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The langasite-type Ca3NbGa3Si2O14[CNGS] piezoelectric crystals grown in Air and Ar were annealed under various temperatures and atmospheres and the effects of annealing on various properties were investigated. The absorption peaks around 360 and 500 nm of CNGS crystals grown in Air decreased by the annealing at 1300°C in Ar. On the other hand, the annealing at 1300°C in Air decreased transmittance in the range from 300 to 500 nm for the CNGS crystal grown in Ar. The results suggest that the absorptions around 350 and 500 nm originate from the excess oxygen and the post-annealing can control the oxygen content in the crystals. [ABSTRACT FROM AUTHOR]

Ca3NbGa3Si2O14(CNGS) single crystals were grown by the micro-pulling-down (μ-PD) method under various atmosphere, Air, Ar + 3%O2and Ar 100%, and the effects of growth atmosphere on crystal growth and optical properties were investigated. While the CNGS crystal grown in Air indicated orange color, the crystal grown in Ar was colorless. CNGS crystal grown in Air indicated several large absorption peaks around 360 and 500 nm in the transmittance spectrum. In contrast, the crystal grown in Ar didn't indicate these absorption peaks. [ABSTRACT FROM AUTHOR]

We have grown shape-controlled langasite-type crystals by the micro-pulling-down (μ-PD) method. Columnar shaped La3Ta0.5Ga5.5O14 (LTG), Ca3NbGa3Si2O14 (CNGS), Ca3TaGa3Si2O14 (CTGS), Sr3NbGa3Si2O14 (SNGS), and Sr3Ta- Ga3Si2O14 (STGS) crystals were grown using a Pt-Rh crucible with a 3-mm-diameter columnar die at the bottom. All grown crystals showed high transparency except for the peripheral area and diameter of approximately 3 mm. The chemical phases at the central parts of the grown crystals were identified as a single phase of langasite-type structure and their lattice parameters were almost the same as those of crystals grown by the Czochralski (Cz) method; however, some impurity phases were observed in the peripheral area. In X-ray rocking curve measurements, the grown crystals indicated equivalent crystallinity to the crystal grown by the Cz method. The piezoelectric constant d11 of the CNGS crystal was 3.98 pC/N; this value is well correlated with those of previous reports. [ABSTRACT FROM AUTHOR]

We grew column-shaped Sr3NbGa3Si2O14 (SNGS) and Sr3TaGa3Si2O14 (STGS) langasite-type piezoelectric single crystals by the micro-pulling-down (μ-PD) method. 3-mm-diameter SNGS and STGS crystals were grown using a Pt-Rh crucible with a 3-mm-diameter columnar die. According to X-ray rocking curve measurements, the grown crystals had crystallinity equivalent to that of crystals grown by the Czochralski (Cz) method. The crystals were single-phase materials with langasite-type crystal structure. The lattice parameters of the grown crystals were almost consistent with those of crystals grown by the Cz method. [ABSTRACT FROM AUTHOR]

Abstract: Columnar-shaped La3Ta0.5Ga5.5O14 single crystals with a-axis and c-axis crystal orientations along the growth direction grown by the micro-pulling-down method and their physical properties were investigated. All diffraction peaks of the XRD pattern were identified as the langasite-type structure and the a-axis and c-axis lengths were a=8.239Å and c=5.124Å, respectively. In the XRC measurement, a relatively sharp single peak was observed in the ω scan and the full width of half maximum was 82.1arcsec. According to the chemical analysis by the EPMA system, the main phase was composed of LTG with the cation ratio of La:Ta:Ga=3.31:0.465:5.22 and the LTG crystal included secondary phase, La–Ta–O system, in the periphery area. The piezoelectric constant d 11 that was measured using the plate-shape LTG crystal was 6.7pC/N. [Copyright &y& Elsevier]

Abstract: The Ca3NbGa3Si2O14 (CNGS) crystal was grown by the micro-pulling down (μPD) method and the annealing effect on physical properties of CNGS crystal was investigated in this study. And the effects of oxygen content on the physical properties were systematically studied. Additionally, Photoluminescence (PL)-Mapping and radioluminescence spectra of CNGS were observed. The absorption peaks were observed around 350 and 500nm. This absorption at 500nm was very sensitive to a quantity of excess oxygen in the CNGS crystal. In contrast, it is expected that the absorption of 350nm is related to a cation or anion defect. PL-Mapping indicated the emission around 400nm by excitation at 270 and 350nm wavelengths. The emission at 400nm is considered to originate from trapped electron at an anion or cation defect. The emission of the Alpha-ray excited spectra was very similar in comparison with PL-Mapping. [Copyright &y& Elsevier]