Multiferroic ceramics of Bi5Fe1-xCo x Ti3O15(x=0.0—0.6) are synthesized by the conventional solid state reaction, and their microstructure,magnetic and ferroelectric properties are investigated. X-ray diffraction patterns show that a four-layer Aurivillius phase is formed in each sample with a suggested structural transformation at heavy doping of Co ions. The Raman results demonstrate that Co ions enter into the lattice,occupy the B-sites in the BFCT-x and have an effect on the order occupancy of cations at B sites. It is found that the Co ion modification induces remarkable ferromagnetism (FM) at room temperature with a greatest remanent magnetization (2M r) of 2.3 memu/g at x=0.5,which is three orders of magnitude larger than that of Bi5Ti3FeO15(BFTO). All samples with Co doping have ferroelectricity (EM). The remanent polarization (2P r) reaches a value of 11 μC/cm2 at x=0.1,which is about 38.2% higher than that of BFTO,and then decreases when 0.2≤x≤0.4 and increases again at x=0.5 and 0.6. Of all materials,the sample of x=0.5 is best in both good FE and FM.
From May to October 2004, the seasonal changes of K, Ca, and Mg contents and accumulation in Calamagrostis angustifolia, the dominant species in the typical meadow and marsh meadow communities of Sanjiang Plain, were studied. There was a greater difference in the seasonal changes of K, Ca, and Mg contents in different parts of typical meadow C. angustifolia (TMC) and marsh meadow C. angustifolia (MMC). The K content in aboveground parts of the two communities had an overall decreasing trend, according with linear model K = A + B(t), the Ca content had a smaller change in stem but an overall increasing trend in leaf and vagina, being accorded with parabola model Ca = A +B1t + B2t2 and exponential growth model Ca = Aexp(t/B1) + B2, respectively, while the Mg content had the greatest change in stem but changed relatively smoothly in leaf and vagina. The differences of K, Ca, and Mg contents in different parts of TMC and MMC were obvious. The K content in aboveground parts of TMC was generally higher than that of MMC, while the Ca and Mg contents in the root and vagina of MMC were higher than those of TMC. The K, Ca, and Mg storage and accumulation in different parts of TMC and MMC also differed. Root had the greatest K, Ca, and Mg storage, occupying 63.82 +/- 23.19%, 78.68 +/- 15.44%, and 76.48 +/- 19.06% of the total storage in TMC and 85.23 +/- 9.20%, 93.51 +/- 3.46%, and 92.39 +/- 3.22% in MMC, respectively. The aboveground parts of TMC had a higher storage of K, Ca and Mg than those of MMC, while the root was in adverse. Such a difference was mainly due to ecological characteristics of C. angustifolia and its habitat conditions.
Salt-affected soils is an important soil resource. Understanding fertilizer and salinity interaction are of great economic importance for improving crop yield and fertilizer use efficiency. A pot experiment was carried out to study the application of nitrogen (N) for ameliorating salt stress in wheat grown in the coastal saline soil of the Yellow River delta. Several controlling levels of salinity and nitrogen (0.7, 1.7, 2.7 g/kg, and 135, 270, and 405 kg/ha) were designed in a pot experiment in a stable water content state to investigate the N and salt interaction on soil properties and winter wheat growth characteristics. The results showed that the dry weight of winter wheat was promoted by salinity in the early growth stage (20 days), then it was gradually inhibited by nitrogen fertilizer. When winter wheat was grown by 54 days, the N and salinity had significant effects on the biomass of winter wheat. The nitrogen content of wheat shoot and root was mainly affected by N addition usage, and the largest value was obtained in 270 kg/ha N dosage treatments. The higher the salt content existed in the soil, the lower the growth rate shown in wheat cultivation. Under saline conditions, the N fertilizer application amount should be controlled to no more than 270 kg/ha, so that it could greatly promote wheat growth. Reasonable fertilizer usage could significantly contribute to crop yield and food quality of the saline agriculture in the Yellow River delta.
The dielectric and ferroelectric properties of Nd-doped Bi_4Ti_3O_(12)() ceramics are investigated.The dependences of 2P_r() and 2E_c() on the Nd content are observed.2P_r() increases with doping,and maximizes at the Nd content of 0.6,then decreases.2E_c() increases with Nd-doping gradually.The results show that the decrease of t_c() indicates the relief of lattice distortion.As the Nd content is higher than 0.6,t_c() decreases faster and BNdT-x(x0.6) exhibits typical relaxational characteristics.The dependence of dielectric loss on the Nd content indicates the oxygen vacancy concentration decreases and the mobility of domain wall increases with doping,which are responsible for the increase of 2P_r.
Asymmetric heterointerfaces that bridge two nonisostructural oxides provide valuable opportunities for novel emergent phenomena that may be unavailable for symmetric interfaces. Here we present a theoretical investigation on three different asymmetric interfaces consisting of the infinite-layer nickelate $\mathrm{LaNi}{\mathrm{O}}_{2}$ and the perovskite manganite $\mathrm{LaMn}{\mathrm{O}}_{3}$ (type A, B and C). An alternative crystal geometry, pyramid, is introduced when the planar-type $\mathrm{LaNi}{\mathrm{O}}_{2}$ and the $\mathrm{LaMn}{\mathrm{O}}_{3}$ are jointed at the interface, resulting in strong charge and orbital reconstruction. For type A interface, the magnetic moment per Mn ion has increased by 10% due to the replacement of $\mathrm{Mn}{\mathrm{O}}_{6}$ by $\mathrm{Mn}{\mathrm{O}}_{5}$. For type B interface, in contrast, the magnetic moment grew by 26% for the interfacial Ni ions due to the strong charge transfer between center nickel and apical oxygen. For type C interface, only slightly enhanced $\mathrm{Mn}{\mathrm{O}}_{6}$ distortions are observed and thus the change of charge and orbital occupancy are negligible. Our results demonstrated that an interface-selective orbital occupancy, where the Mn ${e}_{\mathrm{g}}$ orbital preferential occupation alternated from the out-of-plane ${\mathrm{d}}_{3{z}^{2}\ensuremath{-}{r}^{2}}$ state at type A interface to nearly degenerate at type C interface and then to in-plane ${\mathrm{d}}_{{x}^{2}\ensuremath{-}{y}^{2}}$ state at type B interface. The values of relative change of Mn ${e}_{\mathrm{g}}$ orbital occupancy are 15%, 2%, and \ensuremath{-}21%, respectively. The values of relative change at type A and B interface are larger than that achieved by strain $(\ensuremath{\sim}5%)$ or symmetric interface design (10%). Therefore, interface reconstructions lead to unusual electronic properties, opening space for the advancement of oxide electronics.
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