**3.1.2 Fourier Transform Infrared Spectroscopy (FT-IR)**

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Three other important parameters influence in the solvent evaporation rate and in the attainment of dense and continuous films: solution flow rate, nozzle distance and air pressure,. In this study, these parameters were kept constant, and their values were,

The YSZ films are amorphous, after deposition, and a heat treatment was required in order to stabilize the zirconia cubic phase. This heat treatment was performed at 700 °C for two

Two protocols were used for the film deposition: one-step deposition and multi-layer deposition. The first protocol consists in a deposition of 50 mL of precursor solution followed by heat treatment and the other protocol consists in a deposition of 150 mL of precursor solution in three sequential steps with intermediate heat treatment after each

The microstructure and the morphology of the films were evaluated by Fourier Transform Infrared Spectroscopy (FT-IR), X-ray diffraction (XRD) and Scanning Electron Microscopy

The spectrum of X-ray diffraction (Figure 4) shows that after the deposition, the film is

 

c or t ZrO2

Fig. 4. XRD spectrum of YSZ obtained from different precursor solutions before and after

before heat treatment

after heat treatment ethanol + propylene glycol

after heat treatment

after heat treatment

ethanol + 2-methoxy, 1-propanol

ethanol + diethylene glycol monobutyl ether

hours in a furnace with a constant heating rate of 2 °C.min-1 and slow cooling.

respectively, 35 mL.h-1, 250 mm and 3 kgf.cm-2.

deposition.

amorphous.

**3. Results and discussion** 

**3.1.1 X-ray diffraction (XRD)** 

**3.1 Microstructural characterization** 

heat treatment at 700 °C for 2 hours.

(SEM).

The FT-IR spectrum (Figure 5) shows a very pronounced peak around 471 cm-1 (zone IV). Comparing it to FT-IR spectra for cubic zirconia, presented in the literature (Khollam et al., 2001), it is possible to see the presence of vibrational frequencies resulting from metaloxygen bonds characteristic of this phase around 471 cm-1, revealing that the heat treatment at 700 °C allowed the stabilization of the zirconia cubic phase for the films prepared. The band located at 3455 cm-1 (zone I) can be attributed to bonds O - H, possibly due to the presence of solvent excess adsorbed in the film. The bands presented around 2330 cm-1 (zone II) correspond to adsorbed atmospheric CO2, according to (Andrade et al., 2006). In the region from 1630 to 1619 cm-1 (zone III), the bands correspond to asymmetric and symmetric stretch of COO-group (Farhikhte, 2010).

Fig. 5. FT-IR spectrum Of YSZ obtained from different precursor solutions after heat treatment at 700 °C for 2 hours.

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About YSZ Solid Oxide Electrolyte Deposition Direct on LSM Porous Substrate by Spray Pyrolysis 153

Fig. 7. (a) SEM image of the film obtained from ethanol and propylene glycol on the substrate at 350 °C, after heat treatment at 700 °C for 2 hours; (b) magnification of (a).

electrolyte, because it forms deep cracks and discontinuities.

On the other hand, the film formed (Figure 8b), is not continuous and suggests the overlapping of non-homogeneous rough boards, which are formed during the rapid evaporation of the solvent. This type of morphology is undesirable to use in SOFC

**(a) (b)**

Non-homogeneous rough boards

**(a) (b)**

Cracks increased

Fig. 8. (a) SEM image of the film obtained from ethanol and 2-methoxy, 1-propanol on the

After heat treatment (Figure 9), there seems to be a softening of the cracks seen after the deposition, possibly related to the contraction during the zirconia crystallization. Which, in this case, tends to reduce overlapping plates, softening the final morphological structure. However, this effect is not enough to homogenize the surface, and the cracks are not

The films obtained from ethanol and diethylene glycol monobutyl ether showed a considerable reduction in the amount of cracks and discontinuities (Figure 10a). After a soft scattering of the solution onto the substrate surface, the solvent evaporates properly, thus reducing internal stresses in the film and reducing the number of cracks, making it more

However, the magnification of the image (Figure 10b) revealed the presence of small cracks distributed throughout the film. These cracked regions jeopardize the homogeneity of the

substrate at 350 °C, without heat treatment; (b) magnification of (a).

completely eliminated (Figure 9b).

homogeneous (Neagu et al., 2006).
