Raman and Infrared Spectra of YAsO4

Single crystals and polycrystalline specimens of YAsO4 are prepared by flux method and solid‐state reaction, respectively. Crystal and powder Raman and infrared spectra at 300 K and crystal Raman spectrum at 77 K of YAsO4 are taken to study the internal and external vibrations of AsO4−3 ions. It is found that lattice vibrations with k = 0 associated with the tetrahedra of YAsO4 are similar to that of DyAsO4 and SmAsO4. The Raman spectrum at 77 K shows slight shifting of phonon lines to higher frequencies due to the decreasing anharmonic interactions of the vibrations. Similarly softening of one of the force constants (f4) at 77 K in comparison to that of 300 K was observed. Different dosages of X‐ray irradiation produces a very little effect to create defects in the YAsO4 crystals.