First electrochemical growth of Tb16O30 single crystal

Abstract

Single crystals of Tb16O30 (TbO1.875) were successfully grown for the first time by DC electrolysis of the Tb3+ ion conducting Tb2(MoO4)3 solid electrolyte at 11V, 900°C. The Tb16O30 phase is the intermediate phase of fluorite-related rare earth oxides and it is extremely difficult to grow in a single crystal form, because this intermediate phase is usually obtained as one of the mixture of the fluorite related TbOx phases. Because there are many non-stoichiometric phases in the terbium oxide system, it is impossible to grow a specific intermediate phase in a single crystal form by the conventional methods via melt. Although single crystals of TbOx have been recently obtained by anodic electrocrystallization from alkaline hydroxide melts containing TbCl3, the composition has been confirmed to be TbOx with 1.75<x<1.82. On the contrary, the presently developed DC electrolysis method can be simply applicable at moderate temperatures around 900°C to artificially grow an intermediate phase of Tb16O30 (x=1.875) in a single crystal form, which was evidenced by the electron diffraction patterns for each particle.