Accession Number : AD0710236

Title :   CRYSTAL GROWTH OF CaWO4 AND Nd2(CO3)3.8H2O BY THE GEL TECHNIQUE.

Descriptive Note : Technical rept.,

Corporate Author : ARMY MATERIALS AND MECHANICS RESEARCH CENTER WATERTOWN MASS

Personal Author(s) : McCauley,James W. ; Gehrhardt,Henry M.

Report Date : JUN 1970

Pagination or Media Count : 25

Abstract : Spherulites (up to 2 mm in diameter) and single crystals of CaWO4 have been synthesized by reacting CaCl2 and Na2WO4 within acetic acid-Na2SiO3.9H2O gels. High calcium concentrations favored the growth of clear spherulites, whereas high tungstate concentrations resulted in opaque spherulites. The addition of NH4Cl to the gel system lead to the formation of single crystal needles of CaWO4. Lavender-colored rhombic plates, dendrites, and spherulites of Nd2(CO3)3.8H2O were synthesized for the first time in a gel. Utilizing low pH HCl-Na2SiO3.9H2O gels, the crystals formed by recrystallization from an initial precipitate (perhaps Nd2(CO3)3.Na1CO3.nH2O) or at gel-gel and gel-bubble interfaces. Differential thermal analysis on the material showed that six waters of hydration are lost beginning at 77 C and the last two beginning at 121 C; infrared and visible absorption spectra were also obtained. In transmitted light microscopy all the crystals exhibited a highly symmetric domain structure and a resulting strain birefringence. (Author)

Descriptors :   (*CRYSTAL GROWTH, COLLOIDS), (*TUNGSTATES, CRYSTAL GROWTH), (*NEODYMIUM COMPOUNDS, CRYSTAL GROWTH), SINGLE CRYSTALS, CALCIUM COMPOUNDS, CARBONATES, SILICON DIOXIDE, IMPURITIES

Subject Categories : Crystallography

Distribution Statement : APPROVED FOR PUBLIC RELEASE