Dual substitution of host lattice ions to enhance the luminescence properties of Zn2TiO4:Cr3+ phosphor.

Near-infrared light sources have potential applications in many fields. Cr3+ is a good luminescence centre to prepare near-infrared phosphors. Improving the performance of existing near-infrared luminescent materials has indeed attracted great interest from researchers. The luminescence properties of Zn2TiO4:Cr3+ were improved by crystal field engineering strategies. Zn2+-Ti4+ was partially replaced using a Li+-Nb5+ ion pair based on the Zn2TiO4:Cr3+ phosphors. Luminescence Cr3+-activated luminescent materials are sensitive to changes in the local crystal structure and crystal field environment. Doping of Li+-Nb5+ increased the luminescence intensity up to 2.7 times that of the undoped sample. Also, the thermal stability of the phosphor was greatly increased by the replacement of Li+-Nb5+.

A novel Mn4+ -activated far-red Sr2 MgWO6 phosphor: synthesis, luminescence enhancement, and application prospect.

A novel far-red emitting phosphor Sr2 MgWO6 : Mn4+ was fabricated using high-temperature solid-state reaction. X-ray diffraction patterns, scanning electron microscopy images, and photoluminescence excitation and photoluminescence spectra for this phosphor were analyzed in detail. The analysis revealed that its emission ranged from 600 to 800 nm and peaked at 699 nm, which was attributed to the 2 Eg →4 A2g transition of Mn4+ under 314 nm excitation. Moreover, we introduced rare-earth Yb3+ ions into the Sr2 MgWO6 :Mn4+ to improve its far-red emitting intensity. The photoluminescence (PL) intensity of the Yb3+ co-doped phosphor was three times higher than that of the single-doped phosphor. Therefore charge compensation is an efficient approach to improving PL intensity. The phosphor emitted a far-red light that resembled the pigments essential for plant growth in terms of the absorption spectrum. Therefore, the obtained phosphor, Sr2 MgWO6 :0.006Mn4+ ,0.2Yb3+ , had the potential to be a new type of far-red luminescent powder for indoor plant growth LEDs.

Phosphors Ba2 LaTaO6 :Mn4+ and its alkali metal charge compensation for plant growth illumination.

A series of Mn4+ -doped and Mn4+ ,K+ -co-doped Ba2 LaTaO6 (BLT) double-perovskite phosphors was synthesized using a high-temperature solid-state reaction. The phase purity and luminescence properties were also studied. The optimum doping concentration of Mn4+ and K+ was obtained by investigating the photoluminescence excitation spectra and photoluminescence emission spectra. The comparison of BLT:Mn4+ phosphors with and without K+ ions shows that the photoluminescence intensity of K+ -doped phosphors was greatly enhanced. This is because there was a charge difference when Mn4+ ions were doped with Ta5+ ions in BLT. Mn4+ -K+ ion pairs were formed after doping K+ ions, which hinders the nonradiative energy transfer between Mn4+ ions. Therefore, the luminescence intensity, quantum yield, and thermal stability of phosphors were enhanced. The electroluminescence spectra of BLT:Mn4+ and BLT:Mn4+ ,K+ were measured. The spectra showed that the light emitted from the phosphors corresponded well with chlorophyll a and phytochrome PR . The results show that the BLT:Mn4+ ,K+ phosphors had good luminescence properties and application prospects and are ideal materials for plant-illuminated red phosphors.

A novel red phosphor Ca2 YNbO6 :Eu3+ for WLEDs.

