TY - JOUR
T1 - Surface growth mechanisms and structural faulting in the growth of large single and spherulitic titanosilicate ETS-4 crystals
AU - Miraglia, Peter Q.
AU - Yilmaz, Bilge
AU - Warzywoda, Juliusz
AU - Sacco, Albert
N1 - Funding Information:
The authors acknowledge the financial support of NASA, and Dr. Steven M. Kuznicki for an introduction to the ETS materials.
PY - 2004/10/1
Y1 - 2004/10/1
N2 - Morphological, surface and crystallographic analyses of titanosilicate ETS-4 products, with diverse habits ranging from spherulitic particles composed of submicron crystallites to large single crystals, are presented. Pole figures revealed that crystal surfaces with a-, b- and c- axes corresponded to 〈110〉, 〈010〉 and 〈001〉 directions, respectively. Thus, technologically important 8-membered ring pores and titania chains in ETS-4 run along the b-axis of single crystals and terminate at the smallest crystal face. Height of the spiral growth steps observed on {100} and {001} surfaces corresponded to the interplanar spacings associated with their crystallographic orientation, and is equivalent to the thickness of building units that form the ETS-4 framework. Data suggest that the more viscous synthesis mixtures, with a large driving force for growth, increased the two- and three-dimensional nucleation, while limiting the transport of nutrients to the growth surface. These conditions increase the tendency for stacking fault formation on {100} surfaces and small angle branching, which eventually results in spherulitic growth. The growth of high quality ETS-4 single crystals (from less viscous synthesis mixtures) occurred at lower surface nucleation rates. Data suggest that these high quality, large crystals grew due to one-dimensional nucleation at spiral hillocks, and indicate that under these conditions un-faulted growth is preferred.
AB - Morphological, surface and crystallographic analyses of titanosilicate ETS-4 products, with diverse habits ranging from spherulitic particles composed of submicron crystallites to large single crystals, are presented. Pole figures revealed that crystal surfaces with a-, b- and c- axes corresponded to 〈110〉, 〈010〉 and 〈001〉 directions, respectively. Thus, technologically important 8-membered ring pores and titania chains in ETS-4 run along the b-axis of single crystals and terminate at the smallest crystal face. Height of the spiral growth steps observed on {100} and {001} surfaces corresponded to the interplanar spacings associated with their crystallographic orientation, and is equivalent to the thickness of building units that form the ETS-4 framework. Data suggest that the more viscous synthesis mixtures, with a large driving force for growth, increased the two- and three-dimensional nucleation, while limiting the transport of nutrients to the growth surface. These conditions increase the tendency for stacking fault formation on {100} surfaces and small angle branching, which eventually results in spherulitic growth. The growth of high quality ETS-4 single crystals (from less viscous synthesis mixtures) occurred at lower surface nucleation rates. Data suggest that these high quality, large crystals grew due to one-dimensional nucleation at spiral hillocks, and indicate that under these conditions un-faulted growth is preferred.
KW - A1. GADDS, A1. Growth models, A1. Surface structure
KW - A2. Single crystal growth
KW - B1. ETS-4
KW - B1. Titanosilicates
UR - http://www.scopus.com/inward/record.url?scp=4544253669&partnerID=8YFLogxK
U2 - 10.1016/j.jcrysgro.2004.06.032
DO - 10.1016/j.jcrysgro.2004.06.032
M3 - Article
AN - SCOPUS:4544253669
SN - 0022-0248
VL - 270
SP - 674
EP - 684
JO - Journal of Crystal Growth
JF - Journal of Crystal Growth
IS - 3-4
ER -