Narrow Results

We conducted a study on Mn doping in 67Pb (Mg${}_{1∕3}$Nb${}_{2∕3}$)O₃-33PbTiO₃(67PMN-33PT), which is a ferroelectric material exhibiting a morphotropic phase boundary (MPB). The samples were doped with MnO₂ at mass ratios ranging from 0.5 to 5.0wt.% and subsequently sintered at temperatures ranging from 1200 to $1260^{\circ }$C. Experimental analysis of electrical properties was performed within the temperature range of $-80$–$200^{\circ }$C. Electron paramagnetic resonance (EPR) testing was conducted on these samples to investigate Mn solubility in PMN-PT ceramics and their existence in different valence states. The results indicate that at a doping ratio of 0.5wt.% and sintering temperature of 1220–1240^∘C, Mn ions achieved a homogeneous dispersion within the crystal lattice, leading to the enhanced electromechanical $Q_m$ factor (510) and the reduced dielectric loss tan $\delta$ to minimum (0.30%) compared to the no doping Mn, however, as the Mn ions dopant content increase higher than 1.0wt.% and sintering temperatures 1200–1260^∘, the unexpected results have been observed that both $Q_m$ and tan $\delta$ are enhanced to about 1200, 0.87 up to 1.5wt.% MnO₂, and then, $Q_m$ decreases to 510, but tan $\delta$ increases to 3.78% for 5 wt.% MnO₂. The machinal $Q_m$ and dielectric loss can be understood by the (Mn-Vo) defect dipoles in lattice, domain wall and grain-bounary, together with the increasing of the MnO₂, Mn₂O₃ or their mixed phase of Mn₃O₄ in the grain boundary.

Pure ZnO and Zn_1-xMn_xO (x=0.02 and 0.06) nanopowders have been synthesized by sol–gel technique at low temperatures. XRD results indicated that the crystal structure is hexagonal and there is no secondary phase. The compositional characterization of Mn-doped samples was investigated by EDX spectra. The size and morphology of nanoparticles were obtained by SEM and TEM images. Optical constants such as refractive index and extinction coefficient were evaluated from transmittance spectrum in UV region. The optical band gap energy showed a red-shift from 3.22 eV to 3.14 eV for pure and Zn_0.94Mn_0.06O, respectively. The Curie temperature of Mn-doped ZnO samples were determined and at room temperature no ferromagnetism state was observed.

A series of BiFeO₃ and BiFe${}_{1-x}$Mn${}_x$O₃ (x = 0, 0.02, 0.04, 0.06, 0.08, 0.10) were synthesized by a hydrothermal method. The samples were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy (EDS) and UV–Vis diffuse reflectance spectroscopy, and their photocatalytic activity was studied by photocatalytic degradation of methylene blue in aqueous solution under visible light irradiation. The band gap of BiFeO₃ was significantly decreased from 2.26 eV to 1.90 eV with the doping of Mn. Furthermore, the 6% Mn-doped BiFeO₃ photocatalyst exhibited the best activity with a degradation rate of 94% after irradiation for 100 min. The enhanced photocatalytic activity with Mn doping could be attributed to the enhanced optical absorption, increment of surface reactive sites and reduction of electron–hole recombination. Our results may be conducive to design more efficient photocatalysts responsive to visible light among narrow band gap semiconductors.

Ba(Zr_0.2Ti_0.8)O₃ (BZT) and 2 mol% Mn additional doped BZT (Mn-BZT) thin films were deposited by pulsed laser deposition technique under the same growth conditions on LaAlO₃ substrates with the bottom electrodes of LaNiO₃. The microstructure of the films was characterized by X-ray diffraction (XRD) in the mode of θ–2θ scan and Φ-scan. The results indicated that BZT film was (001)-oriented_with an in-plane relationship of BZT[100]//LNO[100]//LAO[100]. The Mn-BZT film exhibited higher dielectric constant of 225 at zero electric field, larger dielectric tunability of 59.4%, and lower dielectric loss of 1.8% under an applied electric field of 720 kV/cm. The figure of merit for BZT thin film increased from 19.8 to 33 by Mn doping. The enhanced dielectric behavior by Mn doping could be mainly attributed to the decrease of oxygen vacancies and the reorientation of the dipolar defect complex of .

