Increase Of Mn4 Research Articles

Electrical transport properties of topographically demorphed films of La1-xBaxMnO3 grown on (00l)-oriented LaAlO3 substrate via spin-coating method

Herein, the crystal structure, valence, and electrical transport properties of La1-xBaxMnO3 films were examined by preparing La1-xBaxMnO3 films with varying Ba content (x = 0.22, 0.24, 0.26, 0.28) on LaAlO3 substrates using the sol-gel spin coating technique. The La1-xBaxMnO3 films prepared in the study exhibit topographically demorphed and non-dense characteristics in the microstructure, which is mainly caused by the Volmer-Weber growth mode of the films and the volatilization of organic matter during the sol-gel sintering process for films preparation. The increase of Ba doping leads to MnO6 deformation, decrease in grain boundary scattering, increase in Mn4+ ion content, and enhancement of both the double exchange mechanism and the Jahn-Teller effect. The four-probe results showed that the peak resistivity of the films decreased significantly with the increase in Ba2+ doping, and the metal-insulator transition temperature (Tp) shifted to higher temperatures. Peak temperature coefficient of resistivity (TCR) corresponding temperature (Tk) increased from 283.05 K (x = 0.22) to 309.31 K (x = 0.28), which was consistent with the trend of Tp; the peak value of TCR decreased with the increase of Ba doping. When x = 0.24, the Tk of the La1-xBaxMnO3 films reach room temperature (294.25 K) with TCR = 9.01 % K−1. In conclusion, the electrical properties of La1-xBaxMnO3 can be optimized by varying the amount of Ba doping to obtain La1-xBaxMnO3 films with room-temperature Tk and higher TCR values, providing reasonable data support and theoretical explanation for the Ba doping mechanism.

Cation Occupation Engineering Realizes Valence Modulation of Manganese-Activated ZnGa2O4.

Herein, a series of Mn-activated ZnGa2O4 (ZGO) phosphors have been developed for multifunctional applications. The characteristic green and red emission at 503 and 668 nm of Mn-activated ZGO phosphors can be observed under excitation of 247 and 375 nm, respectively, attributed to the partial oxidation of Mn2+ ions resulting in the coexistence of Mn2+ and Mn4+ ions in the host lattice. The valence modulation of Mn content not only realizes the adjustment of red and green luminescence intensity but also achieves the management of persistent luminescence time and thermo-luminescence time. Further, the codoping of Mg2+ could transform the position occupancy preference of Mn and effectively facilitate the conversion of Mn2+ to Mn4+, leading to the regulation of the valence state of manganese ions. Surprisingly, the existence of Mg2+ ions broadens the emission band of Mn4+ and enhances the photoluminescence intensity to 3.8 times, which can be ascribed to the weakened crystal field leading to the downward shift of the 4T2 energy level and the increase of Mn4+ concentration. For this valence modulation behavior, two different hypotheses about the occupancy of Mg2+ have been proposed to explain the corresponding phenomenon. Finally, the potential applications of the synthesized phosphors have been explored in advanced anticounterfeiting strategies, information storage, and plant lighting field.

Synergistic effect to unlock the activity and stability for oxygen evolution reaction in spinel LiMn2O4 via d-block metal substitution

An effective strategy using d-block metal hybridization was proposed to induce electronic interaction and promote the synergistic effect, aiming to enhance the OER performance of cost-effective spinel LiMn2O4. Indeed, we deployed a series of LiNixMn2-xO4 catalysts substituted with Ni, yielding the increase of Mn valence states from Mn3.5+ to Mn4+. The LiNi0.5Mn1.5O4 catalyst achieved an excellent OER performance in alkaline media, with an overpotential reduction more than 320 mV at 10 mA cm−2 compared to the unsubstituted LiMn2O4, as well as the electrochemical stability. It was shown to be superior to the most reported Mn-based oxides OER electrocatalysts. Theoretical calculations demonstrated that Ni doped holes in the Mn site, leading to an increase in Mn4+, and that the shared covalent network of Ni 3d-O 2p-Mn 3d optimized an easier desorption of intermediates. These results pave a new example for modulating the chemisorption strength, thus enabling activating the activity and stability of OER process for cost-effective electrocatalysts based on spinel Mn oxides.

