Crystal growth of BaTi2O5 by the floating zone method

•A large single-crystalline BaTi2O5 was synthesized by the FZ method.•The steep temperature gradient was introduced by masking of the molten zone.•The melt-solidification was pseudo-congruent by masking.•The BaTi2O5 was grown to the b-axis and had facets of the c-plane.•The optical transmittance of BaTi2O5 showed almost 100%.

Transparent single-crystalline BaTi2O5 was prepared by the floating zone (FZ) method. A large size single-crystalline BaTi2O5 rod, 5.5 mm in diameter and 30 mm in length, was prepared by masking the molten zone with Al foils in FZ. The growth direction was perpendicular to the (020) plane. The single-crystalline BaTi2O5 rod had (002) facets parallel to the growth direction. The optical transmittance of single-crystalline BaTi2O5 was almost 100% in the visible region after post-annealing in air for 3.6 ks.