Title :
ITC technique as a tool to monitor a new phase nucleation in LiF-Ti single crystals
Author :
Capelletti, Rosanna ; Mora, Carlo ; Prato, Stefano ; Földvári, Lstvan
Author_Institution :
Dept. of Phys., Parma Univ., Italy
fDate :
8/1/1992 12:00:00 AM
Abstract :
Thermal treatment of LiF:Ti3+ at temperatures close to the melting point in moist atmosphere causes the growth of new phase occlusions. Optical and electron microscopy and X-ray diffraction have shown that they are parallelepipeds and cubes of a FCC phase coherent with the host matrix. ITC spectra (in the range 100 to 380 K) support that the crystal behaves as a heterogeneous dielectric: in fact the occlusion growth is accompanied by the appearance of new ITC bands at the expense of the band due to the reorientation of dipoles built by Ti 3+ and two cation vacancies. OH ions play a key role in such a process as supported by isotopic substitution experiments with OD and by infrared absorption spectra. The nucleation kinetics have been studied in such a way, and the Maxwell-Wagner-Sillars model has been applied, to interpret the new ITC bands
Keywords :
crystal microstructure; electron microscope examination of materials; heat treatment; impurity and defect absorption spectra of inorganic solids; inclusions; infrared spectra of inorganic solids; lithium compounds; nucleation; optical microscopy; solid-state phase transformations; thermally stimulated currents; titanium; 100 to 380 K; FCC phase; ITC bands; ITC spectra; LiF:Ti single crystals; Maxwell-Wagner-Sillars model; OH ions; X-ray diffraction; cubes; electron microscopy; heterogeneous dielectric; infrared absorption spectra; isotopic substitution experiments; moist atmosphere; nucleation kinetics; occlusion growth; optical microscopy; parallelepipeds; phase nucleation; phase occlusions growth; Atmosphere; Dielectrics; Electron microscopy; Electron optics; FCC; Monitoring; Optical diffraction; Optical microscopy; Temperature; X-ray diffraction;
Journal_Title :
Electrical Insulation, IEEE Transactions on
