Structure Determination and Compositional Modification of Body-Centered Tetragonal PX-Phase Lead Titanate

The fibrous PX-phase of lead titanate (PT), which can be synthesized by a hydrothermal method, has been studied to clarify its structural aspects on the atomic level. By combining synchrotron X-ray diffraction and electron microscope analysis with a first-principles calculation, a unique open-channel structure with a 5.529 Å diameter bore through the whole wire is determined. First-principle modeling reveals that the PX-phase structure has an indirect wide band gap and a higher formation enthalpy than the tetragonal perovskite phase. Both the frequency and symmetry of Raman-active lattice vibrational modes have been identified with polarized Raman spectra on individual monocrystalline PX-phase PT wires, showing a good match with the first-principles calculation. Furthermore, the doping of Zr in the PX-phase PT and the influence on the structure were investigated, showing a limit of 17% incorporation of Zr in the PX-phase PT.本研究针对可通过水热法制备的纤维状钛酸铅（PT，lead titanate）PX相展开探究，旨在阐明其原子尺度下的结构特性。通过结合同步辐射X射线衍射（synchrotron X-ray diffraction）、电子显微镜分析（electron microscope analysis）与第一性原理计算（first-principles calculation），本研究确定了一种独特的开放通道结构：该结构沿整根纤维丝分布有直径为5.529 Å的孔洞。第一性原理建模（first-principle modeling）结果显示，PX相结构具备间接宽禁带特性，且其生成焓（formation enthalpy）高于四方钙钛矿相（tetragonal perovskite phase）。通过对单根单晶（monocrystalline）PX相PT纤维丝开展偏振拉曼光谱（polarized Raman spectra）测试，本研究确定了拉曼活性晶格振动模式（Raman-active lattice vibrational modes）的频率与对称性，该结果与第一性原理计算结果吻合良好。此外，本研究还探究了PX相PT中的锆（Zr）掺杂行为及其对结构的影响，结果表明PX相PT中锆的最大掺入量为17%。