近化学计量比铌酸锂晶体中机械孪晶的消除

在用掺钾的助熔剂提拉法生长近化学计量比LiNbO3晶体时,长出的晶体尾部很容易出现孪晶裂纹现象,这种孪晶被认为是机械孪晶.这种孪晶的起因是由于晶体生长的收尾和从熔体中提起晶体阶段,在晶体底部产生直径的缩进,在缩进产生的台阶处出现应力集中,从而造成孪晶的成核.通过采用适当的收尾过程,以避免直径台阶的出现,可以很好地消除这种孪晶及其引起的裂纹.

Mechanical Twinning Elimination in Near Stoichiometric Lithium Niobate Crystal

Using Czochralski method, a near-stoichiometric LiNbO_3 crystal can be grown from K_2O-containing melts.Many twins identified as mechanical twins appear at the bottom of the as grown crystal. These mechanical twins are formed during the process of tailing as well as the process of polling the crystal out of the melt. Accompanied with these processes,high stresses appearing at the diameter shrinkage make mechanical twins nucleate. By a approprate tailing process, the diameter shrinking can be avoided, resulting in the elimination of mechanical twins.