The growth and optical properties of Bi12SiO20 single crystals

Single crystals of Bi12SiO20 were grown from the melt by the Czochralski technique. The critical crystal diameter dc=10 mm and the critical rate of rotation ?c=20 rpm were calculated by equations from the hydrodynamics of a melt. The rate of crystal growth was experimentally obtained to be 5 mm/h. The crystal growth was in the [111] direction. The lattice parameter a=1.0096nm was determined by X-ray powder diffraction. The reflectance spectra were recorded in the wave numbers range 20?5000 cm-1 at different temperatures. For all the recorded spectra the values of the vibrational TO and LO modes were found using the Kramers-Kronig analysis (KKA). Twentyfive TO and LO modes were found at 70 K, and eighteen at 295 K. The obtained results are discussed and compared with published data. Monokristali Bi12SiO20 su rasli iz rastopa po metodi Cohralskog. Vrednosti kritickog precnika kristala dc=10 mm i kriticne brzine rotacije ?c=20 o/min su izracunate koriscenjem jednacina dinamike fluida. Brzina rasta kristala od 5 mm/h je odredjena eksperimentalno. Kristal je rastao u pravcu [111]. Pomocu rendgenske difrakcione analize sprasenog uzorka odredjen je parameter resetke a=1,0096 nm. Refleksioni spktri su snimljeni na razlicitim temperaturama u ospegu talasnih brojeva 20?5000 cm-1. Pomocu Kramers-Kronig analize odredjene su vrednosti TO i LO modova za sve spektre. Nadjeno je 25 TO i LO modova na 70 K i 18 TO i LO modova na 295 K. Dobijeni rezultati su diskutovani i poredjeni sa literaturnim podacima.