溶胶--凝胶法制备的Zn1-xCoxO晶体粉末的结构和磁性行为

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滃 ÑÍÈ 200822208 ÃÅ ÑÍÈ 1091139–9–00 ƶ : 2010–10–12, °¶ : 2010–12–07 Ù Ú« : ´ Ü, Æ, 1963 ¥Æ, ÞË, ¶ Æ
DOI: 10.3724/SP.J.1037.2010.00541
338
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is their intrinsic attribute, in which the Zn0.98 Co0.02 O sample sintered at 500 and 700 has the highest coercivity (Hc ) of 334.02 Gs and the highest remanent magnetization ratio (Mr /Ms ) of 0.1813, respectively, and the Zn0.96 Co0.04 O sample sintered at 950 has the maximum magnetic energy product (BH) of 1.7604×10−4 J/kg and saturation magnetization (Ms ) of 0.5583 Am2 /kg. The magnetic behaviors of these samples vary not only with the concentration of Co, but also with the size of crystal grains and the concentration of oxygen vacancies. It can be found that the moderate Co content and the larger size of crystal grains are in favour of increasing room–temperature ferromagnetic characteristics. Meanwhile, as far as the same concentration of Co is concerned, the smaller volume of the cell contributes to increase room–temperature ferromagnetism. KEY WORDS sol–gel technique, Zn1−x Cox O, room temperature ferromagnetism
ZnO
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×) Â Ò Ã ³ ÉÎ× Ì £° 99.99% Ò ¬ÙªÝ℄ (Zn(CH CO)·2H O) ÄÛÙªÝ (Co(CH CO)·4H O), µ Ý ª 0.8 mol/L ½Ù ª Ë ℄. Ö 1.6 mol/L Ò ª Ë« Ú°» Þ Ð, Î 60 ¨ Ù², È· ­ 2 h. Ý ­ Ê Ò Î 48 h Î, Ù© ± Ê Ò ´ ¥ Þ Å £ Ò Í© . ÝÍ© Ö¿Ì 220 ¨, À­ ²© , ݲ © ªËĺ Ù℄ ´ £ £ £À² ÚÛ ¸ Þ. · ÉÒ ¸ Þ ³ , ·£ ³ ° 500, 600, 700, 800, 900 Ä 950 ¨, ·Ï×° 2 h. °Ì , Ý S À, x ² É, T ² ·£ (¨). Ò¨ ³¾ X ÀÁÜÀ¨ (XRD, CuK , X’pert High Scoreplus) Ä H–600 ÀÜ (TEM) Ù Ä ; Ò Ä JCM– 5400 Ô Ü (SEM) Ä£ ¨ (EDS) ² Â; ¶
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STRUCTURE AND MAGNETIC BEHAVIOR OF Zn1−xCox O CRYSTAL POWDERS PREPARED BY SOL–GEL TECHNIQUE
GAO Qian, SUN Benzhe, QI Yang, QI Lianzhong
College of Sciences, Northeastern University, Shenyang 110819 Correspondent: QI Yang, professor, Tel: (024)83683674,
Manuscript received 2010–10–12, in revised form 2010–12–07
ABSTRACT ZnO–based diluted magnetic semiconductors (DMSs) have been considered as one of the promising candidates for fabricating DMSs due to their initial prediction in theory of having the Curie temperature greater than room temperature, its high solubility for transition metals, and its superior semiconductor properties. Recently, Co substituted ZnO DMSs were reported frequently to show ferromagnetic properties at room temperature. However, various subsequent studies do not seem to converge on the origin of room–temperature ferromagnetism. Among the controversy, Co–cluster, Co–oxides and substitutions of Co for Zn are typical viewpoints. Meanwhile, it is not completely understood how the fabricating process influence the magnetic properties of Co–doped ZnO DMS. For this purpose, relationships among Co–doping concentration, sintered temperature, microstructure and magnetic properties of ZnO need to be invesigated particularly. In this paper, Zn1−x Cox O (x=0.01, 0.02, 0.03, 0.04 and 0.05, atomic fraction) nanocrystal powders were prepared by sol–gel technique. The crystal structure, lattice parameters, morphology and composition were characterized and analyzed by XRD, TEM, SEM and EDS, respectively. The magnetic properties were examined at room temperature using a vibrating sample magnetometer (VSM). It can be found that all the samples are composed of the particles with hexagonal wurtzite structure and the sizes of the particles are about 100 nm. For all synthesized Zn1−x Cox O samples, the lattice constants are smaller than those of un–doping ZnO crystals under the condition of the same sintered temperature. It indicates Co2+ ions have substituted Zn2+ sites. All the samples exhibit room–temperature ferromagnetic characteristics, and the ferromagnetism
E-mail: qiyang@ Supported by Science Research Program of Liaoning Province (No.200822208) and Shenyang Municipal Science Research Program (No.1091139–9–00)
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2011
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Vol.47 ACTA METห้องสมุดไป่ตู้LLURGICA SINICA
No.3
Mar. 2011 pp.337–343
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½¼ Á –¨ ¯ Ë Zn Co O(x=0.01—0.05, µ Ö) Ñ ¨ Ý, Á XRD, TEM à SEM ¨ § ¢§ ¡ ¢ à ˱Áà . § ±Õ, ¹ Â℄º 100 nm Ñ ¨¾Ä× , Zn Co O Ñ · Ö¹ ± Ñ ZnO · Ö , ° ÀË ¤ ZnO § , Ô «¢ د «¢ . Î Ñ § ℄, ³ ¶ÆÎ . §Å § , ¼Ý ÆÎ »ÍÑ ÁÔ , ´ ¦ O ´ ÆÎ Ù Ñ «, Ä¢Ñ ¡ ÆË ÑÎ . ¦ – ¨ ¯, Zn Co O, ¶ÆÎ O472.5, O482.5 ¶¸£° A ¶¾¢ 0412−1961(2011)03−0337−07 ³©­