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 dielectric properties of Ca3NbGa3Si2O14 crystals
Abstract A new langasite type single crystal Ca 3 NbGa 3 Si 2 O 14 (CNGS) was grown by Czochralski (CZ) method. The structure of CNGS crystal was determined by X-ray powder diffraction, the lattice parameters were a =0.8087 ± 0.0001 nm, c =0.4974 ± 0.0002 nm, V =0.2817 ± 0.0002 nm 3 ; The congruency of CNGS was examined by measuring the chemical composition of the grown crystal by quantitative X-ray fluorescent (XRF) analysis. The melting point of CNGS crystal was measured by using the differential scanning calorimetry (DSC). Dielectric properties of (1 1 0) wafer plate were studied in the temperature range from 298.15 to 873.15 K; the frequency dependence of dielectric loss in the frequency range 10 Hz–13 MHz was measured.
Dramatic effects of excess oxygen on physical properties and crystal structure of La0.95Sr0.05MnOy single crystal
Abstract We have examined the effects of excess oxygen on the magnetization, electrical transport properties and crystal structure of La 0.95 Sr 0.05 MnO y . An antiferromagnetic insulator phase confirmed in the as-grown crystal at low temperatures changed to a ferromagnetic insulator phase after the introduction of excess oxygen. The ferromagnetic transition temperature, T C , systematically increased with increasing oxygen content, y , due to an increase in the mean valence of manganese. However, the T C of crystals with excess oxygen was lower than that of the La 1− x Sr x MnO 3.00 having identical manganese valence. This is considered to be a result of the competition among the mean valence of manganese, the concentration of cation vacancies, and the mean ionic radius of cations at the A-site.