Effect of A-site rare-earth ions on structure and magnetic properties of novel (Ln0.2Gd0.2La0.2Nd0.2Sm0.2)MnO3 (Ln = Eu, Ho, Yb) high-entropy perovskite ceramics

Single-phase high-entropy perovskite ceramics (Ln0.2Gd0.2La0.2Nd0.2Sm0.2)MnO3 (Ln-GLNSMO HEPCs) have been synthesized using solid-state reactions. The effect of A-site rare-earth ions (Ln = Eu, Ho, Yb) on the structure and magnetic properties was systematically investigated. The results show that all samples are orthorhombic phases (with a space group of Pbnm) and exhibit a strong crystallization trend sintered at 1300 °C for 16 h. All the HEPCs are composed of irregular spherical particles with smooth surfaces and show obvious hysteresis effects at T = 5 K. The changing Mn–O bond distance, Mn–O–Mn bond angle and the increase of Mn4+ ion concentration enhance the double exchange effect of Mn3+-O2--Mn4+, leading to different magnetic interactions. The residual magnetization Mr (coercivity Hc) of the samples is significantly enhanced, which is increasing from 0.13 emu/g (16.34 Oe) to 3.17 emu/g (97.07 Oe) due to the increase of configuration entropy, lattice distortion and the double exchange effect (DE). In addition, there is a strong relationship between the magnetic properties and the average radius of the A-site ions, in which Ho-GLNSMO HEPCs have a high Ms magnetism. This work is a valuable reference for the magnetic regulation of high-entropy ceramics based on rare-earth and entropy-stabilized perovskite types.

Effect of Sm doping on structure, dielectric properties and microwave absorption performance of SrMnO3

In this work, Sr1-xSmxMnO3(x = 0,0.5) powders were prepared by solid-state reaction method. The effects of Sm doping on structure, electromagnetic properties and microwave absorption performance of SrMnO3 were systematically investigated by experimental characterizations and first-principles calculations. It is found that the doping of Sm transforms the hexagonal structure P63/mmc of SrMnO3(SMO) into an orthorhombic phase Pnma of Sr0.5Sm0.5MnO3 (SSMO) at room temperature. Sm doping and the increase of Mn3+ content induce the lattice distortion, resulting in octahedral torsion and the Mn–O–Mn bond angle towards 180°. Furthermore, doping introduces additional oxygen vacancies and defects in SMO, significantly enhancing various polarizations within the system. As a result, there is a substantial improvement in the microwave absorption capability of the doped sample. Compared to undoped SMO, SSMO performs excellent microwave absorbing properties in the higher frequency band and the value of reflection loss has increased by 29.47 dB at the optimal matching thickness.

A high rate and stability cathode material for half/full sodium-ion batteries: Nb-substituted NaNi1/3Mn1/3−xFe1/3NbxO2 layered oxides

O3 layered oxide cathode materials have infinite development potential in sodium ion batteries (SIBs), but complex phase transitions usually result in poor rate capacity. In this study, NaNi1/3Mn1/3−xFe1/3NbxO2 (NFM-Nb x, x = 0, 0.01, 0.02) precursor were synthesized through ball-milling spray drying method. The structure morphology characterization confirmed that Nb was successfully doped into the material and replaced part of Mn in the transition metal. The chemical valence analysis shows that Nb doping promoted the reduction of Mn4+ to Mn3+, and the increase of Mn3+ improved the ionic conductivity. NFM-Nb 0.01 significantly improved long cycle stability and rate capacity, the capacity of NFM-Nb 0.01 at 1 C and 5 C were 125.4 and 115.5 mAh g−1, respectively, and the corresponding cycle retention rate maintained 83. 81% and 83.12%. NFM-Nb 0.01 has a 25.06% higher capacity retention rate than NFM after 100 cycles at 1 C in the voltage range 2–4.3 V. For full-cell, NFM-Nb 0.01//HC delivered the capacity of 79.4 mAh g−1 at 10 C after 200 cycles and kept 71.16% cycle retention. The results of ex-situ XRD further investigated Nb-substitution enhanced the structure recoverability of cathode materials. The failure analysis result showed that Nb substitution is beneficial to stabilize the layered structure of materials, improve the cycling performance under high voltage.

