Japan is facing a challenge of wide-spread radioactive contamination by isotopes of cesium (Cs). Here we demonstrate that titanium oxide (TiO
2) can be an efficient material to immobilize high concentrations of Cs ions in a durable solid-state framework. TiO
2 was dissolved in a Cs-containing melt of molybdenum trioxide (MoO
3) at 950
oC. The melt was then electrolyzed at −1200mV (vs. a Pt reference electrode) to obtain a single-crystalline titanate, Cs
0.169TiO
2 (titanium-oxide immobilizer) , which contained 1g cm
−3 of Cs. Moreover, the titanium-oxide immobilizer exhibited a 170 times lower Cs leaching rate than did Cs-containing borosilicate glass. The titanium-oxide immobilizer will contribute to the Cs decontamination because of its high Cs content and low Cs leaching.
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