Visualization of Douphine Twin in Quartz Filter by Electron Acoustic Microscopy
Douphine twin (DT) is a main structural defect of piezoelectric quartz crystals1. DT is a quartz crystal region where electric x and mechanical y axes are rotated 180° about optical axis z relative to their direction in matrix. The DTs occur as a rule in producing quartz components under thermal and mechanical treatment of the starting material. If the quartz plate bulk consists of about 50% of DTs, it is impossible to excite piezo-vibrations1. Smaller content of DTs results in irreproducible electrical characteristics of quartz components. Twinned quartz is optically homogeneous, so DTs can not be revealed by direct optical methods. The wide-spread method, which is used for this purpose, is chemical etching in aqueous solution of HF, but it is a destructive one. DTs could also be revealed by the Laue patterns or using piezo or electro-optic effects2,3. Direct visualization of DTs at microscopic level can be achieved by scanning acoustic microscopy4 which is nondestructive technique and, besides, gives the information about the local surface acoustic wave velocities. However, the use of acoustic microscopy requires good polishing of the sample surface.
KeywordsElastic Constant Quartz Filter Laue Pattern Piezoelectric Quartz Crystals1 Good Polishing
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