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Optical Floating Zone Growth And Characterization Of Mullite Crystal And Cr:Mullite Crystal

Posted on:2016-09-14Degree:MasterType:Thesis
Country:ChinaCandidate:C P ZhangFull Text:PDF
GTID:2271330503950703Subject:Optical Engineering
Abstract/Summary:PDF Full Text Request
Mullite crystals and Cr-doped mullite crystals were grown out by the optical floating zone method crystal growth technique. And the as-grown crystals samples were characterized by X-ray diffraction, single crystal X-ray diffraction, electron scanning electron microscope, Raman spectra, dielectric, transmittance, photoluminescence spectra. It was researched systematically the crystal phase, growth orientation, microstructure, dielectric properties and optical properties of the mullite crystals and Cr-doped mullite crystals.Firstly, the factors such as the preparation polycrystalline rods, rotation rate, growth rate and seed crystal quality on the crystal quality were analyzed. The growth parameters were optimized and the optimal growth conditions as follows: the sintering temperature of raw materials is 1550 ~ 1550 ℃, the power of heating lamps is ranging from 18% to 25%, rotation speed is 20 ~ 30 rmp, growth speed is 2 ~ 10 mm/h and mullite crystals were grown in air. The mullite single crystal with 6 ~ 8 mm in diameter and 30 ~ 60 mm in length were successfully grown. XRD results showed that the mullite single crystal was orthorhombic and grown along the c axis orientation. The mullite crystals after one-step melting were eutectic structure and high quality mullite single crystal can be obtained after three-step melting. Physical property test results showed as follows: The mullite crystals in the visible and near infrared band have high transmittance and low cutoff frequency. It is the high quality high temperature transparent window materials; The dielectric tensor of constant and dielectric loss of mullite crystals [100], [010], [001] direction both were low at 1 MHz under room temperature. The high temperature dielectric properties of the mullite crystal(100) and(001) section in four frequency(1 kHZ, 10 kHZ, 100 kHZ, 1 MHZ) were measured, with the temperature range from the room temperature to 280 ℃. The dielectric constant and dielectric loss under high temperature of the mullite crystals has smaller changes and the dielectric properties were stable. It can be used for electronic packaging materials; Mullite crystals has main fluorescent emission peak at 774 nm and the peak intensity is stronger. It indicated that mullite crystals had application prospect in the laser medium.Secondly, Cr-doped mullite crystals with doping concentration 0.05 mol%, 0.10 mol% and 0.15 mol% were grown out by optical floating method. Cr-doped mullite crystals were suitable for growth under argon atmosphere environment to prevent oxidation and volatilization. X-ray diffraction, single crystal X-ray diffraction, electron scanning electron microscope(SEM), photoluminescence spectra of Cr-doped mullite crystals samples were tested. It determined that Cr-doped mullite crystals were grown along [001] orientation. It was also eutectic structure. Meanwhile Cr-doped mullite crystals had good photoluminescence properties and it was considered to have application in the field of laser.
Keywords/Search Tags:3/2 Mullite crystal, Cr-doped mullite crystal, Optical floating zone method, dielectric properties, optical properties
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