Due to the advantages of good physicochemical properties, thermal stability, and optical properties, double perovskite compounds have received extensive attention. On this basis, a new type of red phosphor, Ca2 YNbO6 :xEu3+ , was synthesized using a high-temperature solid-phase method. Its phase purity, morphology, elemental composition, absorption spectrum, photoluminescence, thermal stability, and Commission Internationale de l'éclairage (CIE) chromaticity coordinates were thoroughly investigated. The results display that there is no impurity phase in the samples and the convergence factor Rwp = 14.2%; the microscopic particles are uniform and full, and the distribution of each element is uniform. The energy band gap ΔE is between 3.71 eV and 3.65 eV. The luminescence intensity is the best when the doped Eu3+ concentration x reaches 0.4, and emits 612 nm red light (5 D0 →7 F2 ) under 465 nm excitation, and the concentration quenching is attributed to a d-d interaction. The luminescence intensity at 425 K was still 75% of the room temperature luminescence intensity, which indicates that the thermal stability is extremely superior. The CIE chromaticity coordinates (0.6534, 0.3455) of the Ca2YNbO6:0.4Eu3+ phosphors are very close to National Television Standards Committee (0.670, 0.330), and the samples have low correlated colour temperature (2656 K) and high colour purity (99.90%). All findings suggest that Ca2 YNbO6 :Eu3+ can serve as a substitute for red phosphor in WLEDs.

Synthesis and photoluminescence properties of a novel green-emitting LiYGeO4 :Tb3+ long afterglow phosphor.

A new green luminescent phosphor, Li(Y1-x Tbx )GeO4 , was prepared using a high-temperature solid-phase method. The X-ray diffraction (XRD) measured spectrum agreed well with the standard card JCPDS No. 02-3479, indicating that it is a quaternary compound belonging to the space group of Pnma(62) with an orthogonal crystalline phase; the excitation and emission spectra measured using the phosphor spectrometer showed that it can be effectively excited by near-ultraviolet light at 378 nm and blue light at 482 nm, and produced excellent strong emission of green light at 550 nm. The afterglow test results show that the sample had a good long afterglow effect at lower doping concentrations; the thermal stability test results showed that its thermal burst activation energy ΔE ≈ 0.37 eV had its excellent thermal stability. The rare earth Tb3+ -doped green phosphor, LiYGeO4 :Tb3+ , has potential applications in household lighting, medical therapy, and optical storage.

Targeting CAIX with [64Cu]XYIMSR-06 Small Molecular Radiotracer Enables Noninvasive PET Imaging of Malignant Glioma in U87 MG Tumor Cell Xenograft Mice.

Carbonic anhydrase IX (CAIX) plays an important role in glioma cell proliferation, invasion, metastasis, and resistance to radiotherapy and chemotherapy. An effective and noninvasive PET molecular imaging agent targeting CAIX would help its diagnosis and treatment but is not currently available. Recently, a low-molecular-weight (LMW) CAIX targeting agent, [64Cu]XYIMSR-06, was reported to have significantly improved properties for targeting clear cell renal cell carcinoma (ccRCC). We are encouraged to investigate the feasibility of adapting this agent for the diagnosis and treatment of CAIX-overexpressing malignant glioma. In vitro cell uptake and binding affinity assays were used to verify the binding capacity of [64Cu]XYIMSR-06 to U87 MG tumor cells in which CAIX overexpression was confirmed. The U87 MG tumor-bearing mouse (in situ and subcutaneous) model was built, and mice were injected with the radiotracer and/or coinjected with acetazolamide (0.2 g/kg) as a blocking agent for noninvasive micro-PET imaging. Micro-PET imaging was performed at 2, 4, and 8 h postinjection. ROI (region of interest)-based semiquantification was performed in an orthotopic glioma tumor model. Biodistribution throughout each organ was performed at 2, 4, 4 h block, 8, and 24 h postinjection. Hematoxylin and eosin (HE) staining and immunofluorescence or immunohistochemistry (IF/IHC) staining were implemented postimaging to assess the expression of CAIX in tumor organs. In vitro, [64Cu]XYIMSR-06 exhibits greater uptake in glioma cells (high CAIX expression) than in HCT116 cells (low CAIX expression). The binding affinity of [64Cu]XYIMSR-06 to U87 MG cell lines reaches up to 4.22 nM. Both orthotopic and subcutaneous tumors were clearly visualized at 2-8 h postinjection. Biodistribution studies demonstrated a maximum tumor uptake of 3.13% ID/g at 4 h postinjection, and the tumor to brain ratio (T/brain) was 6.51 at 8 h postinjection. The ROI-based T/brain values were 7.03 and 5.46 at 2 and 8 h postinjection, respectively. Histopathological analysis confirmed the overexpression of CAIX in gliomas, and the area of CAIX-positive IF staining is extremely consistent with the morphology on micro-PET imaging. In this study, [64Cu]XYIMSR-06 demonstrated specific accumulation in CAIX-expressing U87 MG glioma tumors, indicating that the radiotracer has the potential for noninvasively monitoring and guiding personalized treatment of malignant glioma and other tumors overexpressing CAIX.

