Single crystalline piezoelectric materials such as LiTaO3 and LiNbO3 have become vital components in achieving higher data transfer rates in mobile communications. These materials serve as substrates for precise and efficient frequency filters, playing an integral role in the latest 5G mobile communication network standards. Typically, crystal growth in specific orientations is pursued to ensure optimized functional properties. However, it is essential to assess whether these orientations can withstand thermo-mechanical loading during qualification and in service.
This study investigated the mechanical performance of LiTaO3 and LiNbO3 single crystals components with different surface qualities through fracture experiments conducted at various length scales and loading scenarios. The experimental results unveiled significant differences in strength between LiTaO3 and LiNbO3, even when subjected to the same surface finishing. Moreover, the grinding and polishing direction with respect to cleavage planes exhibited a substantial influence on the mechanical performance. Fractography played a key role in identifying these cleavage planes, providing insights into variations in fracture patterns between the two materials and shedding light on the (sub-) surface damage introduced during the polishing processes. These findings have the potential to guide the fabrication of LiTaO3 and LiNbO3 materials with specific orientations, resulting in optimized structural and functional properties.