Application of mechanical activation in synthesizing multiferroic Pb(Fe1/2Nb1/2)O3 powders

In the study, the method of high-energy powder milling – mechanical activation (MA) was used for synthesizing Pb(Fe1/2Nb1/2)O3 (PFN) powders. For the purpose of comparing the influence of high-energy milling on PFN synthesis, two groups of powder samples were used. The first mixture consisting of simple oxide powders; the second one consisting of compound oxide powders. The obtained powders were subjected to structural analysis with the use of XRD and Mossbauer spectroscopy. Tests revealed that during the process of high-energy milling of initial constituents a partial synthesis of PFN material phases occurs. By comparing the two methods of PFN synthesizing it may be stated that mechanical activation in the case of a simple oxide mixture (PFN1) is equally effective as for a compound oxide mixture (PFN2).[1] Y. X u, Ferroelectric materials and their applications. North – Holland, Amsterdam 1991. [2] S.L. S w a r t z, V.E. W o o d, Condensed Matter News 1, 4-14 (1992)[3] E.G. F e s e n k o, A.Ya. D a n c i g e r, O.N. R a z u -m o v s k a y a, Novye piezokeramicheskie materialy, RGU, Rostov-na-Donu, 1983. [4] O. R a y m o n d, R. F o n t, N. S u a r e z, J. P o r -t a l l e s, J. M. S i q u e i r o s, Ferroelectrics 294, 141 (2003). [5] K. S i n g h, S.A. B a n d, W.K. K i n g e, Ferroelectrics 306, 179 (2004). [6] X. G a o, J. X u e, J. W a n g, Journal of the American Ceramic Society 85, 565 (2002). [7] D. B o c h e n e k, Z. S u r o w i a k, Journal of Alloys and Compounds 480, 732-736 (2009). [8] D. B o c h e n e k, J. D u d e k, The European Physical Journal – Special Topics 154, 1 19-22 (2008). [9] D. B o c h e n e k, R. Z a c h a r i a s z, Archives of Metallurgy and Materials, 54, 903-910 (2009). [10] D. B o c h e n e k, Journal of Alloys and Compounds 504, 508-513 (2010). [11] B.D. S t o j a n o v i c, A.Z. S i m o e s, C.O. P a i -v a - S a n t o s, C. J o v a l e k i c, V.V. M i t i c, J.A. V a r e l a, Journal of the European Ceramic Society 25, 1985-1989 (2005). [12] J.S. B e n j a m i n, Scientific American 234, 40-43 (1976). [13] A.S. K h i m, X. J u n m i n, J. W a n g, Journal of Alloys and Compounds 343, 156-163 (2002). [14] X.S. G a o, J.M. X u e, T. Y u, Z.X. S h e n, J. W a n g, Materials Chemistry and Physics 75, 211-215 (2002). [15] J. W a n g, D.M. W a n, J.M. X u e, W.B. N g, Singapore Patent 9801566-2, 1998. [16] J. W a n g, D.M. W a n, J.M. X u e, W.B. N g, Journal of the American Ceramic Society 82, 477 (1999). [17] D. D e r c z, J. D e r c z, K. P r u s i k, A. H a n c, L. P a j ą k, J. I l c z u k, Archives of Metallurgy and Materials, 54, 741-745 (2009). [18] L.B. K o n g, J. M a, H.T. H u a n g, W. Z h u, O.K. T a n, Materials Letters 50, 129-133 (2001). [19] D. B o c h e n e k, Z. S u r o w i a k, J. K r o k - K o w a l -s k i, J. P o l t i e r o v a - V e j p r a v o v a, Journal of Electroceramics 25, 122-129 (2010). [20] Y. Y a n g, H.B. H u a n g, J.-M. L i u, Z.G. L i u, Ferroelectrics 280, 75-82 (2002)

Search for canted spin arrangement in Er2−xTbxFe14BEr_{2-x}Tb_{x}Fe_{14}B with Mössbauer spectroscopy

The materials studied were polycrystalline compounds E$r_{2-x}Tb_{x}Fe_{14}B$ (x = 0.1, 0.2, 0.3, 0.4) which crystallize in a tetragonal lattice and display a variety of spin arrangements. The compounds have been measured with $^{57}Fe$ Mössbauer spectroscopy over the temperature range 80–320 K in order to investigate the spin reorientation processes. Each compound was studied in a wide temperature range, with precise Mössbauer scanning in the vicinity of the transition. The set of spectra obtained for a given compound was analyzed using simultaneous fi tting procedure to investigate the infl uence of the transition on the shape of the spectra. The fitting program was specifi ed to analyze the transition according to the ‘two state model’: spins fl ip abruptly from initial angle to fi nal arrangement ($90^{\circ} angle$ ). Obtained results suggest that spin reorientation process cannot be described using only the mentioned above model. Additional computer simulations based on the Yamada–Kato model were conducted to determine temperature range and the type of spin alignments in the vicinity of the transition. These theoretical results supported by spectra analysis suggest the existence of intermediate (canted) spin arrangements in the studied compounds. The spin arrangement diagram was constructed

