Visualization of hydrogen isotope distribution in yttrium and cobalt doped barium zirconates

Tritium (T) distributions in yttrium (Y) and cobalt (Co) doped barium-zirconates (BaZrO₃) were visualized by imaging plate (IP) technique using HT gas (T/H = 10⁻⁴, ∼1.3 kPa) under various exposure temperatures (623 to 1273 K) and exposure times (5 min to 16 h). Two types of specimens, BaZr_0.9Y_0.1O_3-α (BZY) and BaZr_0.955Y_0.03Co_0.015O_3-α (BZYC), were prepared with conventional powder metallurgy: disk-shaped specimens were obtained with more than 97% of the theoretical densities. With IP method, uniform tritium distribution was found on the surface of both T-exposed specimens. The T distributions of the cross sections of the cut-in-half specimens were also examined with IP, which showed that more T was diffused into BZYC compared to BZY. The diffusivities of T and hydrogen solubility were determined by the T concentration profiles for the BZY and BZYC samples at different exposure conditions. Almost one order higher solubility and diffusivity for BZYC than BZY was found. It suggests that only a small amount sintering-aid cobalt doping along with yttrium may play a vital role of enhancement of electrochemical activity of the proton conducting BaZrO₃ under HT exposure condition.