Synthesis of lanthanum oxyhydroxide single crystals using an electrochemical method

Single crystals of lanthanum oxyhydroxide (LaOOH) were grown using an electrochemical method. Crystals having a maximum size of 7.0 mm in length, 1.5 mm in width, and 0.7 mm in thickness were grown. LaOOH crystallizes in a monoclinic structure of the space group P 2 1 / m with a lattice parameter of a =0.4417 nm, b =0.3926 nm, c =0.6573 nm, and β =112.32°. LaOOH crystals completely changed to lanthanum trihydroxide La(OH) 3 within 48 h in ambient atmosphere by water absorption. Maintenance at 390 °C by heat treatment was effective to maintain the structure of LaOOH for at least a week.