Site occupancy strategy for emission tunable K3HF2W1-xOF6:xMn4+ nanophosphor via ions exchange

A novel uniformly ellipsoidal K3HF2W1-xOF6:xMn4+ nanophosphor were demonstrated by ion exchange method without K2MnF6. The samples had wide excitation range from ultraviolet to visible light and tunable emission spectra from green to red were obtained which can be regulated by the emitting spectra of K3HF2WOF6 host and Mn4+. Energy transfer efficiency from [WOF6]2− to Mn4+ were improved with the increase of Mn4+. The peak position of thermal stability spectra of K3HF2WOF6 were blueshifted while Mn4+ doped samples undergoes a redshift. The crystal field strength and the Racah parameters were estimated and luminescence mechanism was explained by the Tanabe–Sugano energy level diagram of the Mn4+. Microsecond fluorescence lifetime indicates it advantages in fast react displays to avoid ghost images. The results indicate that K3HF2W1-xOF6:xMn4+ nanophosphor has potential application in display, converting phosphors for UV and blue LED and indoor plant supplyment light.

Synergistic effect of Mn3+ and oxygen vacancy on the bifunctional oxygen electrocatalytic performance of MnOX/CNTs composites

Manganese oxides have been proved to be a promising low-cost electrocatalyst for oxygen reduction reaction (ORR) and a critical step in systems of zinc-air batteries, however, which is limited by the poor electrical conductivity. In this paper, we introduce carbon nanotubes (CNTs) as conductive supports to further prepare manganese oxide/CNTs composites with bifunctional electrocatalytic activity by the incorporation of redox and calcination two-step approach. Meanwhile, the effects of mass ratio, calcination temperature and oxidation degree on the oxygen reduction reaction (ORR) activity of the composites were studied. The electrocatalytic results showed that the MnO2/CNTs exhibited better electrocatalytic activity than that of manganese dioxide (MnO2) and CNTs when the mass ratio of CNTs to MnO2 was 60%. After calcination at 400 °C and reduction treatment of sulfur (S) to adjust the surface oxygen vacancy concentration and Mn3+ content, the ORR and oxygen evolution reaction (OER) bifunctional catalytic activity of the obtained MnOX/CNTs-400 was significantly enhanced. The ORR half-wave potential (E1/2) and bifunctional potential difference (ΔEOER-ORR) between the ORR half-wave potential and OER potential at 10 mA cm−2 were 0.77 V and 0.92 V, respectively, due to the introducing of highly conductive CNTs, increase of Mn3+ content and oxygen vacancy concentration. Furthermore, the composite also exhibits higher methanol tolerance and long-term stability than the commercial Pt/C catalyst, which provided a class of highly efficient ORR/OER bifunctional electrocatalysts with great energy potential.

A Study on the Effects of La/Sm Codoping on the Structural and High Temperature Thermoelectric Properties of n‐Type CaMnO3−δ Perovskite

AbstractOxide thermoelectric ceramics attract extensive research interest due to their excellent thermal stability, non‐toxicity, cost‐effectiveness, and earth‐abundant constituent elements. In the present work, the authors study the effect of lanthanum (La) and samarium (Sm) co‐doping on the structural, microstructural, and thermoelectric properties of CaMnO3 ceramics. The X‐ray diffraction (XRD) studies show an increase in unit cell volume with an increase in Sm concentration. A shift in Raman modes is observed, confirming distortions in MnO6 octahedra with the substitution of rare‐earth elements. The co‐doping strategy leads to a two‐order increment in electrical conductivity and reduction in thermopower as expected due to the increase in Mn3+ and charge carrier concentration. The highest electrical conductivity value attained is ≈200 S cm−1 at around 570 K for La0.025Sm0.1Ca0.875MnO3. The maximum value of thermoelectric power factor achieved is 194 μW m–1 K–2, which is two orders higher than that of the undoped CaMnO3.

MnOx Catalyst with High‐Efficiency Degradation Behavior of Toluene: Effect of Cryptomelane

AbstractA series of MnOx catalysts were prepared by hydrothermal reaction of different pH values, which proved the important influence of preparation conditions on the structure and performance of the catalysts. The results proved that the cryptomelane MnOx catalyst with a pH of 10 (Cat‐2) exhibited the most outstanding performance in catalyzing toluene. The appearance of cryptomelane on Cat‐2 would reduce the chemical valence of Mn, which could increase the content of Mn3+ and the amount of oxygen vacancies. With the increase of Mn3+, the Mn−O bond was broken more easily, and then facilitated the mobility oxygen species, causing the promotion of the catalytic activity. Low‐valence manganese, high‐capacity oxygen vacancies and maximum concentration of lattice oxygen were the most important reasons for the best catalytic activity of Cat‐2. According to the results of in‐situ DRIFT, benzyl, benzaldehyde, benzoic acid were the main intermediate products, which followed the Mars‐van Krevelen mechanism.

