Hydrothermal Crystal Growth of BaPb_1–x Bi _x O₃ (0 ≤ x ≤ 0.30)

Abstract

BaPb_1–x Bi _x O₃ (0 ≤ x ≤ 0.30) single crystals with a very sharp transition to the superconducting state were grown hydrothermally at temperatures below 450°C. The optimum conditions to grow bulk single crystals of BaPb_1–x Bi _x O₃ in KCl solution were as follows: 4.5m KCl solution as a solvent; temperatures at the dissolution zone in a gold capsule, 400–450°C; temperature difference ΔT, 20–30°C; pressure, 1000 kg/cm². The composition of the grown crystals deviated slightly on the lean side of the Bi content from that of the original nutrient oxide particles. It was found that exact control of the composition of the grown crystals could be achieved by using calcined BaPb_1–x Bi _x O₃ with an adjusted composition x of perovskite structure starting material. The superconducting transition temperature, T _c, changed with the composition x. Single crystals with x = 0.24 showed a T _c of 11.7 K, and a transition temperature width of 1.8 K, which is the narrowest value reported so far.