Abstract
The temperature dependence of the reflectance of the cubic bismuth pyrochlores , , , and (BZN) has been investigated by infrared spectroscopy. Spectra were collected from between 50 and , and the optical constants were estimated by Kramers-Kronig analysis and classical dispersion theory. In addition, BZN was studied by terahertz techniques to lower frequencies. Infrared-active phonon modes have been assigned to specific bending and stretching vibrational modes. A previously unassigned infrared mode at is discussed. A splitting of the stretching phonon modes and bending modes is assigned to mixed-cation occupancy. The temperature dependence of the phonon frequencies and the damping coefficients are consistent with a decrease of both lattice constant and orientational disorder at low temperatures.
- Received 5 January 2005
DOI:https://doi.org/10.1103/PhysRevB.72.054303
©2005 American Physical Society