Shape-controlled crystal growth of Sr3NbGa3Si2O14 and Sr3TaGa3Si2O14 piezoelectric single crystal by micro-pulling-down method
We have grown the shape-controlled Sr<inf>3</inf>NbGa<inf>3</inf>Si<inf>2</inf>O<inf>14</inf> (SNGS) and Sr<inf>3</inf>TaGa<inf>3</inf>Si<inf>2</inf>O<inf>14</inf> (STGS) langasite-type crystals by the μ-PD method. Columnar-shaped SNGS and STGS crystals were grown using the Pt-Rh crucible with a columnar die in 3 mm diameter. Grown crystals indicated high transparency and approximately 3 mm diameter. Chemical phases of grown crystals were identified as a single phase of langasite-type structure. The lattice parameters of grown crystals were almost consistent with those of crystals grown by Czochralski (Cz) method. In the X-ray rocking curve measurements, the grown crystals indicated equivalent crystallinity to the crystal grown by Cz method.
Growth and physical properties of Al doped Ca 3 NbGa 3 Si 2 O 14 piezoelectric single crystals
Ca 3 Nb(Ga 1−x Al x ) 3 Si 2 O 14 (CNGAS) crystals with various Al concentrations were grown by a micro-pulling-down (μ-PD) method and their crystal structures, chemical compositions, crystallinities were investigated. CNGAS crystals with x = 0.2, 0.4 and 0.6 indicated a single phase of langasite-type structure and the crystals with x = 0.8 and 1 included some secondary phases in addition to the langasite-type phase by the powder X-ray diffraction measurements. Lattice parameters, a and c-axes lengths, of the langasite-type phase systematically decreased with an increase of Al concentration.
Growth and Electric Properties of Al-Substituted Langasite-Type La3Ta0.5Ga5.5O14 Crystals at High Temperature
We report an effective substitution of aluminum for gallium in langasite-type La3Ta0.5Ga5.5O14 (LTG) crystals for use in a pressure sensor at high temperature. Al-substituted LTG (La3Ta0.5Ga5.5-xAlxO14; LTGAx) single crystals up to the solubility limit of x=0.5 have been grown by the conventional Czochralski technique. The electric properties of the LTGAx crystals were investigated and compared with those of LTG. By Al substitution, the piezoelectric constant d11 and the electromechanical coupling factors (k12) became slightly larger. The LTGAx crystals showed a lower temperature dependence of d11 and a higher electric resistivity ρ than those of the LTG crystals.