Homogeneity and composition of mixed flux-grown Dy (AsxV1- x) O4 crystals

Large flux-grown single crystals of Dy(As,,V, _,*)O, have been studied and characterized by X-ray powder diffraction, PIXE and EDX analyses, and optical birefringence. The crystal structure remains zircon throughout the composition range, and Vegard's law for the dependence of unit cell parameters on composition is obeyed well. The crystal As concentrations were much higher than those of the ingredient powders. The relative As/V incorporation in this lattice was found to be 3.23. Absolute indices of refraction were determined by observing white-light fringes in a Michelson interferometer. Birefringence measurements showed that As concentration gradients were small, typically less than lo-' mm-' in regions of good optical quality. Flux techniques are thus able to yield large mixed crystals of excellent uniformity.