Structure, Dielectric and Multiferroic Properties of Bi0.85Nd0.15Fe0.98Zr0.02O3 in Ba and Ti Co-Doping

Multiferroic (1- x)Bi0.85Nd0.15Fe0.98Zr0.02O3- xBaTiO3 (x = 0, 0.275, 0.3, 0.325, 0.35, 0.375, 0.4) ceramics were synthesized by the conventional solid state reaction method. X-ray diffraction studies confirm the phase transition from rhombohedral perovskite structure to pseudocubic structure with the introduction of BaTiO3. The results of the refinement indicate the BaTiO3 is successfully doped into the crystal lattice. The microstructure analysis shows that the average grain size increases with the introduction of BaTiO3. An increase in remanant polarization has been achieved at room temperature as the BaTiO3 concentration increasing. A greatly reduced leakage current density of about two orders of magnitude is observed in x = 0.375 (J = 2.4×10− 7 A/cm2) ceramic. The dielectric properties have been enhanced by the addition of BaTiO3, which is attributed to the reduction in Fe2+ ions and oxygen vacancies. Due to the grain effect and structure transition caused by the doping of BaTiO3, the magnetization reveals a slight decrease while the coercive field for x = 0.325 (Hc = 1785.8 Oe) increases to 6.4 times of the undoped ceramic.

Effect of Pr, Mn Doping on the Structure and Properties of BiFeO3

The powders of Bi1-xPrxFeO3 (x = 0, 0.05, 0.1) and Bi0.95Pr0.05Fe1-yMnyO3 (y = 0.05, 0.1) were prepared by hydrothermal method. The effects of Pr and Mn doping content on the structure, morphology, magnetic, and photocatalytic properties of BiFeO3 (BFO) have been studied. X-ray diffraction (XRD) demonstrated that the compounds are distorted rhombohedral perovskite structure without any other heterogeneity and structural transition. Field emission scanning electron microscope (FESEM) reflected that the surface of compounds is a dense, agglomerated sphere, and the morphology changes with the addition of Pr, Mn. Energy spectrum analysis (EDS) shows that the Bi0.95Pr0.05Fe0.95Mn0.05O3 sample is mainly composed of 5 elements (Bi, Fe, O, Pr, Mn), and the atomic ratio matches the formula well. Integrating the vibrating sample magnetometer (VSM) into the physical property measurement system (PPMS-9) shows that the introduction of Pr3+and Mn2+ ions can enhance the magnetic properties of BFO at room temperature. In addition, doping with Pr3+ and Mn2+ ions can improve the photocatalytic performance of BFO, and with the increase of Mn2+ concentration, the photocatalytic performance of BFO first rises and then decreases, and its catalytic performance is getting better and better.

Infrared Emissivity of La0.8Sr0.2MnO3 under 0.76-2.5 μm and 2.5-500 μm Radiation Fields

La0.8Sr0.2MnO3 was prepared to investigate the infrared emissivity of the sample under 0.76-2.5 μm and 2.5-500 μm infrared fields. The sample exhibited characteristic peaks of rhombohedral perovskite structure at 298-318 K, and split of the main peak weakened with increasing temperature. Intensity of the ferromagnetic resonance peak enhanced with increasing temperature, and the peak was shifted toward high magnetic field. A weak paramagnetic resonance peak appeared at 318 K, indicating that ferromagnetic-paramagnetic transition was occurring. The temperature of the sample under 2.5-500 μm field was higher than that under 0.76-2.5 μm. The emissivity of the sample increased with radiation time under 2.5-500 μm, but it had no obvious changes at about 0.665 under 0.76-2.5 μm. The emissivities at the same temperature fields were higher than those under 0.76-2.5 μm and 2.5-500 μm fields, respectively. It suggested that 0.76-2.5 μm and 2.5-500 μm radiations had inhibition effect on emissivity of La0.8Sr0.2MnO3.

BiFeO3 codoping with Ba, La and Ti: Magnetic and structural studies

Conventional solid state reaction method, from oxides and carbonates, was employed to prepare bismuth (Bi)-based multiferroic systems. The undoped BiFeO3 (BFO) and the codoped system with Ba, La and Ti (Bi[Formula: see text]BaxFe[Formula: see text]TiyO3, Bi[Formula: see text]BaxLazFe[Formula: see text]TiyO3) with x,y,[Formula: see text] were prepared stoichiometrically and sintered at two different temperatures. The structural and magnetic properties were investigated at room temperature. XRD measurements confirm the obtaining of the rhombohedral perovskite structure of the BFO family system. For the undoped system, some reflections of undesired phases are present for two different sintering temperatures, while for the doped system only one phase is present for both temperatures. The magnetic characterization at room temperature revealed remarkable differences between the ceramic samples. The results show that for undoped BFO system, spontaneous magnetization is not observed at room temperature. Nevertheless, in doped one, a well-defined ferromagnetic behavior is observed at room temperature, possible, due to the suppression of the spatially modulated spin structure of BFO promoted by the reduction of the rhombohedral distortion and the weakening of the Bi–O bonds. The XPS results confirm the presence of oxygen vacancies and the coexistence of Fe[Formula: see text] and Fe[Formula: see text] in all the studied samples. Calorimetric measurements reveal that the dopant incorporation has not a direct effect in Néel temperature but possibly yes in ferroelectric-paraelectric transition.

Effects of Sm and Mn Co-Doping on Structural and Optical Properties of BiFeO3 Thin Films Prepared by Sol-Gel Technique

(Bi1-xSmx)(Fe0.95Mn0.05)O3(x=0.00, 0.03 and 0.06) thin films were deposited on the quartz substrates by sol-gel technique. The results of X-ray diffraction patterns indicated all thin films had rhombohedral perovskite structure. Moreover, the Sm and Mn co-doping at A-and B-site of BiFeO3resulted in the structural distortion. Scanning electron microscope measurements exhibited that the uniform surface morphology could be obtained by co-doping and the average grain size of the films decreased with increasing Sm content. Furthermore, the fundamental absorption edges ofxBSFMO films showed a blue shift with the increase of Sm content which can be observed in transmittance spectra. The optical band gap of the thin films forx= 0.00, 0.03 and 0.06 can be expressed by (0.84x+2.62) eV, which is due to the Burstein-Moss effect.

Non-relaxor responses of highly ordered Pb(Sc1/2Nb1/2)O3 crystals

Pb(Sc1/2Nb1/2)O3 crystals have been grown by the top seeded solid solution technique and present a pure rhombohedral perovskite structure.