Physical and structural properties of Nd : YAG crystal growth by czocharalski method

Abstract

Neodymium doped Yttrium Aluminium Garnet, Nd:YAG crystal with nominal dopant concentration of 1.4 at. % was successfully grown by Czochralski technique equipped with an Automatic Diameter Control – Crystal Growth System (ADC-CGS). Correlation between dopant concentrations with the length of crystal boule in relation with physical and structural properties was studied. It was found that the crystal was partially transparent with some visible macroscopic defects such as cracks, gas pores, and inclusion. Its physical appearance is strongly affected by heat zone design. From EDX analysis, it was found that the doping concentration of Nd3+ ion increased as the crystal boule became longer than its initial pulling point. From the top to the bottom of Nd:YAG crystal boule, the concentration of Nd3+ changed from 0.13 at. % to 0.65 at. %. The density of the samples was determined by Archimedes method which showed an increasing trend of density with the crystal length which was found to be in the range of 4.5344±0.0153 gcm-3 to 4.5628±0.0114 gcm-3. It was also discovered that Vickers hardness increased with increasing dopant concentration which was from 1590 Hv to 1776 Hv. Raman spectrum was obtained in the range of 100 cm-1 – 1000 cm-1. From the spectra, the intensity was found to vary and shifting occured in the band due to the Nd3+ dopant concentration. Meanwhile, the IR spectra shows absorption occurring around 2000 cm-1 to 4500 cm-1. Absorption tends to be greater with increasing dopant concentration. Furthermore, the effect of melts level to the growth process has also been studied and it is suggested that the crucible should be lifted up according to the level of the melts drop during growing process to maintain the temperature gradient of the hot zone.