Nanostructure in Functional Ceramics

许多陶瓷的功能特性主要由离子的位移控制，离子的位移在某些类型的氧化物的晶胞中产生微小的电偶极子。然而，为了使这些电偶极子影响块体性质，它们必须是协同的，即至少几十个单元单元的位移必须在同一方向上发生。通过改变偶极子合作的方向和长度以及偶极子发生的温度(T_C)，为特定的应用量身定做功能特性。在用作射频滤波器的陶瓷电容器中，掺杂的中尺度非均匀分布改变了偶极子的大小、方向和起始温度，防止了滤波器频率随温度的显著变化。在压电陶瓷中，单斜晶系、四方体和菱面体相的纳米级混合物，其中偶极子的方向/大小在每个结构中都不同，从而优化产生的电荷/位移。该计划旨在利用先进的分析仪器研究陶瓷的局部纳米结构，并确定其与块体性能(介电常数、介电损耗、压电性)的关系。这一认识将被用于提高性能和开发新的功能陶瓷。

The functional properties of many ceramics are controlled principally by displacements of ions which create small electric dipoles across the unit cells of certain types of oxides. However, in order for these electric dipoles to affect the bulk properties, they must be cooperative, i.e. the displacemetns must occur in the same direction for at least several tens of unit cells. Functional properties are tailored for a specific application by modifying the direction and length over which the dipoles are cooperative as well as the temperature at which they occur (Tc). In ceramic capacitors which act as rf filters, a mesoscale heterogeneous distribution of dopants modifies the magnitude, direction and onset temperature of the dipoles, preventing the filter frequency from changing significantly with temperature. In piezoelectric ceramics, a nanoscale mixture of monoclinic, tetragonal and rhombohedral phases in which the direction/magnitude of the dipoles differs in each structure, optimises the charge/displacement produced. This programme aims to investigate the local nanostructure of ceramics using advanced analystical instrumentation and determine its relation to bulk properties (permittivity, dielectric loss, piezoelectricity). This understanding will be used to improve performance and develop new functional ceramics.