Phase composition, morphology, properties and improved catalytic activity of hydrothermally-derived manganese-doped ceria nanoparticles

Manganese-doped ceria nanoparticles were prepared by hydrothermal synthesis and the prepared samples were thermally treated at 500 °C for 2 h. The samples were investigated using x-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), energy-dispersive x-ray spectroscopy (EDS), N2 adsorption and x-ray photoelectron spectroscopy (XPS). XRD revealed that nanocrystalline ceria is the main phase in all samples, while a romanechite-like phase (Na2Mn5O10) appears in the sample doped with 30% of Mn. TEM coupled with EDS exposed the presence of the same phase in the sample doped with 20% Mn. While ceria particles have spherical morphology and particle size ranging from 4.3 to 9.2 nm, the rare crystals of the romanechite-like phase adopt a tubular morphology with a length of at least 1 μm. However, the decrease in the ceria lattice constant and the EDS spectra of the ceria nanoparticles clearly indicate that a substantial amount of manganese entered the ceria crystal lattice. Manganese doping has a beneficial impact on the specific surface area of ceria. XPS measurements reveal a decrease in the Ce3+/Ce3+ + Ce4+ content in the doped samples which is replaced by Mn3+. Moreover, a drastic increase in adsorbed oxygen is observed in the doped samples which is the consequence of the increase in Mn3+ species that promotes oxygen migrations to the surface of the sample. Compared to the pure sample, the doped samples showed significantly higher catalytic activity for the process of toluene oxidation.

Enhanced B-site cation ordering and improved magnetic properties: Role of A-site Bi substitution in La2NiMnO6 double perovskites

The influence of A-site Bi substitution on B-site cation ordering, crystal structure, and magnetic properties of La2-xBixNiMnO6 double perovskites has been studied. Compounds with and without Bi substitution adopt monoclinic crystal structure with the P21/n space group as determined from the Rietveld refinement of x-ray diffraction data. X-ray photoelectron spectroscopy indicated an increase in Mn4+/Mn3+ and Ni2+/Ni3+ ratios in Bi substituted sample, and hence emphasized improved Ni and Mn ordering. This has been well supported by bond length analysis which suggested a compression in<Mn–O>and elongation in<Ni–O>bond lengths. The Bi substituted compound showed a relatively larger moment as compared to the parent sample, which was attributed to the suppression of antisite disorder i.e., enhanced Ni-Mn cation ordering due to Bi substitution. The temperature-dependent dc magnetization studies reveal a ferromagnetic to paramagnetic phase transition, and the Curie temperature has been observed to increases with Bi substitution. The critical exponent analysis around phase transition also confirmed the increase in the critical temperature for the Bi substituted compound. A detailed analysis of the critical behavior has been performed using different models, which suggested a long-range ferromagnetic ordering for both pure and Bi substituted samples.

Enhancement of oxygen permeation flux through the La1.5Sr0.5Ni1-yMnyO4+δ ceramic membranes by manganese doping

The single-phase La1.5Sr0.5Ni1-yMnyO4+δ (y = 0, 0.1, 0.2 and 0.3) dense ceramic membranes of different thickness were fabricated by sintering at 1350 °C in air. The oxygen permeation flux through the La1.5Sr0.5Ni1-yMnyO4+δ membranes slightly decreases at y≤0.2 and increases by more than one order of magnitude in the 0.2 ≤ y ≤ 0.3 range due to a significant increase in the surface oxygen exchange rate. The surface study of La1.5Sr0.5Ni1-yMnyO4+δ by Electron backscatter diffraction technique reveals that manganese doping affects the orientation of crystallites and induces the appearance of planes with higher Miller indices, which are characterized by smaller reticular densities of the 3d-metals. The analysis of the effective paramagnetic moments for La1.5Sr0.5Ni1-yMnyO4+δ shows that manganese doping leads to the formation of mixed Mn3+/Mn4+ oxidation state when y>0.1. As compared to La1.5Sr0.5Ni0.8Mn0.2O4+δ, the significant decrease in surface limitations of the oxygen exchange process at the oxide/gas interface for La1.5Sr0.5Ni0.7Mn0.3O4+δ correlates with the increase in Mn4+ concentration.

