Growth of lead barium niobate (Pb_1-xBa_xNb₂O₆) crystals by the vertical Bridgman method II. Sr_0.61Ba_0.39Nb₂O₆-seeded growth

Pb_1-xBa_xNb₂O₆ (PBN) single crystals have been grown by the vertical Bridgman method in the composition range of 1 - x = 0.5-0.6. Centimeter size crystals have been grown using Sr_0.61Ba_0.39Nb₂O₆ (SBN 61) single-crystal seeds which have the same tungsten bronze structure and a higher melting temperature. Compositional analysis of the PBN boules revealed that mass transport in the melt is dominated by diffusion, making possible crystals of uniform axial composition from an incongruent melt composition. A crystal grown at 1 mm/h exhibited a radial composition inhomogeneity caused by a concave melt/solid interface. When the growth rate was reduced to 0.5 mm/h, the interface became almost planar and thus little compositional inhomogeneity in the radial direction was found. A Ce-doped PBN crystal has also been grown using a PBN single-crystal seed. The Ce-doped crystal had an orange to brown color, in contrast to the light yellowish color of undoped crystals, and had a broadband absorption, from near the interband transition throughout most of the visible spectrum.