Solid State Growth of Piezoelectric Single Crystals

其目的是采用固态工艺而不是传统的熔体生长（Bridgman）方法来生长压电材料的单晶。后者具有固有的缺点，即由熔体和固体之间的元素分配引起的成分梯度。种子晶体在高温下通过消除晶界而在多晶体中传播的固态途径。固态晶体生长（SSCG）排除了这种分配梯度，也避免了与使用铂坩埚相关的高成本。该项目将重点研究Pb(Mg1/3Nb2/3)O3 - PbTiO3 - PbZrO3钙钛矿晶体，并将探索使用热压法制备细粒、无孔、多晶前驱体。这也有包含任何挥发性阳离子损失的优点。晶体生长步骤的退火条件的选择将基于对材料中导致种子界面优先晶粒生长的扩散过程的研究。所得晶体将用电子显微镜和x射线衍射进行化学和物理均匀性表征。压电和介电性能将与通过布里奇曼路径生长的类似成分进行比较。

The aim is to grow single crystals of piezoelectric materials employing a solid-state process rather than the conventional melt-growth (Bridgman) route. The latter has inherent disadvantage of composition gradients resulting from partitioning of elements between the melt and the solid. The solid state route in which a seed crystal is propagated through a polycrystalline body by elimination of grain boundaries at high temperature. Solid state crystal growth (SSCG) precludes such partitioning gradients and also avoids the high cost associated with the use of platinum crucibles.The project will focus on crystals of the Pb(Mg1/3Nb2/3)O3 - PbTiO3 - PbZrO3 perovskite and will explore the use of hot-pressing to prepare fine-grained, pore-free, polycrystalline precursors. This also has the advantage of containing the loss of any volatile cations. Selection of annealing conditions for the crystal growth step will be based on investigations of the diffusion processes in the material that result in preferential grain growth at a seed interface.The resulting crystals will be characterized for chemical and physical uniformity using electron microscopy and X-ray diffraction. Piezoelectric and dielectric properties will be compared with similar compositions grown by the Bridgman route.