A sol–gel method was used to synthesize TiO₂ nanoparticles doped with varying amounts of Mn. The physico-chemical properties of the synthesized nanoparticles were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and diffuse reflection spectroscopy (DRS). The XRD results indicated that the anatase phase was the major phase of TiO₂, while a minor rutile phase was observed in the Mn-doped TiO₂ 0.2 wt.% and 0.3 wt.% samples. The TEM analysis showed that the Mn atoms existed in different oxidation states, including Mn${}^{2+}$, Mn${}^{3+}$, Mn${}^{4+}$ and Mn${}^{7+}$, and that the nanoparticles had a spherical-like morphology with a size ranging from 10nm. The narrowest band gap of 2.80eV was observed in the Mn-doped TiO₂ 0.2 wt.% sample. The photocatalytic activity of the synthesized nanoparticles was evaluated for methylene blue (MB) photodegradation and Escherichia coli (E. coli) photokilling under visible light irradiation. The MB degradation efficiency was found to be the highest in the Mn-doped TiO₂ 0.2 wt.% sample, with a removal efficiency of 96% and a degradation rate constant of 0.08 1/min. The degradation efficiency decreased in the following order: Mn-doped TiO₂ 0.1 wt.%, 0.3 wt.% and undoped TiO₂. Similarly, complete E. coli photokilling was achieved only in the Mn-doped TiO₂ 0.2 wt.% sample, while some residual E. coli was observed in the other doping nanoparticles and undoped TiO₂. In summary, the results suggest that Mn doping significantly improved the photocatalytic activity of TiO₂ nanoparticles, and the Mn-doped TiO₂ 0.2 wt.% sample exhibited the highest efficiency in both MB photodegradation and E. coli photokilling under visible light irradiation.

${\mathrm{\text{La}}}_{0.8}{\mathrm{\text{Sr}}}_{0.2}{\mathrm{\text{Fe}}}_{1-x}{\mathrm{\text{Mn}}}_x{\mathrm{\text{O}}}_3$ ($x=0.0$, 0.1, 0.3 and 0.5) series samples were prepared by sol–gel method and characterized by powder X-ray diffractometer (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and Mössbauer spectroscopy. The effects of Mn doping on the microstructure, morphology and electronic structure of La–Sr ferrite were investigated. The XRD results show that all samples are single phase and have orthorhombic structures with Pbnm space group. The surface morphology and composition of chemical elements of the samples were analyzed by SEM and EDS, and the experimental values were consistent with the expected values. The sample was tested by ${}^{57}$Fe Mössbauer spectroscopy at room temperature, and the results showed that the percentage of doublet increased gradually with the increase of Mn ion doping ratio, and at $x=0.5$, all the sextet disappeared and only the doublet existed. According to the analysis, it can be seen that the prepared series of samples underwent a transition from antiferromagnetic to paramagnetic.

BiFe_1-xMn_xO₃ (BFMO) films (x = 0, 0.05, 0.1) were grown on (001) LaAlO₃ (LAO) substrates to demonstrate the role of chemical pressure on the lattice structure and magnetic behaviors of compressively-strained BiFeO₃ (BFO) films. The structural analyses indicated that the substitution of Jahn–Teller active ion Mn at Fe site tuned the ferroelectric distortion and antiferrodistortive (AFD) rotation in BFO lattice, thus weakened the tetragonal-like (T-like) phase originated from the large substrate clamping. The phase transition mechanism was discussed to reveal the competition between inner lattice distortion and external stress in BFO films. Clear domain variants change from (T-like) phase to rhombohedral-like (R-like) phase provided further evidence for the structure alteration. Meanwhile the gradual relaxation in total lattice strain of BFMO films with increasing x reduced the magnetism contribution from the strong spin and lattice coupling.