Investigation on Anomalous Thermal Quenching of Mn4+ Luminescence in A2XF6:Mn4+

Studying luminescence properties of phosphor materials is not only of scientific interest, but also technological importance. Here, we investigate luminescence intensity as a function of temperature for Mn4+-activated fluoride and oxide phosphors. A recent study suggested that an anomalous increase in Mn4+ luminescence intensity (I PL) with increasing lattice temperature (T) in various fluoride phosphors is likely a pitfall caused by a diminishment in the optical path lengths of the spectrofluorometer stemming from lattice thermal expansion. We show that such anomalous enhancement of I PL is due to the increased phonon number that makes it possible to gain the parity and spin-forbidden 2 E g → 4 A 2g transitions rather than an extrinsic effect of lattice thermal expansion. The temperature dependence of the zero-phonon line emission intensity I ZPL may be a good indicator for deciding whether an observed anomaly of I PL is due to an intrinsic or an extrinsic effect because its intensity should in principle not be dependent on T. The experimental data on the Rb2GeF6:Mn4+ fluoride and Cs2WO2F4:Mn4+ oxyfluoride phosphors are presented as a direct verification of this. A discussion is also given on the 2 E g → 4 A 2g transition properties in connection with the inelastic light scattering spectroscopy.

Structural and optical characteristics of novel rare‐earth‐free red-emitting BaSn(PO4)2:Mn4+ phosphor

Red phosphor is an indispensable component in the development of warm white light-emitting diodes (w-LEDs). However, most of the current red phosphors suffer from shortages of high cost, complex synthesis process and harsh preparation conditions. In this paper, a phosphate-based red emitting phosphor without rare earth doping has been investigated. A series of xMn4+ ions (x = 0.00, 0.02, 0.04, 0.06, 0.08, 0.10 mmol) doping BaSn(PO4)2 phosphors were prepared by solid-state reaction. According to the X-ray diffraction (XRD) data, the phosphor belongs to monoclinic structure (C12/m1). The XRD refinement results show that with the increase of Mn4+ ions doping concentration, the β angle in the cell parameters of BaSn(PO4)2:xMn4+ phosphor gradually decreases, which indicates that the crystal cell is distorted. The morphology, elemental composition and molecular structure of the phosphor were studied by SEM, XPS and FT-IR. The band gap of the BaSn(PO4)2 host obtained by diffuse reflectance spectroscopy is about 3.59 eV, and the band gap decreases gradually with the Mn4+ ions doping content. From the room temperature fluorescence spectra, it is found that the phosphor emits red light when the excitation wavelength is 468 nm, and concentration quenching occurs at the doping concentration of x = 0.06. When the temperature rises to 423 K, the emission intensity of the phosphor remains at 76.7% of the original intensity at room temperature, and the activation energy Ea is calculated to be 0.1261 eV, indicating that the phosphor has excellent thermal stability. These results indicate that BaSn(PO4)2:xMn4+ is an excellent red phosphor.

Three-dimensional (3D) hierarchical Mn2O3 catalysts with the highly efficient purification of benzene combustion

A series of Mn2O3 catalysts were prepared by different hydrothermal temperatures and employed to the catalytic oxidation of benzene due to their high activity. The Mn-120 sample with three-dimensional (3D) hierarchical cube-like morphology mainly exposed (211) crystal plane exhibited the best catalytic activity for the oxidation of benzene and achieved the benzene conversion of 90% at 248 °C. Meanwhile, the best catalytic performance of the Mn-120 sample was attributed to the most amounts of the Mn3+ species and surface-adsorbed oxygen. With the increase of Mn3+ species, the oxygen binding capacity of Mn-120 was reduced, which could increase its oxygen mobility. The abundant adsorbed oxygen species of Mn-120 could improve the replenishment capacity of lattice oxygen species, and the reaction pathway of catalytic oxidation of benzene over MnO2 obeyed the Mars-Van-Krevelen (MVK) mechanism.

Magnetic Properties of Tetragonal Cobalt Manganese Ferrite Particles Prepared Using the Molten Salt Method

Both magnetization and magnetic anisotropy of CoMn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2-x</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> particles composed of the Jahn-Teller (JT) Mn <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> and Co <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> ions with an expected large magnetoelastic effect were investigated. CoMn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2-x</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> particles were prepared by using a molten salt method with KBr as a fluxing agent. A tetragonally distorted spinel structure was confirmed for x = 1.3 or higher. This suggests that an increase in Mn <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> ions causes JT distortion of c/a > 1. However, Mn <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> doping causes spin canting and decreased magnetization. A large saturation magnetization of M <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</sub> = 44 emu/g and high coercivity of H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</sub> = 4300 Oe were observed for the sample with x = 1.4 at 10 K. In addition, the magnetic anisotropy field, H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">A</sub> , and H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> increased with the increasing x from x = 1.3, where JT distortion was first observed.