Thermally stable Cr3+-activated silicate phosphors for plant-growth LEDs and three-mode optical thermometry.

The structural, optical and temperature-dependent luminescence properties of Y2Mg2Al2Si2O12:Cr3+ phosphors were investigated for their multifunctional applications. The as-prepared phosphors exhibited an intense far-red emission band around 600-850 nm with a peak at 687 nm, which matches well with the absorption band of plant phytochromes. Importantly, the optimized sample showed excellent thermal stability and its emission intensity at 423 K maintained about 77% of that at 298 K. The potential application of the phosphors in plant-growth LED devices was also demonstrated. Furthermore, owing to the unique thermal quenching behavior of Cr3+, a three-mode luminescent thermometry system was designed based on fluorescent intensity (FL), fluorescent intensity ratio (FIR), and full width at half maximum (FWHM). The maximum temperature relative sensitivity (Sr) of each mode could reach 2.74% K-1, 1.09% K-1, and 1.47% K-1, respectively. These results indicate that the Y2Mg2Al2Si2O12:Cr3+ phosphors have potential applications for plant growth and optical thermometry.

Crystal structure and luminescence properties of a novel near-infrared phosphor LiAlO2:Fe3.

Cr3+-free near-infrared (NIR) phosphors are currently gaining significant attention in various application fields. A novel Fe3+-activated LiAlO2 NIR phosphor was successfully synthesized by high-temperature solid-state method. Under excitation of 391 nm and 467 nm, the phosphor emits near-infrared light with wavelengths ranging from 600 to 850 nm. The emission bands with peaks at 725 nm correspond to the transition from 4T1(4G) to the ground state energy level 6A1(6S). The optical band gap of LiAlO2 was calculated using Density Function Theory (DFT) and diffuse reflectance spectrum, respectively. The thermal stability of the sample was measured under 391 nm and 467 nm excitation, showing that the emission intensity at 413 K is 55.3 % and 52.4 % of the emission intensity at room temperature.

Dynamic Reconfiguration and Local Polarization of NiFe-Layered Double Hydroxide-Bi2MoO6- x Heterojunction for Enhancing Piezo-Photocatalytic Nitrogen Oxidation to Nitric Acid.

Constructing heterojunctions with vacancies has garnered substantial attention in the field of piezo-photocatalysis. However, the presence of interfacial vacancies can serve as charge-trapping sites, leading to the localization of electrons and hindering interfacial charge transfer. Herein, dual oxygen vacancies in the NiFe-layered double hydroxide and Bi2MoO6- x induced interfacial bonds have been designed for the piezo-photocatalytic N2 oxidation to NO3 -. Fortunately, it achieves sensational nitric acid production rates (7.23 mg g-1 h-1) in the absence of cocatalysts and sacrificial agents, which is 6.03 times of pure Bi2MoO6 that under ultrasound and light illumination. Theoretical and experimental results indicate that interfacial bonds act as "charge bridge" and "strain center" to break the carrier local effect and negative effects with piezocatalysis and photocatalysis for promoting exciton dissociation and charge transfer. Moreover, the strong electronic interaction of the interfacial bond induces internal reconstruction under ultrasound for promoting the local polarization and adsorption of N2, which accelerates the fracture of the N≡N bonds and reduces the activation energy of the reaction. The research not only establishes a novel approach for optimizing the combined effects of piezo-catalysis and photocatalysis, but also achieves equilibrium between the synergistic impacts of vacancies and heterojunctions.

