In the present work the influence of rare earth elements concentration (0-10at-%) on BiFeO
3
:RE (RE=Gd
3+
, Dy
3+
, Nd
3+
) ceramics were studied. All ceramic powders were synthesized by ...conventional ceramic method using high purity raw materials (>99,9%), and subsequently sintered by free sintering and cold pressing method. To analyze the powders and ceramics more the XRD, EDS, SEM, and DTA were performed.
The series of polycrystalline ceramic powders, Bi sub(1-x)Nd sub(x) FeO sub(3) (x = 0.1-1) was successfully synthesized by mixed oxide method followed by pressureless sintering. X-ray diffraction and ...Mossbauer spectroscopy were used as complementary methods to study structure and hyperfine interactions of the samples. It was found that with an increase of Nd content, within the range of x = 0.2-0.3 a structural phase transition from rhombohedral to orthorhombic system occurs. The lattice parameters and unit-cell volume decrease with an increase of Nd concentration. The Mossbauer spectra registered for Bi sub(1-x)Nd sub(x)FeO sub(3) are characterized by sextets with slightly broadened lines and reveal distributions of hyperfine magnetic fields. It was found that the value of the hyperfine magnetic field induction monotonically increases with Nd content. The mean values of isomer shift are typical for Fe super(3+) ions in a high spin state and slightly decrease from 0.40 mm s super(-1) for x = 0.3 to 0.37 mm s super(-1) for x = 0.9. The small value of quadrupole shift confirms octahedral coordination of the iron ions. The structural transition is accompanied by an increase of isomer shift and a change of sign of quadrupole shift.
The structure, hyperfine interactions and magnetic properties of the series of multiferroic Bi(m+1)Ti(3)Fe(m-3)O(3m+3) Aurivillius compounds with m=4-8 were studied using X-ray diffraction, (57)Fe ...Mossbauer spectroscopy and vibrating sample magnetometry. Samples were prepared by the conventional solid-state sintering method. Bulk magnetic measurements showed that for m=4 the compound is paramagnetic down to 2 K while in the compound with m = 5 the antiferromagnetic type transition was observed at 11 K. In the case of compounds with m = 6-8 much more complex magnetic behavior was found. For these compounds a gradual spin freezing and antiferromagnetic spin glass-like ordering were observed on decreasing temperature. The temperature of spin glass freezing was determined as 260, 280 and 350 K for m = 6, 7 and 8, respectively. Room-temperature Mossbauer spectra of all the compounds studied confirm their paramagnetic state. However, liquid nitrogen and liquid helium temperature measurements reveal magnetic ordering with a residual paramagnetic phase contribution for the compounds with m = 5-8.
The structure, hyperfine interactions and magnetic properties of the series of multiferroic Bim+1Ti3Fema3O3m+3 Aurivillius compounds with m=4a8 were studied using X-ray diffraction, 57Fe Mossbauer ...spectroscopy and vibrating sample magnetometry. Samples were prepared by the conventional solid-state sintering method. Bulk magnetic measurements showed that for m=4 the compound is paramagnetic down to 2 K while in the compound with m=5 the antiferromagnetic type transition was observed at 11 K. In the case of compounds with m=6a8 much more complex magnetic behavior was found. For these compounds a gradual spin freezing and antiferromagnetic spin glass-like ordering were observed on decreasing temperature. The temperature of spin glass freezing was determined as 260, 280 and 350 K for m=6, 7 and 8, respectively. Room-temperature Mossbauer spectra of all the compounds studied confirm their paramagnetic state. However, liquid nitrogen and liquid helium temperature measurements reveal magnetic ordering with a residual paramagnetic phase contribution for the compounds with m=5a8.
In this paper, the synthesis conditions for fabrication of Bi sub(1-x)Nd sub(x)FeO sub(3) (for x = 0.6-1) ceramics are reported. The mixed oxide method was employed for the ceramics' fabrication. Bi ...sub(1-x)Nd sub(x)FeO sub(3) ceramics were prepared from simple oxide powders Bi sub(2)O sub(3), Nd sub(2)O sub(3) and Fe sub(2)O sub(3). The goal of this study was to investigate the way the fabrication process influences prepared powders and samples of Bi sub(1-x)Nd sub(x)FeO sub(3) as microstructure and structure. For this reason, samples were characterized using various techniques. X-ray diffraction study was carried out for phase determination and lattice parameter calculations. Scanning electron microscopy and Mossbauer spectroscopy were used as complementary methods to study the structure and hyperfine interactions of the samples.
PDF
