In Situ High Pressure Structural Investigation of Sm-Doped Ceria

Abstract

As a result of the lattice mismatch between the oxide itself and the substrate, the high-pressure structural properties of trivalent rare earth (RE)-doped ceria systems help to mimic the compressive/tensile strain in oxide thin films. The high-pressure structural features of Sm-doped ceria were studied by X-ray diffraction experiments performed on Ce1−xSmxO2−x/2 (x = 0.2, 0.3, 0.4, 0.5, 0.6) up to 7 GPa, and the cell volumes were fitted by the third order Vinet equation of state (EoS) at the different pressures obtained from Rietveld refinements. A linear decrease of the ln B 0 vs. ln ( 2 V a t ) trend occurred as expected, but the regression line was much steeper than predicted for oxides, most probably due to the effect of oxygen vacancies arising from charge compensation, which limits the increase of the mean atomic volume ( V a t ) vs. the Sm content. The presence of RE2O3-based cubic microdomains within the sample stiffens the whole structure, making it less compressible with increases in applied pressure. Results are discussed in comparison with ones previously obtained from Lu-doped ceria.

High Pressure X-ray Diffraction as a Tool for Designing Doped Ceria Thin Films Electrolytes

“…The authors' research group focused on RE-doped ceria systems containing RE ≡ Lu [11], Sm [12] and a mixture of Nd/Tm ions [13]. In particular, the last-mentioned system was synthesized using a Nd/Tm = 0.74/0.26 ratio, in order to reproduce the average ionic size of Sm 3+ (C.N.…”

“…All the samples were prepared by coprecipitation of the corresponding mixed oxalates, and by subsequent thermal treatment at 1173 K for 3 days in order to obtain a high crystallinity degree, as thoroughly described in [41,76]. Going into detail, authors studied Ce 1−x RE x O 2−x/2 systems with x ranging between 0.1 and 0.4 for RE ≡ Lu [11], 0.2 and 0.6 for RE ≡ Sm [12], and 0.1 and 0.6 RE ≡ (Nd,Tm) [13]. Moreover, regarding the Lu-doped ceria system, even the composition having x = 0.8 was studied.…”

“…A gen preciated with increasing x for each system, but even mo smaller doping ions promotes the occurrence of larger given x. (2 ) for all the studied system while the ones of the Sm-and (Nd,Tm)-containing systems deri Lu-doped ceria are taken from [12]. Cell volumes of samples cr plied by 8 in order to make them comparable with those crystal Figure 6.…”

“…Trend of lnB 0 vs. ln(2V at ) for all the studied systems. Data of CeO 2 are taken from [88], while the ones of the Sm-and (Nd,Tm)-containing systems derive from [13]; experimental points of Lu-doped ceria are taken from [12]. Cell volumes of samples crystallizing in the F phase are multiplied by 8 in order to make them comparable with those crystallizing in the C structure.…”

“…An effective approach aimed at avoiding the experimental difficulties associated to the study of interfaces consists in the investigation of the high pressure behaviour of bulk samples to simulate the interfacial strain [10] and deduce the material compressibility. Following this idea, recently, several high pressure X-ray diffraction studies were performed by this [11][12][13] and other research groups [10] with the aim to determine the bulk modulus of several samples belonging to different RE-doped ceria systems, and finally to gain useful hints for the selection of the most proper compositions in the design of thin films.…”