Achieving Solar-Thermal-Electro Integration Evaporator Nine-Grid Array with Asymmetric Strategy for Simultaneous Harvesting Clean Water and Electricity.

Water evaporation is a ubiquitous and spontaneous phase transition process. The utilization of solar-driven interface water evaporation that simultaneously obtains clean water and power generation can effectively alleviate people's concerns about fresh water and energy shortages. However, it remains a great challenge to efficiently integrate the required functions into the same device to reduce the complexity of the system and alleviate its dependence on solar energy to achieve full-time operation. In this work, a multifunctional device based on reduced graphene oxide (RGO)/Mn3 O4 /Al2 O3 composite nanomaterials is realized by an asymmetric strategy for effective solar-thermal-electro integration that can induce power generation by water evaporation in the presence/absence of light. Under one sun irradiation, the solar-driven evaporation rate and output voltage are 1.74 kg m-2  h-1 and 0.778 V, respectively. More strikingly, the nine-grid evaporation/power generation array integrated with multiple devices in series has the advantages of small volume, large evaporation area, and high power generation, and can light up light-emitting diodes (LEDs), providing the possibility for large-scale production and application. Based on the high photothermal conversion efficiency and power production capacity of the RGO/Mn3 O4 /Al2 O3 composite evaporation/generator, it will be a promising energy conversion device for future sustainable energy development and applications.

Bulk Photovoltaic Current Mechanisms in All-Inorganic Perovskite Multiferroic Materials.

After the discovery of bulk photovoltaic effect more than half a century ago, ferro-electrical and magneto-optical experiments have provided insights into various related topics, revealing above bandgap open voltages and non-central symmetrical current mechanisms. However, the nature of the photon-generated carriers responses and their microscopic mechanisms remain unclear. Here, all-inorganic perovskite Bi0.85Gd0.15Fe1-xMnxO3 thin films were prepared by a sol-gel process and the effects of Gd and Mn co-doped bismuth ferrites on their microtopography, grain boundries, multiferroic, and optical properties were studied. We discovered a simple "proof of principle" type new method that by one-step measuring the leakage current, one can demonstrate the value of photo generated current being the sum of ballistic current and shift current, which are combined to form the so-called bulk photovoltaic current, and can be related to the prototype intrinsic properties such as magneto-optical coupling and ferroelectric polarization. This result has significant potential influence on design principles for engineering multiferroic optoelectronic devices and future photovoltaic industry development.

Electrodissolution-Coupled Hafnium Alkoxide Synthesis with High Environmental and Economic Benefits.

The conventional thermal method of preparing hafnium alkoxides [Hf(OR)4 , R=alkyl] - excellent precursors for gate-dielectric HfO2 on semiconductors - is severely hindered by its unsatisfactory environmental and economic burdens. Herein, we propose a promising electrodissolution-coupled Hf(OR)4 synthesis (EHS) system for green and efficient electrosynthesis of Hf(OR)4 . The operational principle of the electrically driven system consists of two simultaneous heterogeneous reactions of Hf dissolution and alcohol dehydrogenation, plus a spontaneous solution-based combination reaction. In applying ethanol as solvent and Hf metal as electrodissolution medium, we achieved waste-free production of high-purity hafnium ethoxide [Hf(OEt)4 ] with an equivalent "a concomitant" reduction in CO2 emission of 187.33 g CO2 per kg Hf(OEt)4 and a high net profit of 30 477 USD per kg Hf(OEt)4 . This system is very competitive with the thermal process, which unavoidably releases substantial waste and CO2 for a net profit of 27 700 USD per kg Hf(OEt)4 . We anticipate that the environmental and economic benefits of the EHS process could pave the way for its practical application.

