Vibrational Properties of LaNb 0.8 M 0.2 O 4-δ (M=As, Sb, V, and Ta).

LaNb 0.8 M 0.2 O 4-δ (where M=As, Sb, V, and Ta) oxides with pentavalent elements of different ionic sizes were synthesized by a solid-state reaction method. The vibrational properties of these oxides have been investigated. These studies revealed that the substituent element influences both Debye temperature value as well as the Raman active vibrational modes. Additionally, the low-temperature vibrational properties of LaNb 0.8 Sb 0.2 O 4-δ have been determined to show the phase transition occurrence at 260 K which is lower than previously reported.