Synthesis and characterization of nanoscaled Ba(Ti1-x-ySnxGey)O3 powders and corresponding ceramics

Nanoscaled Ba(Ti1−x−ySnxGey)O3 (BTSG − x − y, x = 0–0.1, y = 0–0.05) powders were synthesized by a sol–gel method (SG) and, as a reference, coarse powders by a mixed-oxide method (MO). The particle sizes were determined by XRD, BET, photon correlation spectroscopy (PCS) and scanning electron microscopy (SEM). The sol–gel method supplied globular particles with narrow fractions in the range between 53 nm and 125 nm. However, from the mixed-oxide method irregularly grown particles were generated with diameters between 300 nm and 700 nm. The SG powders showed a higher sintering activity and, additionally, Sn4+ ions were incorporated at lower temperatures into the BaTiO3 structure. The addition of at least 2 mol% BaGeO3 (BG) resulted in ceramics of densities as high as 96% even at 1050 °C. Furthermore, the cubic ⇆ tetragonal phase transition temperatures were measured by dilatometry, differential thermal analysis (DTA) and dielectric measurements. The temperature and sharpness of the transition are dependent on tin and germanium content. Increasing tin and germanium concentration causes the phase transition temperature to decrease and more diffuse transition.

О вычислении температуры Дебая и температуры фазового перехода кристалл-жидкость для бинарного сплава замещения

A method of estimating the interatomic pair interaction potential parameters for a binary substitution alloy with consideration for the deviation of its lattice parameter from the Vegard law is proposed. This method is used as a basis to calculate the Debye temperature and Grüneisen parameters of a SiGe alloy. It is shown that all these function nonlinearly variate with a change in the germanium concentration. Based on this technique and Lindemann's melting criterion, a method for calculating the liquidus and solidus temperatures of a disordered substitution alloy is proposed. The method is tested on the SiGe alloy and demonstrates good agreement with experimental data. It is shown that when the size of a nanocrystal of a solid substitution solution decreases, the difference between the liquidus and solidus temperatures decreases the more, the more noticeably the nanocrystal shape is deflected from the most energetically optimal shape.

Negative Air Ion Release and Far Infrared Emission Properties of Polyethylene terephthalate/Germanium Composite Fiber

PET/germanium composite fibers that with negative air ion release and far infrared emission properties were prepared by adding germanium particles to polyethylene terephthalate (PET) and melt-spinning. The morphology, effect of the germanium content on the negative air ion release, far infrared emission, thermal and mechanical properties of the fibers were investigated. The germanium particles uniformly disperse in the PET fibers when the concentration ranged from 1% to 3 percent. The value of the negative air ions released by the PET/germanium composite fibers increased with increasing content of germanium and reached 1470 ions/cm-3 at 3% germanium concentration. The highest far infrared normal emissivity (0.9) was obtained at 3% germanium concentration. The TG and DSC analysis revealed that the two heat histories used had little effect on the PET. The crystallinity of the composite fibers decreased with increasing germanium content. Water fastness testing showed that the PET/germanium composite fibers had excellent and durable negative air ion release and far infrared emission properties. The breaking strength of the fibers decreased with increasing of the germanium content.

Structure and magnetism of the solid solution GexFe4−xNy (0 ≤ x ≤ 1): from a ferromagnet to a spin glass

The experimental and theoretical study of the solid solution GexFe4−xNy (0 ≤ x ≤ 1) reveals a structural transition from the cubic to the tetragonal system as well as a magnetic transition from a ferromagnet to a spin glass accompanying the increasing germanium concentration.