کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
9784008 | 1512027 | 2005 | 8 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Heterovalent cation-substituted Aurivillius phases, Bi2SrNaNb2TaO12 and Bi2Sr2Nb3âxMxO12 (MÂ =Â Zr, Hf, Fe, Zn)
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
مهندسی مواد
مواد الکترونیکی، نوری و مغناطیسی
پیش نمایش صفحه اول مقاله
چکیده انگلیسی
We describe the synthesis and structural characterization of new aliovalent cation-substituted n = 3 Aurivillius phases of the formulas, Bi2SrNaNb2TaO12 (I), Bi2Sr2Nb2ZrO12 (II), Bi2Sr2Nb2.5Fe0.5O12 (III) and Bi2Sr2Nb2.67Zn0.33O12 (IV). Energy dispersive X-ray (EDX) investigation of the chemical compositions showed that while cation-stoichiometric materials are formed for I and II, single-phase materials are obtained only for the compositions given for III and IV suggesting that the compositions tend to be oxygen-stoichiometric. The results show that aliovalent cation-substituted n = 3 Aurivillius phases similar to Bi2Sr2Nb2MIVO12 (M = Ti, Mn) exist for several metal cations, viz., TaV, ZrIV, FeIII and ZnII. Refinement of the crystal structures from the powder X-ray diffraction (XRD) data for I and III revealed that bismuth is essentially confined to the Bi2O2 layers and the aliovalent cation shows a preference for the middle perovskite sheet. The present work is significant for two reasons: firstly, the presence of cations such as Sr2+, Na+ (that do not contain lone pair s2 electrons) in the perovskite slabs seems to render the structure centrosymmetric; secondly, a preferential/partial ordering of octahedral site cations in the perovskite slabs obtains in these materials, that seems to be dictated by a second order Jahn-Teller effect associated with d0 cations.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Materials Science and Engineering: B - Volume 121, Issues 1â2, 25 July 2005, Pages 112-119
Journal: Materials Science and Engineering: B - Volume 121, Issues 1â2, 25 July 2005, Pages 112-119
نویسندگان
T.K. Mandal, T. Sivakumar, S. Augustine, J. Gopalakrishnan,