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Photocatalytic, magnetic and antimicrobial properties of barium zirconate (BaZrO3) perovskite green synthesized using Plectranthus amboinicus (P. amboinicus) and Ocimum sanctum (O. sanctum) leaf extracts has been summarized here. Confirmation of cubic structure with (1 1 0) preferential growth has been arrived from the XRD studies. The occupancy of magnetic metal ions such as Cu2+, Ni2+, Mn2+ and Co2+ on the octahedral A and B sites makes P. amboinicus and O. sanctum leaf extract–mediated BaZrO3 paramagnetic and ferromagnetic, respectively. Antimicrobial studies performed against Pseudomonas aeruginosa bacteria justifies that the green synthesized samples exhibited good inhibition on its growth. Photocatalytic activity of the green synthesized BaZrO3 nanoparticles was explored by Congo red dye degradation under ultra-violet illumination. Increased degradation efficiency and photostability were realised for O. sanctum leaf extract–mediated BaZrO3. The obtained results infer that the O. sanctum leaf extract–mediated BaZrO3 perovskite is well suited for soft magnetic materials, biological and catalytic applications. [ABSTRACT FROM AUTHOR]

We report the synthesis and magnetic properties of polycrystalline Sr2Cu(Re0.69-xWxCa0.31)O6 samples with x=0, 0.1, 0.2, 0.3, 0.4, 0.5, and 0.6, which were prepared by high-pressure high-temperature synthesis technique. These phases had ordered cubic perovskite structures. The pristine compound (x=0) underwent a ferromagnetic (ferrimagnetic) transition with TC∼460 K. The ferromagnetism was suppressed by the W substitution and disappears almost completely for x=0.6. Mechanism of the suppression of the magnetism is discussed assuming a localized electron system. [ABSTRACT FROM AUTHOR]

The physical properties of high-pressure synthesized polycrystalline Cu(ReMoCa)SrO samples are reported in this article to attract the scientific community. The present system undergoes a structural phase transition from cubic symmetry (for x=0, 0.1) to tetragonal for 0.2≤ x≤0.4 and again cubic perovskite structure for x=0.5 and 0.6. The pristine compound ( x=0) undergoes a ferromagnetic (ferrimagnetic) transition with high T∼460 K. Neither the Curie temperature nor the effective magnetic moment is enhanced upon Mo substitution. The mechanism of the suppression of ferromagnetism in the present system is discussed assuming a localized electron system which is reminiscent of W substitution (Balamurugan et al. in J. Appl. Phys. 101:09N501, ). The temperature dependence of electrical resistivity, ρ decreases with x=0-0.4 and then increases for x=0.5 and 0.6. Though the suppression of ferromagnetism in the present system is similar to W-substitution, interestingly the former one (Mo) shows different results on structural and transport electrical properties which urge for further studies. The interesting aspect of the present work is for x=0.6, the specific heat data shows significant electronic contribution, whereas the resistivity measurement reveals insulating behavior. [ABSTRACT FROM AUTHOR]

In order to check the solubility of Zn in the (SrZn)CoO perovskite structure and their research findings, several polycrystalline samples have been prepared under wide extreme synthesis conditions at 6 GPa/1300-1650 °C. While 0.05≤ x≤0.3 compositions revealed single phased cubic structure materials, x>0.3 showed multi-phased materials for (SrZn)CoO system. Like other substituted perovskite cobalt oxide systems (Ca, Y, Ho and Ce), the transport properties of the present materials show rather sizable changes with respect to ' x', although there are insignificant variations in lattice parameter and in Curie temperature, T. All the present samples show soft ferromagnetism with T in the range of 272-285 K for 0.05≤ x≤0.3. The effective paramagnetic moment, P determined from the paramagnetic region decreases upon the substitution of Zn for Sr-site. These P (3.3-2.8 μ/Co) values for 0.05≤ x≤0.3 compositions seem to suggest that the Co lie in intermediate spin (IS) state for the present (SrZn)CoO series, although they are slightly smaller than those expected for IS-Co; P=3.87 μ/Co. The electrical resistivity is found to increase with increase of ' x' for the investigated samples. The temperature and field dependence of both positive and negative magnetoresistance (MR) are noted for the Zn substituted samples. About 5% of -MR is observed for x=0.05 sample around the transition temperature (280 K) under the field strength difference, Δ H=90 kOe. The present research findings are compared with our previous results on different perovskite cobalt oxides. [ABSTRACT FROM AUTHOR]

In this article, the magneto-transport features of 57Fe isotope (1%) doped SrCoO3 (referred to as SrCo0.99 57Fe0.01O3) perovskite compound have been investigated. The compound crystallized in cubic symmetry undergoes ferromagnetic transition around ∼270 K. The isothermal magnetization data collected at low temperature (1.8 K) indicates a characteristic of soft ferromagnet with saturation moment, Ms∼1.81 μB/Co. Interestingly, the electrical resistivity, ρ( T), measurements indicate semiconducting properties while metallic nature is seen for the pristine compound. The SrCo0.99 57Fe0.01O3 sample shows temperature and field dependence of magnetoresistance, MR, around 1.5%, which is rather smaller than of the pristine perovskite. The second part of the present work reports the attempt to dope Cd on Sr-site in the perovskite structure, Sr1− xCd xCoO3, under extreme conditions. A minimum amount of about x=0.05, 0.1 is tested for solid solution in the Sr1− xCd xCoO3 structure. However, the structural data indicate that Cd is not fully doped in the matrix for x=0.05, 0.1 samples; some of the CdO is intact as an impurity and it did not show major impact on the physical properties of the samples. The ρ( T) data reveal metallic nature for both x=0.05 and 0.1 samples with relatively low resistivity at low temperature regions, and they exhibit − MR ∼4% around ∼250 K. For x=0.05 the molar magnetic susceptibility of the sample shows ferromagnetic transition at Tc=244 K, whereas x=0.1 sample exhibits ferromagnetism at Tc=264 K. The effective Bohr magnetron parameter, peff, determined for x=0.05 and 0.1 samples is found to be 3.10 μB/Co and 3.25 μB/Co, respectively, and these data suggest intermediate spin state for Co4+ ion for both the samples. The M( H) data for both the samples reveal soft ferromagnetism. The Ms of x=0.05 reaches 1.9 μB/Co and of x=0.1 reaches 1.86 μB/Co at 1.8 K and 70 kOe conditions. [ABSTRACT FROM AUTHOR]

