主讲：邢献然

时间：2018年5月11日10:00

地点：会议中心第三报告厅

主办：材料学院

报告内容：Materials that exhibit negative thermal expansion (NTE) are rare owing to the rigorous requirements for NTE formations. NTE induced by a combination of two or more effects is exceedingly unusual, but is highly desirable to be utilized to understand the mechanism of NTE. In this work we show the introduction of lithium could achieve the volumetric NTE in a tetragonal tungsten bronze (TTB) oxide, Pb_2.15Li_0.7Nb₅O₁₅ (PPLN), that was caused by the synergistic ferroelectric origin and structural flexibility. Moreover, the hidden lithium is artfully revealed by a combination of X-ray and neutron diffraction, which are found to be located in the quadrangular (A1) tunnel sites of the TTB framework, and mixed with lead in a ratio that causes the total neutron scattering to be nearly zero. Furthermore, the giant SHG effect in PPLN has been observed, which originates from the huge local polarization. The present compound provides a good example to further investigate the possible mechanism of the NTE materials.

主讲简介：邢献然，北京科技大学教授。1988年7月在安庆师范学院获化学专业学士学位，1994年3月在北京科技大学获冶金物理化学专业博士学位。2001至2017年任物理化学系主任，现任国务院学位委员会冶金工程学科评议组成员（召集人），教育部创新团队负责人，英国皇家化学会会士（FRSC）、Inorg.Chem.Frontiers期刊编委、Chemical Communications顾问编委、《中国稀土学报》（中、英文版）编委等。研究方向：①负热膨胀化合物的设计与性能调控，②固体结构（晶体结构和局域结构）与新型功能化合物的合成，③冶金过程物相演变和反应机理等；主讲课程："固体化学"、"材料化学"、"冶金热力学"、"相图在冶金中的应用"、"冶金和材料热力学"、"功能材料"等10余门课程。在J. Am. Chem. Soc.、Phys. Rev. Lett.、Nature Comm.等杂志发表论文200余篇，获省部级科技奖励4项，授权国家发明专利15件，培养全国百篇优秀博士学位论文获得者1名、北京市优秀博士学位论文获得者2名。