reduction of dielectric constant. The τ _f values were strongly influenced by tilting of oxygen octahedral. The τ _f values decreased from 883 to 650 ppm/°C with x increasing from 0.08 to 0.14. A better microwave dielectric property was achieved for composition Sr_0.92Nd_0.08TiO₃ at 1460 °C: ε _r ?=?160, Q?×?f?=?6602 GHz, τ _f ?=?883 ppm/°C.     

Inducement of Itinerant Electron Transport in Charge-Ordered Pr<Subscript>0.6</Subscript>Ca<Subscript>0.4</Subscript>MnO<Subscript>3</Subscript> by Ba Doping

The effects of Ba ²⁺ doping on the electrical and magnetic properties of charge-ordered Pr_0.6Ca_0.4MnO₃ were investigated through electrical resistivity and AC susceptibility measurements. X-ray diffraction data analysis showed an increase in unit cell volume with increasing Ba ²⁺ content indicating the possibility of substituting Ba ²⁺ for the Ca-site. Electrical resistivity measurements showed insulating behavior and a resistivity anomaly at around 220 K. This anomaly is attributed to the existence of charge ordering transition temperature, \(T^{\mathrm {R}}_{\text {CO}}\) for the x = 0 sample. The Ba-substituted samples exhibited metallic to insulator transition (MI) behavior, with transition temperature, T _MI, increasing from ～98 K (x = 0.1) to ～122 K (x = 0.3). AC susceptibility measurements showed ferromagnetic to paramagnetic (FM-PM) transition for Ba-substituted samples with FM-PM transition temperature, T _c, increasing from ～121 K (x = 0.1) to ～170 K (x = 0.3), while for x = 0, an antiferromagnetic to paramagnetic transition behavior with transition temperature, T _N, ～170 K was observed. In addition, inverse susceptibility versus T plot showed a deviation from the Curie–Weiss behavior above T _c, indicating the existence of the Griffiths phase with deviation temperature, T _G, increasing from 160 K (x = 0.1) to 206 K (x = 0.3). Magnetoresistance, MR, behavior indicates intrinsic MR mechanism for x = 0.1 which changed to extrinsic MR for x > 0.2 as a result of Ba substitution. The weakening of charge ordering and inducement of ferromagnetic metallic (FMM) state as well as increase in both T _c and T _MI are suggested to be related to the increase of tolerance factor, τ, and increase of e _g ?electron bandwidth as average ionic radius at A-site, <r _A> increased with Ba substitution. The substitution may have reduced MnO₆ octahedral distortion and changed the Mn–O–Mn angle which, in turn, promotes itinerancy of charge carrier and enhanced double exchange mechanism. On the other hand, increase in A-site disorder, which is indicated by the increase in σ ² is suggested to be responsible for the widening of the difference between T _c and T _MI.     

Phenomenological Model of Magnetocaloric Effect in La<Subscript>0.7</Subscript>Ca<Subscript>0.2</Subscript>Ba<Subscript>0.1</Subscript>MnO<Subscript>3</Subscript> Manganite Around Room Temperature

In this work, we studied in detail the magnetic and magnetocaloric properties of the La_0.7Ca_0.2Ba_0.1MnO₃ compound according to the phenomenological model. Based on this model, the magnetocaloric parameters such as the maximum of the magnetic entropy change ΔS _M and the relative cooling power (RCP) have been determined from the magnetization data as a function of temperature at several magnetic fields. The theoretical predictions are found to closely agree with the experimental measurements, which make our sample a suitable candidate for refrigeration near room temperature. In addition, field dependences of \({{\Delta } S}_{\mathrm {M}}^{\max }\) and RCP can be expressed by the power laws \({\Delta S}_{\mathrm {M}}^{\max }\approx a\)(μ ₀ H) ⁿ and RCP ≈b(μ ₀ H) ^m , where a and b are coefficients and n and m are the field exponents, respectively. Moreover, phenomenological universal curves of entropy change confirm the second-order phase transition.     

High-temperature crystal chemistry of Na<Subscript>6</Subscript>(UO<Subscript>2</Subscript>)<Subscript>2</Subscript>O(MoO<Subscript>4</Subscript>)<Subscript>4</Subscript>

Thermal deformations of Na₆(UO₂)₂O(MoO₄)₄ were studied by high-temperature powder X-ray diffraction. The compound crystallizes in the triclinic system, space group Р\(\bar 1\), a = 7.636(7), b = 8.163(6), c = 8.746(4) Å, α = 72.32(9)°, β = 79.36(4)°, γ = 65.79(5)°, V = 472.74(4) ų. It is stable in the temperature interval 20–700°С. The thermal expansion coefficients (TECs) are α₁₁ = 25.5 × 10^–6, α₂₂ = 7.8 × 10^–6, and α₃₃ = 1.1 × 10^–6 (°C)^–1. The orientation of the TEC pattern relative to the crystallographic axes is a₃₃^Z = 45°, a₃₃^X = 122°, a₂₂^Z = 59°, and a₂₂^X = 66°. The anisotropy of the thermal expansion is due to specific features of the crystal structure of the compound.     

Effects of Ge<Superscript>4+</Superscript> acceptor dopant on sintering and electrical properties of (K<Subscript>0.5</Subscript>Na<Subscript>0.5</Subscript>)NbO<Subscript>3</Subscript> lead-free piezoceramics

Lead-free (K_0.5Na_0.5)(Nb_1-xGe _x )O₃ (KNN-xGe, where x = 0-0.01) piezoelectric ceramics were prepared by conventional ceramic processing. The effects of Ge⁴⁺ cation doping on the phase compositions, microstructure and electrical properties of KNN ceramics were studied. SEM images show that Ge⁴⁺ cation doping improved the sintering and promoted the grain growth of the KNN ceramics. Dielectric and ferroelectric measurements proved that Ge⁴⁺ cations substituted Nb⁵⁺ ions as acceptors, and the Curie temperature (T_C) shows an almost linear decrease with increasing the Ge⁴⁺ content. Combining this result with microstructure observations and electrical measurements, it is concluded that the optimal sintering temperature for KNN-xGe ceramics was 1020°C. Ge⁴⁺ doping less than 0.4 mol.%can improve the compositional homogeneity and piezoelectric properties of KNN ceramics. The KNN-xGe ceramics with x = 0.2% exhibited the best piezoelectric properties: piezoelectric constant d₃₃ = 120 pC/N, planar electromechanical coupling coefficient k_p = 34.7%, mechanical quality factor Q_m = 130, and tanδ = 3.6%.