Segregation of impurities and striation in single crystals of double niobates BaxSr1−xNb2O6 and Ba2NaNb5O15

Crystal Growth from the Melt

“…While rotational striations (to be discussed in the next section) are characterized by a relatively simple structure and can be attributed to seed or crucible rotation, nonrotational striations are frequently complex and of varying origin. (130)(131)(132)(133)(134)(135)(136)(137)(138) The identification of the exact origin of the multiple of nonrotational striations has been complicated by our inability to establish unambiguous cause and effect relationships between phenomena in the melt and the corresponding growth and segregation behavior. From theoretical considerations it is clear that phenomena such as irregular crystal pulling, mechanical vibrations, and, particularly, fluctuations in melt temperature and flow will result in transient growth and segregation behavior.…”

A Mechanism for Generation of Pulsating Growth and Nonrotational Striations during Initial Transient of Solidification

“…; for R : 2.9 ~/sec: 10 sec, 35 sec, 73 sec, 124 sec, 179 sec, 245 sec, 1320 sec, etc. Fluid flow cycles that take minutes for each cycle to one correlation could not always be shown (e.g., 23,[32][33][34][35][36]. Additional underlying basic principles cannot be excluded.…”