| In this paper, many experiments were carried out to grow the La3Ga5SiO14 (LGS) single crystal and its isostructural compounds A3BGa3Si2O14(A=Ca, Sr; B=Nb, Ta)series of single crystals by using the czochralski technology. The optimal growth procedure was investigated and crystals with high quality were gained. Their properties were widely studied, especially the calorific parameters and their effects on the crystals growth. The main works of the article are as follows:1. Slope shoulder and flat shoulder crystal growth of LGS were studied. The optimal growth procedure for getting crystals with high quality was investigated. X-ray power diffraction analysis confirmed that all grown LGS crystals were single phase and of Ca3Ga2Ge4O14-type structure. All the diffraction peaks were identified to be those for LGS and no peaks of a second phase were found. The optical transmission spectra of LGS crystal were measured by using a Hitachi model UV/Vis/NIR Hitachi U-3500 at room temperature in the range of 190-3200 nm with a slit width of 3.0mm. The scan speed was 120nm/min and the sampling interval was 1nm, the light path direction were normal to the test plane, and found the crystal had high transmission, the highest transmittance is 83%; Furthermore, it showed that the transmittance would be much higher if the growth atmosphere contained less oxygen.The melt points of crystal were measured by Netzsch differential scanning calorimetric(DSC) SAT409 EP, and found that the melt point of crystal grown with high purity raw materials was about 1480℃, however, which was 1371℃when the crystal grown with analyse purity raw materials, the difference might due to low purity of raw materials(99%La2O3, 98Ga2O3, 99%SiO2). The specific heat of LGS crystal were 0.6J/g.Kand 0.90J/g.K at 298.15Kand 453.15K, respectively. The data of thermal expansion coefficient along Y and Z direction have been measured to be 5×10-6K-1 and 3.8×10-6K-1, respectively.2. A3BGa3Si2O14 (ABGS, A=Ca2+, Sr2+; B=Nb5+, Ta5+) series of crystals were grown based on the growth of LGS crystal. The structure of Ca3TaGa3Si2O14 (CTGS) single crystal was determined by BRUKER-P4 four-circle diffractometer, which showed that it was isostructrural to LGS crystal and belonged to 32 point group. The structure was confirmed by X-ray powder diffraction method, the cell parameters were calculated to be: CNGS : a=8.0869(?), c=4.9743(?); CTGS: a=8.0983(?), c=4.9769(?); SNGS: a=8.1621(?), c=5.0808(?); STGS: a=8.3327(?), c=5.0945(?), respectively. The transmittance spectum were measured in the range of 200-3200 nm, and the optical beam was normal to (010) plane, and found that all the cutoff wavelengths were 250nm-300nm, the highest transmittance were above 82%.The results of DTA showed that the melt point of four crystals at room temperature were CNGS: 1349.9℃, CTGS: 1368℃, SNGS: 1415.4℃, STGS: 1364.8℃, respectively. The specfic heat of CNGS,CTGS,SNGS and STGS crystal at room temperature were 554.9671, 411.0496, 447.9083, 457.2141 J/mol.K, respectively. The thermal expansion coefficients of four crystals were increased linear with the increase of the temperature between 283.15K and 403.15K, and the thermal expansion coefficients are CNGS:α1=1.7×10-6/K,α3=0; CTGS:α1=3.7×10-6/K,α3=5.2×10-6/K; SNGS:α1=7.0×10-6/K,α3=2.7×10-6/K; STGS:α1=9.7×10-6/K,α3=3.2×10-6/K, respectively. |
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