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

Abstract Tantalum pentoxide (Ta 2 O 5 ) 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, TiO 2 -doped Ta 2 O 5 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 TiO 2 composition (0–11%) and temperature (−248–900°C) were studied using Raman spectroscopy. The low frequency external modes ( v −1 ) that originate from the interaction between TaO 5−2 n n /Ta 6 O +6 12 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°C for 0, 5, 8, and 11% TiO 2 -doped Ta 2 O 5 , respectively.