极地还是非极地? 在A2Ti(IO3) 6中A+阴离子极性控制 (A = Li,Na,K,Rb,Cs,Tl)
Hong-Young Chang1, Sang-Hwan Kim, Kang Min Ok
1Department of Chemistry, University of Houston, 136 Fleming Building, Houston, Texas 77204-5003, USA.
Journal of the American Chemical Society
|April 24, 2009
概括
合成了新的金属酸,Li和Na相表现出非中心对称 (NCS) 极性质,而K,Rb,Cs和Tl类似物是中心对称 (CS) 和非极性. 这种转变是由离子大小和结构因素解释的.
科学领域:
- 固态化学 固态化学
- 无机材料科学 是一种无机材料科学.
- 晶体学 晶体学是指结晶学.
背景情况:
- 探索具有有趣结构和电子特性的新材料对于推进材料科学至关重要.
- 金属和 (I) 酸代表了一类化合物,在非线性光学和铁电学中具有潜在的应用.
- 了解晶体结构,阴离子大小和物理性质之间的关系是设计新功能材料的关键.
研究的目的:
- 为了合成和表征一系列新的金属或 (I) 酸,A (II) Ti (II) IO (III) (3) (VI) (6).
- 研究这些化合物的结构和极性质,并解释从非中心对称 (NCS) 极相过渡到中心对称 (CS) 非极相.
- 探索这些材料中铁电和其它物理性能的潜力.
主要方法:
- 合成了六种新的酸化合物:Li(2)Ti(IO(3)) ((6),Na(2)Ti(IO(3)) ((6),K(2)Ti(IO(3)) ((6),Rb(2)Ti(IO(3)) ((6),Cs(2)Ti(IO(3)) ((6),Tl(2)Ti(IO(3)) ((6).
- 使用X射线衍射进行结构性表征,包括空间组和格子参数的确定.
- 电子结构分析,红外光谱,紫外光谱,热重力测量分析和离子交换反应.
- 对极性材料进行第二子生成,压电和极化测量.
主要成果:
- 发现酸的Li和Na相是非中心对称的 (NCS) 和极性的.
- 确定K,Rb,Cs和Tl类似物是中心对称 (CS) 和非极性.
- 从NCS极性结构到CS非极性结构的观察过渡被成功地用阴子大小参数,协调要求和键值概念解释.
- 对于Na2Ti和IO3的计算表明,极化逆转在能量方面是不利的,这证实了它的极性,但不是铁电性质.
结论:
- 一系列具有不同极性质的六种金属或Tl(+) 酸已经成功合成和特征化.
- 离子体大小在确定这些酸的中心对称或非中心对称性方面起着至关重要的作用.
- 虽然极性,但研究的材料,如Na(2) Ti(IO(3)) ((6),由于不利的极化反转能量,它们不是铁电.
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