The Boron-Rich Phase and Its Behaviour in Nd-Fe-B Magnet
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摘要: 本文利用1000kV超高壓電鏡、穆斯堡爾譜儀、X射線衍射儀和磁測量儀等對Nd-Fe-B永磁合金中的富硼相進行了研究。結果表明:富硼相以1個孤立的相存在于Nd-Fe-B永磁合金中,它一般位于基體相Nd2Fe14B的三角晶界處,占據的體積份數為4.6%,富硼相中有高密度的缺陷存在,這些缺陷的方向垂直于$\vec C$軸。
富硼相的化學式可以寫為Nd1+εFe4B4(s≈0.1),該化合物由2套亞結構,即Fe-B亞結構和Nd亞結構相互套穿而成。2個亞結構均具有四方對稱,在四方基面上的晶格常數相同,但沿$\vec C$方向卻有不同的周期,所以富硼相可能為一維的成分變化型無公度結構。在室溫下富硼相呈順磁性,能夠在磁體中釘扎疇壁而提高矯頑力,富硼相的顯微結構和溫度有關,由矯頑力對溫度的依賴關系和電鏡觀察表明富硼相對疇壁的釘扎可能屬于強釘扎。Abstract: The boron-rich phase in Nd-Fe-B magnet was studied by means of HVEM, Mossbauer spectroscopy, X-ray diffraction and magnetic measurements. The chemical formula of the boron-rich phase can be represented by Nd1+εFe4B4. It is composed of two interpenetrating substructures, both have tetragonal symmetry. Since two substructures have different periods in $\vec C$ direction, the boron-rich phase may belong to the compositional incommensurate structure in one dimension. It is paramagnetic at room temperature and may behave as the pinning sites in the magnet. The observation results by HVEM of micrOstructure of Nd-Fe-B alloy at different temperature are also given. The coercivity mechanism is discussed coupling with the reported results. -
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