Morphology optimization strategy of flower-like CoNi2S4/Co9S8@MoS2 core@shell nanocomposites to achieve extraordinary microwave absorption performances.

Morphology optimization is an effective strategy to take full advantage of interface polarization for the improvement of electromagnetic wave attenuation capability. Herein, a general route was proposed to produce the flower-like core@shell structured MoS2-based nanocomposites through a simple hydrothermal process. Through the in-situ hydrothermal reaction between the Mo and S sources on the surface of CoNi nanoparticles, flower-like core@shell structured CoNi2S4/Co9S8@MoS2 nanocomposites could be successfully synthesized. By regulating the hydrothermal temperature, the flower-like geometrical morphology of samples could be effectively optimized, and the as-prepared sample (S2) synthesized at 200 °C displayed very excellent flower-like morphology compared to the samples (S1 and S3) obtained at 180 and 220 °C. Owing to the excellent interface polarization effect, the as-prepared S2 presented the evidently superior comprehensive microwave absorption properties in terms of strong aborption capability, wide absorption bandwidth and thin matching thicknesses compared to those of S1 and S3. The as-prepared core@shell structured CoNi2S4/Co9S8@MoS2 sample with very excellent flower-like morphology simultaneously displayed the minimal reflection loss of -50.61 dB with the matching thickness of 2.98 mm, and the effective absorption bandwidth of 8.40 GHz with the matching thickness of 2.36 mm. Therefore, we provided a general route for the production of flower-like core@shell structured MoS2-based nanocomposites, which could make the best of interface polarization to develop high-efficiency microwave absorbers.

A generalizable strategy for constructing ultralight three-dimensional hierarchical network heterostructure as high-efficient microwave absorber.

Using previous models and theories to construct and develop high-efficient microwave absorbers (MAs) should be a strategic and effective ways to optimize the electromagnetic wave attenuation. Herein, the ultralow density and flexible graphene oxide foam (GOF) and reduced graphene oxide foam (RGOF)/MoS2 nanosheets were designed and fabricated by the method of chemical vapor deposition and hydrothermal reaction. The obtained GOF and RGOF/MoS2 samples exhibited very excellent microwave absorption properties while their densities were merely 0.0082 and 0.0084 g•cm-3, respectively. More importantly, benefiting from the excellent synergistic effect between RGOF and MoS2, the designed RGOF/MoS2 well inherited the combined advantages of GOF and MoS2 in terms of strong absorption abilities, broad absorption bandwidth and thin matching thicknesses. The values of minimum reflection loss and effective frequency bandwidth for RGOF/MoS2 sample could reach up to -62.92 dB with the matching thickness of 2.27 mm and 4.48 GHz with the matching thickness of 2.12 mm, which were very desirable for high-performance MAs. Moreover, the obtained results indicated that the microwave absorption properties of RGOF/MoS2 sample could be further optimized by regulating the MoS2 content. Therefore, a new and effective strategy was proposed to develop high efficiency MAs with ultra-lightweight, wide-band, thin thickness and strong absorption capabilities.

Regulation of Photovoltaic Response in ZSO-Based Multiferroic BFCO/BFCNT Heterojunction Photoelectrodes via Magnetization and Polarization.

Multiferroic devices have attracted renewed attention in applications of photovoltaic devices for their efficient carrier separation driven by internal polarization, magnetization, and above-bandgap generated photovoltages. In this work, Zn2SnO4-based multiferroic Bi6Fe1.6Co0.2Ni0.2Ti3O18/Bi2FeCrO6 (BFCNT/BFCO) heterojunction photoelectrodes were fabricated. Structural and optical analyses showed that the bandgap of the spinel Zn2SnO4 is ∼3.1 eV while those of Aurivillius-type BFCNT and double-perovskite BFCO are 1.62 and 1.74 eV, respectively. Under the simulated AM 1.5G illumination, the as-prepared photoelectrodes delivered a photoconversion efficiency (η) of 3.40% with a short-circuit current density (Jsc), open-circuit voltage (Voc), and fill factor (FF) of 10.3 mA·cm-2, 0.66 V, and 50.4%, respectively. Analyses of adjustment of an applied electric and magnetic field on photovoltaic properties indicated that both magnetization and polarization of multiferroics can effectively tune the built-in electric field and the transport of charge carriers, providing a new idea for the design of future high-performance multiferroic oxide photovoltaic devices.

