Solid State Growth of Piezoelectric Single Crystals

其目的是采用固态工艺而不是传统的熔融生长（布里奇曼）路线来生长压电材料的单晶。后者具有由熔体和固体之间的元素分配引起的组成梯度的固有缺点。在高温下，晶种通过消除晶界而在多晶体中生长的固态途径。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。该项目将集中于Pb（Mg 1/3 Nb 2/3）O3 -PbTiO 3-PbZrO 3钙钛矿晶体，并将探索使用热压制备细晶粒、无孔的多晶前体。这也具有包含任何挥发性阳离子的损失的优点。晶体生长步骤的退火条件的选择将基于对材料中导致晶种界面处优先晶粒生长的扩散过程的研究。将使用电子显微镜和X射线衍射表征所得晶体的化学和物理均匀性。压电和介电性能将与布里奇曼路线生长的类似组合物进行比较。

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.