Quartz crucibles may encounter some problems during the process of pulling single crystals,such as crystallization,deformation,etc.There is also a situation where brown small circles appear on the pot wall,making it unstable at high temperatures.Below are the reasons and solutions for this phenomenon:
Analysis of the reasons for this phenomenon:
The quartz crucible itself is an amorphous intermediate state energy,and under appropriate conditions,it will undergo phase changes to form a stable quartz crystal state.The initial quartz crystals are spherical in shape,and further growth occurs in a branched manner along the crucible wall towards the lateral direction.This is because the vertical growth during the reaction between the vessel and the solution is suppressed.There is usually a layer of silicon solution sandwiched between the walls of the quartz crystal and amorphous crucible,and the edges of the quartz crystal are usually covered with brown SiO bubbles.The SiO gas is brown,and the brown small circles are SiO crystals.
The root cause is the impurities on the quartz crucible wall or the acid,alkali,or heavy metal residues caused by poor cleaning of the silicon material,resulting in the above phenomenon.
Solution:
(1)The cleaning of silicon materials needs to ensure that there are no acid or alkali residues or heavy metals;(2)The quality of the crucible itself is up to standard;(3)Improve the process by using coated or sprayed crucibles.
The reason for the appearance of brown circles in quartz crucible pulling single crystals was analyzed in the previous text.It was caused by poor cleaning,which affected the stability of the vessel.Therefore,in the future,the cleaning method summarized earlier can be used to ensure its cleanliness.In addition,the first thing to ensure when purchasing is the quality of the product,so as to avoid this situation from happening.