Multiferroic oxide BFCNT/BFCO heterojunction black silicon photovoltaic devices.

Multiferroics are being studied increasingly in applications of photovoltaic devices for the carrier separation driven by polarization and magnetization. In this work, textured black silicon photovoltaic devices are fabricated with Bi6Fe1.6Co0.2Ni0.2Ti3O18/Bi2FeCrO6 (BFCNT/BFCO) multiferroic heterojunction as an absorber and graphene as an anode. The structural and optical analyses showed that the bandgap of Aurivillius-typed BFCNT and double perovskite BFCO are 1.62 ± 0.04 eV and 1.74 ± 0.04 eV respectively, meeting the requirements for the active layer in solar cells. Under the simulated AM 1.5 G illumination, the black silicon photovoltaic devices delivered a photoconversion efficiency (η) of 3.9% with open-circuit voltage (Voc), short-circuit current density (Jsc), and fill factor (FF) of 0.75 V, 10.8 mA cm-2, and 48.3%, respectively. Analyses of modulation of an applied electric and magnetic field on the photovoltaic properties revealed that both polarization and magnetization of multiferroics play an important role in tuning the built-in electric field and the transport mechanisms of charge carriers, thus providing a new idea for the design of future high-performance multiferroic oxide photovoltaic devices.

Direct Anterior Approach Versus Posterolateral Approach in Total Hip Arthroplasty: A Systematic Review and Meta-analysis of Randomized Controlled Studies.

OBJECTIVE: To compare the early rehabilitation effects of total hip arthroplasty (THA) with the direct anterior approach (DAA) versus the posterior approach (PA). METHODS: We searched PubMed, Embase, Web of Science, the Cochrane Library, and Google databases from inception to June 2019 to select studies that compared the DAA and PA for THA. Only randomized controlled trials (RCT) were included. Two researchers independently screened studies for inclusion, extracted data, and assessed the methodological quality. A meta-analysis was conducted using RevMan 5.3 software provided by Cochrane Assisted Network. RESULTS: A total of 932 patients underwent THA. There were 467 cases in group DAA and 465 cases in group PA. There was a significant difference in the incidence of lateral femoral cutaneous nerve injury between DAA and PA groups (RR = 38.97, 95% CI: 7.89-192.57, P < 0.05). DAA was associated with less pain compared with PA [WMD = -0.65, 95% CI (-0.91-0.38), P < 0.05]. There was no significant difference in operation time, hospitalization stay, and intraoperative bleeding volume. Moreover, in supplementary data, the number of acetabular prostheses in Lewinnek's safety zones in DAA was more than that in the PA group (RR = 1.20, 95% CI [1.04-1.39], P < 0.05), and the time of discontinuation of walking aids in the DAA group was earlier than that in the PA group (WMD = -11.05, 95% CI [-17.79-4.31], P < 0.05). CONCLUSION: The DAA total hip arthroplasty has comparable results with PA, with earlier postoperative functional recovery, less postoperative pain scores, and higher incidence of lateral femoral cutaneous nerve injury. The results need to be validated by large-sample, high-quality RCT studies, and long-term follow-up of complications.

Outstanding comprehensive performance versus facile synthesis: Constructing core and shell-interchangeable nanocomposites as microwave absorber.

