Structural and magnetic properties of Sm2Fe17−xCrxC2 nanocrystalline carbides with 0≤x≤2

The crystallographic and the Curie temperature of the Sm₂Fe_17−xCr_xC₂ (x=0.5, 1, 1.5 and 2) carbides have been extensively studied. X-ray diffraction studies have shown that all these alloys are approximately single phases corresponding to the Th₂Zn₁₇ type rhombohedral structure with a small amount of -Fe. The amount of this residual -Fe phase decreases with increasing the Cr atomic content. It decreases from 1 wt% for x=0.5 to 0.4 wt.% for x=2. The lattice parameter c increases as a function of the Cr atomic content x from x=0 to x=1.5 and then decreases. This is due to the Cr atoms which prefer to substitute the Fe atoms in the 6c sites located along the c-axis. The lattice parameter a and the unit-cell volume decrease in all substitution ranges. The insertion of the C atoms leads essentially to an increase of the distances between the 9d and 18h sites and the 9d–18f sites. The Curie temperature reaches a maximum value of 583 K for x=1.5 and then decreases to 551 K for x=2. The enhancement of the T_c for lower Cr contents is due to a lowering of the hybridization of the iron atoms with their neighbors, the magnetovolume effect and the reduction of antiferromagnetic interactions. However, the decrease in T_c for higher Cr content is due to the reduction in the number of Fe–Fe pairs due to the magnetic dilution effect. For given interatomic distances, the exchange coupling of the Cr–Cr atoms is not of antiferromagnetic type and the exchange integral of the Cr–Cr pair is higher than that of the Fe–Fe pair.     

Influence of Si substitution on magnetic properties,random anisotropy,and magnetocaloric effect of nanocrystalline Sm2Fe17−xSix

Journal of Materials Science: Materials in Electronics - Nanocrystalline iron-rich intermetallic compounds Sm2Fe17?xSix ( $$x = 0, 1, 1.5, 2$$ ) were studied by means of X-ray diffraction...     

Silicon gettering: Some novel strategies for performance improvements of silicon solar cells

This paper reports the recent performance improvements in crystalline silicon solar cells. These have been achieved by a combination of two mechanisms. One is related to the solar cell design which consists of grooving silicon substrates to obtain a structure suitable to perform an efficient gettering process. The proposed structure consists of buried emitter contacts rear locally diffused. Chemical-vapour etching has been used in the process sequence both to realize buried contacts and opening periodic arrangement of small deep grooving holes, for local aluminum diffusion. The second consists to perform a gettering sequence by Rapid Thermal (RT) heat treatments of p-type silicon in an infrared furnace, in controlled silicon tetrachloride (SiCl₄) and N₂ gas atmosphere. The resulting silicon shows an increase of minority drift mobility determined by Hall Effect to reach 1417 cm² V^{− 1} s^{− 1}, and a decrease in resistivity over 40 μ m on both sides of silicon substrates. Moreover, Light Beam Induced Current (LBIC) investigations show an improvement of diffusion bulk lengths (L_n) to ward 210 μ m as compared to silicon starting substrates.