Raman and IR studies of TaWO5.5, ASbWO6 (A = K,Rb, Cs,Tl), and ASbWO6·H2O (A = H,NH4, Li,Na) pyrochlore oxides

Raman and infrared (IR) spectra of defect pyrochlores TaWO_5.5, NH₄SbWO₆·H₂O, HSbWO₆·H₂O, LiSbWO₆·H₂O, NaSbWO₆·H₂O, KSbWO₆, RbSbWO₆, CsSbWO₆, and TlSbWO₆ were measured. The obtained spectra are discussed using the factor group approach for the cubic Fd‐3m space group, and assignment of bands to respective motions of atoms is proposed. Our results show that the phonon properties of the pyrochlores are strongly affected by disorder, and therefore Raman and IR spectroscopies are very useful tools in studying disorder in this family of compounds. In particular, our studies have shown that in these ionic conductors disorder at sites occupied by NH , H⁺, or alkali‐metal ions decreases with increasing size and mass of these ions. Copyright © 2010 John Wiley & Sons, Ltd.