It is still a great challenge to develop high-performance microwave absorption materials (MAMs). Herein, we first proved the excellent synergistic effect of Fe3O4/MoS2 heterostructure based on the theoretical calculations. To effectively utilize the synergistic effect and morphology, core and shell-interchangeable Fe3O4@MoS2 and MoS2@Fe3O4 nanocomposites (NCs) were elaborately constructed. By controlling the hydrothermal temperature, different MoS2 morphologies and contents of Fe3O4@MoS2 NCs were produced, which simultaneously displayed the optimal reflection loss (RL) values (~-50 dB), broad absorption bandwidth (⩾5.0GHz) and high chemical stabilities. With the synthesis temperature increasing from 170 °C to 200 °C, their outstanding microwave absorption (MA) capabilities moved towards the high frequency region and thin matching thickness. Impressively, the Fe3O4@MoS2 obtained at 200 °C presented a minimum RL value of -50.75 dB with the thickness of 2.90 mm and an absorption bandwidth of 5.0 GHz with the thickness of 1.71 mm, and the excellent MA capabilities (RL values <-30 dB) with the low matching thicknesses (<2 mm) could be observed in the frequency range of X and Ku bands. Moreover, compared to the reverse structure MoS2@Fe3O4, the core@shell structure Fe3O4@MoS2 exhibited evidently superior MA comprehensive properties in terms of low optimal RL value, broad absorption bandwidth and high chemical stability, which could be ascribed to the improved impedance matching and microwave attenuation characteristics. Generally, the proposed flower-like core@shell structure Fe3O4@MoS2 NCs presented very extraordinary MA comprehensive properties, which were very attractive candidates for high-performance MAMs.

Improved ferroelectric properties and band-gap tuning in BiFeO3 films via substitution of Mn.

Multiferroic BiFe1-x Mn x O3 (x = 0, 0.04, 0.08, 0.12) films have been prepared on Pt/Ti/SiO2/Si and ITO/glass substrates via the solution-gelation technique. The impacts of Mn doping of BFO thin films on the structure, morphology, leakage current, ferroelectric properties and optical band gap have been systematic investigated. From the XRD patterns, all samples match well with the perovskite structure without an impurity phase and the thin films exhibit dense and smooth microstructure. A leakage current density of 1.10 × 10-6 A cm-2 which is about four orders of magnitude lower than that of pure BiFeO3 was observed for the 8% Mn doped BFO thin film at an external electric field <150 kV cm-1. An increase in the remnant polarization with Mn substitution was observed, with a maximum value of ∼19 µC cm-2 for the 8% Mn-substituted film. Moreover, optical absorption spectra indicate that the doping of Mn has an effect on the energy band structure. Compared with pure BiFeO3, Mn doped thin films present an intense red shift as shown in the UV-visible diffuse absorption together with the decreased direct and indirect optical band gaps. In addition, this work gives insight into the relationship between ferroelectric remnant polarization and band-gap and finds that the optical band gap decreases with the increase of residual polarization.

Ferroelectric, Dielectric, Ferromagnetic, and Magnetoelectric Properties of BNF-NZF Bilayer Nanofilms Prepared via Sol-Gel Process.

Bilayer magnetoelectric (ME) nanofilms composed of Bi0.9Nd0.1FeO3 (BNF) and Ni0.55Zn0.45Fe2O4 (NZF) were fabricated on the Pt(111)/Ti/SiO2/Si(100) substrates via sol-gel and a subsequent rapid thermal process with different growth sequences of BNF and NZF forming the following layered structures: BNF/NZF and NZF/BNF. The phase composition, microstructure, and ferroelectric, dielectric, ferromagnetic, and ME coupling properties of the composites were investigated at room temperature. Structural characterization by X-ray diffraction and scanning electron microscopy showed that there are no other impurity phases but BNF and NZF, and the nucleation barrier caused that it is easier for NZF and BNF to grow on each other rather than on the surface of Pt/Ti/SiO2/Si. The tests of the physical properties indicated that such heterostructures present both good ferroelectric, ferromagnetic, and dielectric properties and the in-plane ME coupling coefficient α E at room temperature but some discrepancies also exist, which can be attributed to an interfacial effect, in other words, the deposition sequences of the constituent phases have a great influence on the properties of bilayer films.