Raman and Infrared Spectra of Nd-Doped Barium Sodium Niobate Crystals

Neodymium-modified barium sodium niobate (Ba₂Na)_1-xNd_xNb₅O₁₅(BNN:Nd), with x = 0.025, crystallizes with a filled tungsten bronze (TB) type structure in the tetragonal system, conforming to the space group P4bm and Z = 2. The lattice constants are a = 1.2446(1) and c = 0.3991(1) nm at room temperature. Tc = 537 +- 2 °C. The experiments show that the Nd-ions effectively improve crystal structural quality. The lattice vibrational spectrum, studied by Raman and infrared reflectivity spectroscopy, shows that the crystal microscopic structure and lattice dynamics, thereby the microstrain and microstress, are very stable in a temperature range from 22 to approaching 500 °C.