Voids engulfment in shaped sapphire crystals

Study of the gas inclusions in Al2O3/Y3Al5O12 and Al2O3/Y3Al5O12/ZrO2 eutectic fibers grown by laser floating zone

“…3(a) shows that the bubble diameter in AY eutectic crystals decreases when the growth rate raises. The decrease in the bubble size with the growth rate has been previously reported in the solidification of gas-saturated water [29,30] and in sapphire single crystals grown by floating zone method [22,23,31] The dependence of the pore diameter with the growth rate is in agreement with the mechanism explained above. Once nucleated the bubble in the melt, the gas inclusion will ARTICLE IN PRESS grow when the solid front approaches as the gas concentration around the bubble increase.…”

Nd:YVO4 crystal growth by Czochralski technique with a submerged plate

“…By increasing crystal rotation rate, the precipitated composition spreads over the growing interface. Further increasing crystal rotation rate, the solidification interface will change initially from flat to concave shape [9,15]. The precipitated composition can be taken away from the interface by increasing the forced convection through crystal rotation.…”

“…For example, melt inclusions in the Cz-grown CaWO 4 crystals were considered to be related to constitutional supercooling combined with the segregation of impurities and basic constituents, and the predominating factor was the entrapment of impurity-rich liquid or solute trail [8]; void distribution and its engulfment in the shaped sapphire crystals were a strong function of pulling rate and shaper design [9], and air-bubble formation was extensively studied, and the bubble generation and entrapment mechanism was proposed [10]. As to the Nd:YVO 4 crystals, melt inclusions in the crystal are mainly constituted by micro-pieces of the segregation phases of the binary compound system Y 2 O 3 and V 2 O 5 , or V 2 O 3 and YVO 3 formed during growth [4][5][6].…”

Haze in sapphire crystals grown by SAPMAC method

“…Haze composed by gaseous inclusions (bubbles) has been frequently observed in sapphire crystals grown by many methods such as Edge-defined Film-feed Growth (EFG) [5][6][7][8][9][10][11][12][13]. It is believed that the gaseous composition depends on the growth atmosphere.…”

“…Mass spectrometry indicated that the gases in the pores maybe H and CO, also Peaks of lower intensities with mass numbers 12 (carbon), 14 (N, CH 2 ), 16 (O, CH 4 ), 32 (O 2 ), 44 (CO 2 ), and 68 (C 3 O 2 ) sometimes were seen [5,14]. The researches of EFG method showed the bubbles are incorporated in the position close to die, that means in the periphery of the crystal grown with a central capillary channel die and in the periphery and the core of the crystal grown with a annular capillary channel die, and increasing the pulling rate will enlarge the volume of haze, so when the rate exceeds a critical value, the haze will distribute in whole crystal [12,13]. The spacing of the bubble arrays in the rod-shaped sapphire crystals grown using a central capillary channel die increases as the pulling rate increases with a linear dependence [9].…”