Characterization of low angle grain boundaries in yttrium orthovanadate

Single crystals of Nd:YVO4 grown with the Czochralski technique frequently exhibit light scattering defects that are detrimental to their lasing and optical properties. Defects in the form of low angle grain boundaries have been characterized in what are nominally ‘single crystals’. The misorientation angles of the boundaries were determined to be typically < 1°, which corresponds to formation energies of approximately 1 Jm−2. It was found that dislocations generated during crystal growth and cooling have enough mobility in certain growth directions to form low angle grain boundaries through polygonization. Despite the relatively high energies the boundaries were stable, being immobile at annealing temperatures up to 97% of the melting point (2083 K). Suggestions are made to reduce or eliminate polygonization, including the addition of atoms with a size either much larger or smaller than Y3+.