Shaped crystal growth of langasite-type piezoelectric single crystals and their physical properties

We have grown the shape-controlled langasite-type crystals by the μ-PD method. Columnar-shaped La₃Ta_0.5Ga_5.5O₁₄ (LTG), Ca₃NbGa₃Si₂O₁₄ (CNGS), Ca₃TaGa₃Si₂O₁₄ (CTGS), Sr₃NbGa₃Si₂O₁₄ (SNGS) and Sr₃TaGa₃Si₂O₁₄ (STGS) crystals were grown using the Pt-Rh crucible with a columnar die in 3 mm diameter at the bottom. All grown crystals indicated high transparency and approximately 3 mm diameter. Their chemical phases was identified as a single phase of langasite-type structure and their lattice parameters were almost same as those of crystals grown by Cz method. In the X-ray rocking curve measurements, the grown crystals indicated equivalent crystallinity to the crystal grown by Cz method. In addition, the piezoelectric constant d₁₂ of CNGS crystal was 3.98 pC/N and this value was well correlated with those of previous reports.