In this brief article, structural, magnetization studies of oxygen deficient perovskite cobalt oxides CoSrO3− δ synthesized in two different ways are reported. The structural refinements (JANA2006) of X-ray powder diffraction data indicate that the sample prepared under ambient pressure ( stage-1) shows a hexagonal structure with P63/ mmc (194) as a possible space group. The stage-1 sample subsequently sintered at 1450 °C for 1–2 h under high-pressure 6 GPa conditions ( stage-2) crystallizes in tetragonal symmetry with I4/ mcm (140) space group having a=5.444(7) Å and c=7.68(2) Å. While the stage-1 sample exhibits a paramagnetic nature in the magnetic susceptibility, M( T), measurements, interestingly the sample annealed under high-pressure conditions shows ferromagnetism in the magnetic susceptibility, M( T) and field dependence magnetization, M( H) measurements. The high-pressure annealed sample shows hysteresis opening with a quite large coercive field of 7.3 kOe at 1.8 K. The temperature dependence of the inverse molar susceptibility curves exhibits linear behavior in the high-temperature regime and could be fitted to the Curie–Weiss expression, χ( T)= C/( T− θW). The experimental values of θW and peff obtained from the linear region of the inverse molar magnetic susceptibility curves are found to be: −210.7(5) K and 2.38(2) μB/Co for stage-1 and 260.2(7) K and 1.87(3) μB/Co for stage-2 samples, respectively. A negative sign of θW indicates rather strong antiferromagnetic correlations in the stage-1 sample. Apart from these results, the structural parameters reported by various groups for the strontium-based perovskite cobalt oxides are also presented in the form of literature collections. [ABSTRACT FROM AUTHOR]

Abstract: Polycrystalline perovskite cobalt oxides Sr1– xRx CoO3 (R=Y and Ho; ) were prepared by high-pressure/high-temperature technique. X-ray powder patterns of the Y-system indicated cubic perovskite form for , and orthorhombic perovskite form for and 1.0, while coexisting of the two phases for . The cubic perovskite samples had metallic electric resistivities while the orthorhombic ones with semiconducting or insulating nature. The parent compound SrCoO3 showed a ferromagnetic transition at 266K. With the Y substitution, the transition temperature increased slightly to ∼275K at , then decreased rapidly to ∼60K for . The YCoO3 () sample showed non-magnetic behavior. The Ho-substituted system showed quite similar structural, transport and magnetic properties to those of the Y-system. [Copyright &y& Elsevier]

Abstract: Polycrystalline perovskite cobalt oxides (Sr1– x Ca x )CoO3 (0⩽x⩽0.8) were synthesized under high pressure (6GPa) and high temperature (1200–1300 °C) conditions. Powder X-ray diffraction data confirmed that they have cubic perovskite structures. The end member of the solid solution, SrCoO3, exhibited a ferromagnetic transition with Curie temperature of and metallic electric conductivity. With increasing the Ca content , increased slightly to 286K at then decreased rapidly to 148K for . The origin of the ferromagnetism is discussed in relation to the spin state of the Co4+ ions. The present system showed a relatively large (∼5.5%) negative magnetoresistance for or 0.2 in the vicinity of T c. [Copyright &y& Elsevier]

• BaZrO 3 perovskite is green synthesized using M. oleifera leaf extract. • The green synthesized BaZrO 3 exhibited excellent antimicrobial activity. • A maximum degradation efficiency of 84.1% was realized by the green synthesized catalyst. • Z-scan studies confirmed that the defocusing nature of the green synthesized BaZrO 3. In this paper, BaZrO 3 was chemically synthesized using liquid NH 3 as precipitating agent and green synthesized using Moringa oleifera (M. oleifera) leaf extract without the addition of liquid NH 3. X-ray diffractograms confirmed the cubic nature of the samples with. (1 1 0) preferential growth. XPS studies ascertain the existence of Ba, Zr and O in the green synthesized sample. Decreased band gap was observed for the green synthesized sample. Ba-O stretching vibrations were observed respectively at 480 and 487 cm−1 for the chemically synthesized and green synthesized samples. The green synthesized BaZrO 3 exhibits better degradation efficiency of 84.1% after 90 min against CR dye. The green synthesized BaZrO 3 nanoparticles exhibited excellent antimicrobial activity against E. coli and A. terreus. The third order nonlinear absorption coefficient and susceptibility values of the green synthesized BaZrO 3 were found to be equal to 3.05 × 10−6 cm/W and 4.67 × 10−8 esu, respectively. [ABSTRACT FROM AUTHOR]