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A new relaxor ferroelectric ceramics, Sr 4 CaBiTi 3 Nb 7 O 30, were prepared. The microstructure, morphology, dielectric, and ferroelectric properties were studied. The ceramics were found that growing in some directions preferentially. Two dielectric relaxations were observed below the Burns temperature T B = 460 K and relaxation-I can be described by the VogelFulcher law. The Curie-Weiss constant (C) of 1.33 3 10 5 K confirms the displacive-type ferroelectric phase transition. The ceramics exhibit the first-order diffuse ferroelectric phase transition feature. The diffusion exponent varies from 1.99 to 1.92 with different applied frequencies. Room-temperature (RT) polarization was evaluated, and P r = 2.6 lC/cm 2, E c = 15.2 kV/cm values were obtained. The high breakdown voltage (≥80 kV/cm) and low leakage current confirmed the high quality of Sr 4 CaBiTi 3 Nb 7 O 30 ceramics. All of these features suggest that Sr 4 CaBiTi 3 Nb 7 O 30 may be used to substitute lead-based relaxor ferroelectric materials for environmental friendly. Raman spectra and polarization measured at different temperatures attribute the high-and low-temperature dielectric relaxation to flipping and breathing of polar nanoregions, respectively.

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Ba1-xLaxTi0.96Mn0.04O3 ceramics (x = 0, 3%, 7%) were prepared by a modified Pechini method and the structure, morphology, magnetic and electric properties have been investigated. X-ray diffraction analysis reveals La3+ ions could suppress the formation of hexagonal phase effectively. The cell parameter c decreases firstly and then increases with the increase of La content, which indicates that La ions have been incorporated into the lattice of BaTi0.96Mn0.04O3, and that Mn ions transform from high valence to low valence. The magnetization, polarization and leakage currents are also influenced by La doping greatly. Detailed analysis of magnetic variation with structural change attributes the room temperature ferromagnetism to double exchange interactions between Mn3+ and Mn4+ ions.

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Background: Coronavirus disease 2019 (COVID-19) patients suffer from anxiety, depression, and sleep disorder due to isolation treatment and other reasons. Whether life interventions can be an alternative therapy for COVID-19 patients, accompanied with anxiety, depression, and sleep disorder, is controversial. Therefore, we conducted a meta-analysis and systematic review to evaluate the effects of life interventions on anxiety, depression, and sleep disorder in COVID-19 patients to provide some guidance for clinical application. Methods: The randomized controlled trials related to the life intervention and COVID-19 from inception to February 2021 will be searched. The following databases are our focused areas: the Cochrane Central Register of Controlled Trials, PubMed, MEDLINE, EMBASE, Web of Science, China National Knowledge Infrastructure, Chinese Biomedical Literature Database, and Wan Fang Database. Two investigators would independently screen the literature according to the inclusion and exclusion criteria, extract data, and evaluate the risk of bias in the included studies. Meta-analysis was performed with RevMan 5.3 software. Results: The results will provide a high-quality synthesis of current evidence for researchers in this subject area. Conclusion: The conclusion of our study will provide evidence for the judgment of whether life intervention is an effective intervention on COVID-19 patients. PROSPERO registration number: CRD42020199802.

Sr4CaSmTi3Nb7O30 ceramics are synthesized and indexed as tetragonal tungsten bronze structure. The dielectric behavior and ferroelectric nature are investigated. Three dielectric anomalies are observed. The phase transition is a displacive phase transition with some diffusive characteristics, which indicates possible compositional variations within the materials on the microscopic scale. The weak distortion disappears in cooling process for differential scanning calorimetry measurement, and the large depression of Curie—Weiss temperature T0 indicates the difficulty in forming macroferroelectric domain. The ferroelectric nature in these filled tungsten bronze niobates originates from the off-center displacement of B-site cations, but they are primarily dominated by A-site cation occupation. Both the radius and the valence of A1-site cations play an important role on ferroelectric properties of the filled tungsten bronze compounds. Existence of spontaneous polarization with a remanent polarization of 0.16 μC/cm2 a coercive field of Ec = 11.74 kV/cm confirms the room-temperature ferroelectric nature of Sr4CaSmTi3Nb7O30 ceramics.

Sr4CaRTi3Nb7O30 (R = Ce, Eu) tungsten bronze ceramics are prepared by a standard solid state reaction method. The effects of A1 site occupation on the dielectric and ferroelectric properties of Sr4CaRTi3Nb7O30 (R = Ce, Eu) tetragonal tungsten bronzes are investigated. The Sr4CaCeTi3Nb7O30 shows a normal transition behavior due to the closer size ion occupation in A1 sites, which could suppress the distortion of B2 octahedra effectively. Sr4CaEuTi3Nb7O30 ceramic exhibits two dielectric anomalies, which might be related to the fact that the large radius difference between Ca2+ and Eu3+ could lead to the uneven distribution of Ca2+ and Eu3+ in A1 sites and form two slightly different kinds of compositions with different transition temperatures in the structure. Our results indicate that the ionic radius difference in A1 sites plays an important role in determining the dielectric and ferroelectric natures of the filled tungsten bronze ceramics. Polarization—electric field (P—E) curves are evaluated at room temperature and both of them show hysteresis loops. Sr4CaCeTi3Nb7O30 shows a fat hysteresis loop, indicating the long-range ferroelectric order in the ceramic. The current density—electric field (J—E) curves are measured at room temperature with a largest leakage current density of ∼ 10−6 A/cm2, indicating that their leakage currents are rather low.