**7. Conclusion**

showed the films matched the Pr6O11 fluorite structure and the crystallite size was calculat‐ ed as 20 to 40 nm. Scanning electron microscopy was utilized to study the surface texture and microstructure of deposits. As-deposited films had uniform morphology but sinter‐ ing caused cracking of the films. SEM showed interesting surface texture and platelet structure for the deposits. The oxidation state of Pr oxide was determined by XPS and revealed that the praseodymium oxide was non-stoichiometric with the oxidation state of

The remaining literature for electrodeposition of pure rare earth oxides is sparse. Most of the research is on doping of CeO2 with another rare earth oxide (i.e., PrO2, Sm2O3, Gd2O3, and Tb2O3) to increase the oxygen vacancies, ionic conductivity, or catalytic activity [106-109]. However, there are a few reports of individual REO coatings prepared by electrodeposition using the base generation method. Lair et al. prepared Sm2O3 by electrodepositing Sm(OH)3

films were thick and adherent to the substrate even though cracking was observed in the film. Raman spectra of the as-deposited films had peaks at 1054 and 741 cm-1 attributed to the internal vibration modes of nitrate ions. Both nitrate-related peaks greatly diminished after

Other researchers prepared Gd2O3 by electrodepositing Gd(OH)3 from a nitrate solution and

where ton = 10 ms and toff = 10 ms. The deposition mechanism was still a base generation method:


( ) 3+ - 2 2 <sup>3</sup> Gd + 3OH + yH O Gd OH yH O ® é ù

( )( ) ( ) 3+ - - 3 2 3 2 3-x <sup>x</sup> Gd + 3OH + xNO + yH O Gd OH NO yH O ® é ù

C for 3 h [111, 112]. The authors used a cathodic pulse current method



2 2 2H O +2e H + 2OH ® (17)

ë û (18)

ê ú ë û (19)

C for 1 h [110]. The as-deposited Sm-based

**6. Electrochemical synthesis of other rare earth oxides**

annealing and major peaks for Sm2O3 increased in the spectrum.

from a nitrate solution and then sintering at 600 o

Pr between +3 and +4.

100 Advanced Ceramic Processing

then sintering at 700 o

Electrochemical step:

Chemical step:

The electrodeposition of rare earth oxides onto various substrates can be accomplished by two different electrochemical mechanisms: cathodic electrogeneration of base method or direct anodic deposition. The majority of the literature for REO electrodeposition covers CeO2 or REO-doped CeO2. A variety of morphologies has been obtained for the REOs films, such as nanocrystalline films, nanorods, nanotubes, nanosheets, as well as flower-like and coral-like nanostructures. Some sections covered in detail include the direct electrodeposition of CeO2 using a complexing ligand to stabilize the ceria ions in solution and the cathodic deposition of Pr6O11.
