Infrared Spectral Emittance and Optical Properties of Yttrium Vanadate

The infrared spectral emittance E of single scrystals of YVO₄ has been examined near 4.2 and 77°K in the wavelength range 4-125 μm. Of the expected seven active transverse optical modes at k∼0, six have been observed and assigned to their symmetry species based on their polarization with respect to the crystalline axes. The observed frequencies of the transverse optic E_u modes were 196, 261, and 788 cm^-1; and for A_2u modes, 310, 455, and 803 cm^-1. The relation between emittance and reflectance, E=1-R in the opaque region of lattice vibrations, permits one to determine the reflectance R. By least-square-fitting the reflectance data to an independent set of damped harmonic oscillators, infrared dispersion parameters were determined for the E_u vibrations.