Structural modifications in titania-doped tantalum pentoxide crystals: a Raman scattering study

Tantalum pentoxide (Ta2O5) is promising for coating and piezoelectric applications and has been considered as the dielectric gate material for the next generation of memory devices. In this work, TiO2-doped Ta2O5 crystals were prepared using the laser-heated pedestal growth technique, as grown specimens were found to crystallize in monoclinic phase at room temperature. The structural modifications in these crystals resulting from variation of TiO2 composition (0-11%) and temperature (-248-900 degreesC) were studied using Raman spectroscopy. The low frequency external modes (upsilon < 100 cm(-1)) that originate from the interaction between TaOn5-2 eta/Ta6O12+6 clusters/polyhedra exhibit a strong compositional and temperature dependence in terms of their intensity and frequency variations. The Raman spectral evolutions suggested a monoclinic to orthorhombic structural phase transition at about 327, 397, 487, and 577 degreesC For 0, 5, 8, and 11% TiO2-doped Ta2O5, respectively. (C) 2001 Elsevier Science Ltd. All lights reserved.