Facetting and optical perfection in Czochralski grown garnets and ruby

Large, high optical quality single crystals of ruby have been grown successfully by the floating zone method under air atmosphere. The size of the grown crystal is typically 60-70 mm in length and 7-8 mm in diameter. The obtained crystals were red and did not have any macroscopic defects such as cracks and inclusions. Grown crystals were characterized by powder X-ray diffraction (XRD) methods, polarized optical microscopy, scanning electron microscopy (SEM). The absorption and fluorescence spectra were measured at room temperature and the dielectric constant measurements of ruby crystals were also presented. Defects occurring in single crystals of ruby during crystal growth by floating zone method are described, and their correlation with the growth parameters is discussed. The origin and control of these defects in grown crystals were studied and the optimum method was proposed.

Section: Resultsmentioning

confidence: 98%

Floating zone growth and characterization of ruby single crystals

Fan

Wang

et al. 2011

“…In one of the oldest reports reporting about the Czochralski growth of such crystals [1] the convex interface was noted to be dependent on crystal transmission and it was attributed to the transparent crystal as "… acting as a light (heat) guide …". Radiant heat transport is proportional to T 4 , with T the absolute temperature in Kelvin, as far as the material is fully transparent.…”

Section: Introductionmentioning

confidence: 98%

Transmission spectra of crystals at elevated temperatures for the calculation of internal radiant heat transport during crystal growth – Part 1: The spectrometer and its performance

Schwabe

Polity

2003

“…The melt-crystal interface shape and its changes during a growth process is one of the major factors determining the crystal quality. Many previous experimental studies showed that the interface shape of oxide crystals having a high melting point is related to heat transport via radiation within the crystal [1][2][3]. Because oxide crystals are semi-transparent to infrared radiation radiative heat fluxes through the crystal can be significantly larger than the conductive ones and thus should be included in theoretical simulations of the total heat transfer in the furnace.…”

Section: Introductionmentioning

confidence: 98%

Influence of internal radiation on the heat transfer during growth of YAG single crystals by the Czochralski method

Galazka

Schwabe

Wilke

2003

Heat and mass transfer taking place during growth of Y 3 Al 5 O 12 (YAG) crystals by the Czochralski method, including inner radiation, is analyzed numerically using a Finite Element Method. For inner radiative heat transfer through the crystal the band approximation model and real transmission characteristics, measured from obtained crystals, are used. The results reveal significant differences in temperature and melt flow for YAG crystals doped with different dopands influencing the optical properties of the crystals. When radiative heat transport through the crystal is taken into account the melt-crystal interface shape is different from that when the radiative transport is not included. Its deflection remains constant over a wide range of crystal rotation rates until it finally rapidly changes in a narrow range of rotation rates.