铅基复合钙钛矿型弛豫铁电单晶的生长基元与生长机理Ⅰ.PMNT单晶的表面形貌、负晶结构及生长基元的组装与拆分  

Growth Units and Growth Mechanism of Lead - Based Complex Perovskite Relaxor Ferroelectric Single Crystals I .The Surface Morphology, Negative Crystal Structure and Assembling or Unlinking of Growth Units in PMNT Crystals

作　　者：许桂生[1,1] 许桂生[1,1] 罗豪甦[1] 仲维卓[1] 殷之文[1] 刘克 

机构地区：[1]中国科学院无机功能材料开放实验室

出　　处：《化学学报》2000年第2期172-177,共6页Acta Chimica Sinica

基　　金：国家自然科学基金(59995520)重大项目;中国科学院重大项目;上海市重点项目资助

摘　　要：铅基复合钙钛矿型弛豫铁电单晶体PMNT的生长基元为多种[BO_6]配位八面体,晶体生长过程可视为多种八面体基元与Pb^(2+)的组装过程.这些生长基元向{111}面叠合时易采取法向生长机制,向{001}面叠合时易采取层状生长机制,由此决定了晶体生长速度的各向异性与晶体的形貌.Bridgman法生长的PMNT晶体在生长过程中由内向生长机制形成规则的负晶结构;在晶体生长过程中,在其自然表面上可形成正形与负形两种形貌;在高温退火过程中,由于PbO的分解,晶体表面上可形成类似“蚀象”的构型,这些可从[BO_6]八面体生长基元的组装或拆分方面获得解释.This paper discusses the relation between the surface morphologies and negative crystal structures as well as the assembling or unlinking of growth units in PMNT crystals. The growth units in relaxor ferroelectric single crystals PMNT and PZNT, which belong to lead - based complex perovskite structures, are considered as coordination octahedra [ BO6 ] and the growth process as the assembling of these units. These crystals are formed via a normal growth mechanism when their units grow on the {111} faces. However, the layer - by -layer growth mechanism is in operation when the units grow on {001} faces. This decides the anisotropy of growth rates and the crystal morphologies. The negative crystal structures of the PMNT single crystals with regular facets grown by the Bridgman technique could occur when the crystals grew from the melt surrounded by frozen crystals. The special surface morphologies, including positive and negative ones, could form during the period of crystal growth. Furthermore, a regular negative configuration on the surface of crystal plates as if beingetched, could stem from the decomposition of PbO after annealing at high temperature. All of these phenomena could be rationalized by the mechanism of the assembling and unlinking of the [ BO6 ] octahedral growth units.

关 键 词：弛豫铁电体 PMNT 晶体生长 生长基元 

分 类 号：O78[理学—晶体学]