Bi2Ti2O7: It Is Not What You Have Read
Bi2Ti2O7: It Is Not What You Have Read
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DOI：
10.1021/cm202154c
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发表时间：
2011-11-22
影响因子：
8.6
通讯作者：
Nino, Juan C.
中科院分区：
文献类型：
--
作者：
Esquivel-Elizondo, J. Roberto;Hinojosa, Beverly Brooks;Nino, Juan C.
采用共沉淀法制备了纯Bi 2 Ti 2 O 7多晶陶瓷颗粒，并采用微波烧结技术制备了致密相纯Bi 2 Ti 2 O 7多晶陶瓷颗粒。在粉末或颗粒中没有发现第二相的证据。这一首次成就允许这种陶瓷化合物的主要热物理，晶体学和介电特性。采用密度泛函理论对烧绿石的结构进行了模拟，并通过理论计算得到了烧绿石的X射线衍射图谱，从而确定了实验化合物的纯度。文献中关于这种材料的结构，稳定性和假定的铁电性的报道之间的分歧进行了讨论和澄清。根据目前的研究结果，提出了一个修改的Bi 2 O3-TiO 2系统的相图。此外，与先前的报道相反，Bi 2 Ti 2 O 7的介电特性揭示了在室温下具有高介电常数值（在500 kHz下为115）的线性电介质，并且更值得注意的是，温度和频率相关的介电弛豫。
Coprecipitation synthesis methods followed by microwave sintering techniques were utilized to obtain dense phase pure Bi2Ti2O7 polycrystalline ceramic pellets. No evidence of secondary phases was found in the powder or pellets. This maiden achievement allowed for primary thermophysical, crystallographic, and dielectric characterization of this ceramic compound. Density functional theory was used to model the structure of the pyrochlore, from which the theoretical X-ray diffraction pattern was obtained to determine the purity of the experimental compound. Discrepancies among reports in literature regarding the structure, stability, and supposed ferroelectricity of this material are discussed and clarified. A modification to the phase diagram of the Bi2O3-TiO2 system is proposed based on the results of the present investigation. In addition, and contrary to prior reports, the dielectric characterization of Bi2Ti2O7 reveals a linear dielectric with high permittivity values at room temperature (115 at 500 kHz), and more remarkably, a temperature and frequency dependent dielectric relaxation.