Spin reorientation process in Tm_{2–x}Ho_{x}Fe_{14}B : analysis of conical arrangement based on Mössbauer spectra

The spin reorientation process in the Tm2–xHoxFe14B series of compounds was studied using 57Fe Mössbauer spectroscopy over the temperature range 5.2–320 K with a focus on the analysis of conical spin arrangement. Each compound was studied by precise Mössbauer scanning in the vicinity of the transition and during the transition. By applying computer simulations based on the simplified Yamada-Kato model, as well as on some literature data for R2Fe14B (R = Tm, Ho) compounds, the above series was selected for studies as it contains compounds with different spin arrangements (axial, planar, conical). It was a crucial requirement for obtaining unambiguous angular dependences when applying a simultaneous fitting procedure of Mössbauer spectra. Such an extended procedure was applied which allowed the temperature dependence of the angle describing the position of the magnetization vector to be obtained. The results were compared with those from theoretical simulations. The spin arrangement diagram was constructed. A conical spin arrangement was confirmed over a wide temperature range

Influence of Aluminium and Silicon Content on the Phase Composition, Microstructure and Magnetic and Mechanical Properties of Multicomponent FeNiCoAlSi Alloys

This work deals with the characterization of structure, magnetic and mechanical properties of (FeNiCo)100-x(AlSi)x (x = 0, 5, 10, 15, 25) multicomponent alloys prepared by casting. The results of X-ray diffraction measurements, scanning electron microscopy observations and hardness and magnetic properties investigations are presented. The studies show that cast (FeNiCo)100-x(AlSi)x alloys reveal dendritic morphology and their phase composition depends on (Al + Si) content. For x ≤ 10 a face-centered cubic phase is observed, while the increase of Al and Si content results in a body-centered cubic phase formation. It leads to a fivefold increase of hardness from 88 HV to 526 HV. The investigated alloys have high magnetic induction reaching 170 emu/g, while their coercivity value is even up to 2.9 kA/m for x = 15, and strongly depends on chemical and phase composition

Crystallization of Fe-B Metallic Glasses

score: 8collation: 131-13

Influence of Sn Addition on the Amorphization and Thermal Stability of CuTiZrNi Powders Processed by Mechanical Alloying

score: 0collation: 917-92

Effects of Solidification Conditions on Microstructure and Properties of High-Entropy Alloys from the CoCrFeMnNi Family

International audienceAlloys from the CoCrFeMnNi family remain the most studied austenitic high-entropy alloys. In this study, four alloys, i.e., Cantor alloy, A3S (modified nonequiatomic Cantor composition), both “pure” or doped with carbon (200 wt. ppm) and niobium (1.3 wt.%), were investigated. Firstly, alloys were induction cast using a cold-crucible method. The obtained ingots were molten, and rapidly solidified by melt-spinning at two cooling rates to obtain “ribbons”, typical of such processing. The effects of the solidification rate and the presence of carbon and niobium on the microstructure and hardness were studied. All the studied alloys show an fcc structure. The lattice parameter of the fcc phase increases with the increasing cooling rate, and with the addition of niobium and carbon, which confirms at least a partial presence of these elements in solid solution. Yet, TEM observations revealed the formation of nanometric NbC precipitates. The microstructure of melt-spun ribbons consists of equiaxed grains of a few micrometers in size. The higher cooling rate led to a small decrease in the grain size and a slight increase in hardness. Moreover, the hardness of doped alloys can be further improved by annealing (500°C for 24 h) through NbC precipitation

Evaluation of Harmonic Structure Obtained in Mechanically Milled Powders and Pulse Plasma Sintered Compacts of Austenitic Steel

The paper describes an attempt to obtain harmonic structure (HS) in AISI308L steel. Harmonic structure is the term related to the microstructure fabricated by mechanical milling of metallic powders under soft milling conditions, resulting in the formation of plastically deformed, grain-refined shell and unchanged core. This microstructure can be preserved after successful powder compaction. The powders of AISI308L steel were milled under soft condition up to 50 h and then compacted by pulse plasma sintering at 900–1100 °C. For powders and compacts XRD, SEM and hardness measurements were applied as characterization techniques. The milling process resulted in austenite transformation into nanocrystalline ferrite and formation of grain refined outer layer. The applied pulse plasma sintering parameters allowed preservation of this microstructure and manufacturing of compacts with homogeneous distribution of elements, relative density above 95% and hardness in the range 167–185 HV, depending on sintering temperature. Simultaneously, the starting phase composition was restored, i.e., austenite with 12% contribution of ferrite. The crystallite size of austenite was about 20 nm and was significantly smaller then in starting powders

Ball Miling of Co-Fe-Si-B Alloys

score: 0collation: 297-30