Tuning the luminescence properties of Mn4+‐activated CaYAlO4 phosphor by co‐doping cations for indoor plant cultivation

AbstractTo fulfil the demands of high‐power plant growth lamps, cation co‐doping is an effective way to tune the photoluminescence properties of manganese (Ⅳ)‐activated aluminate phosphors. Therefore, we managed to synthesize a series of cations co‐doped CaYAlO4:xMn4+, mSr2+, M+ (M+ = Li+, Na+, and K+) (CYAO:Mn, Sr, M) far‐red‐emitting phosphors. The excitation spectrum of these phosphors contained two excitation bands, and the opposite effects of these two bands on the luminescence intensity have been observed with the increase of Mn4+ concentration. By adding 0.1 mol Sr2+ ions to replace Ca2+ site, the emission intensity and thermal stability of CYAO:Mn phosphors can be enhanced. Furthermore, the luminescence properties of CSYAO:Mn can be further improved by co‐doping monovalent alkali metal ions to serve as charge compensators, the increased number of Mn4+ luminescence centers. Moreover, 0.6 mol% Na+ can increase the initial emission intensity of the phosphors by 117% as the best ratio. The characteristic emission spectrum of the phosphors CYAO:Mn,Sr,M correspond to the phytochrome PFR of plants. These experiments and characterization results have certified that these phosphors have a potential application in indoor plants cultivation.

Dependence on sintering temperature of structure, optical and magnetic properties of La0.625Ca0.315Sr0.06MnO3 perovskite nanoparticles

Abstract In this study, La0.625Ca0.315Sr0.06MnO3 (LCSMO) nanoparticles were prepared by facile sol-gel method at low crystallization temperatures. Various test methods were used to characterize structure, optical and magnetic properties of LCSMO nanoparticles. X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) suggested complete crystallization of LCSMO nanoparticles sintered at 700 °C. In addition, unit cell volume and grain size increased with sintering temperature. Besides, X-ray photoemission spectroscopy (XPS) fitting results of Mn2p core level peaks confirmed the increase in Mn3+ ion concentration with sintering temperature, mainly attributed to formation of more oxygen vacancies. Raman microscopy and Fourier transform infrared spectrometry (FTIR) jointly depicted the existence of Mn–O bond, indicating that sintering temperature definitely impacted vibration mode of Mn–O and affected both crystal structure and performance. UV–vis optical band gap width of LCSMO nanoparticles sintered at 700 °C, 1000 °C, and 1500 °C decreased from 1.2 to 0.75 eV as sintering temperature increased, suggesting the semiconducting properties of nanoscale LCSMO particles. Magnetization dependent temperature (M-T) and magnetic field (M-H) measurements revealed degradation in magnetic properties of the specimens with temperature. Overall, LCSMO nanoparticles sintered at different sintering temperatures provided novel insights into properties of rare earth doped perovskite manganites.

Thickness dependence of structural, morphological and optical properties of Mn[sbnd]Co[sbnd]Ni[sbnd]O thin films grown by chemical solution deposition on SiO2/Si(1 0 0) substrate

Mn1.56Co0.96Ni0.48O4 (MCNO) thin films with different thicknesses ranging from 180 nm to 600 nm were deposited onto a SiO2/Si(1 0 0) substrate at 600 °C by using the chemical solution deposition method. The thickness dependent structural and optical properties of the MCNO films were investigated in this study. As identified by the SEM pictures and X-ray diffraction (XRD) spectra, all samples showed polycrystalline cubic spinel structure, and the stoichiometric status is improved with growing thickness according to XRD results. Spectroscopic ellipsometry spectra were measured in this study to investigate the thickness dependent optical properties of MCNO film in the range of 300–1000 nm. The samples showed three absorption structures locating at 1.6–1.9 eV, 2.6 eV, and above 3.5 eV, corresponding to the charge transfer transition involving 2p orbitals of O2− and 3d orbitals of Mn and Co ions, respectively. The absorption structure at above 3.5 eV decreases gradually as the thickness grows, while the peak around 1.6–1.9 eV weakens slightly before it enhances again with film thickness above 430 nm, which can be explained by a combined effect of crystallinity improvement and increase in Mn4+/Mn3+ ratio.