**3. Investigation of Ce75Al25 − xGax (x = 0, 0.01, 0.1, 0.5, 1, 2, 4, and 6) alloys**

### **3.1 A comparative X-ray diffraction investigation of Ce75Al25 − xGax alloys**

**Figures 1** and **2** show the XRD patterns of Ce75Al25 − xGax alloys at different Ga concentrations. For the alloy with x = 0, the broad halo peak is found within the angular range 28–35**°**. This indicates the formation of homogenous glassy phase in Ce75Al25 alloy. While for the alloys with x = 2–6, broad halo peak is found within the angular range 39–50**°**. The unusual effect was seen in the XRD pattern on substitution of 0.01 at.% Ga. The second diffuse peak with higher intensity can be seen at higher-angle side. With increase in the quantity of Ga (x = 0.1, 0.5, 1, 2, 4, and 6),

#### **Figure 1.**

*XRD patterns of as-synthesized ribbons of Ce75Al25 − xGax alloys (x = 0, 0.01, 0.1, 0.5, and 1) (reprinted with kind permission from Ref. [25], copyright 2016, Elsevier).*

#### **Figure 2.**

*XRD patterns of as-synthesized ribbons of Ce75Al25 − xGax alloys (x = 0, 2, and 6) (reprinted with kind permission from Reference [27], copyright 2014, Elsevier).*

the positions and intensities of the higher-angle diffuse peak remains almost the same for different concentrations of Ga. The formation of additional diffuse halo peak on the higher-angle side in the XRD pattern due to addition of such sparse amount of Ga refers to unusual effect.

The prominent low-angle peak (~32°) with low intensity has been observed for x = 0 with respect to Ga addition. The formation of two amorphous phases for the alloys with x = 0.01–6 has been depicted from the two diffuse peaks with different intensities in the XRD patterns of Ce75Al25 − xGax alloys. It can be noticed that one hump is at its original position which indicates that the nature of short range order has not changed for pristine phase. The second diffuse peak appears at ~44<sup>o</sup> which indicates the significant change in the short range order. It may be pointed out that usually the hump in the XRD patterns for the large number of MGs occurs in the

**49**

**Figure 3.**

*Phase Separation in Ce-Based Metallic Glasses DOI: http://dx.doi.org/10.5772/intechopen.88028*

in Ti45Y11Al24Co20 metallic glass [54].

**alloys**

range of 26–38°. In the present case, the second hump is lying in the same range indicating that the SRO is very similar to the most common type of MGs. Similar observation of two humps has also been reported by Kim et al. for phase separation

**3.2 Comparative electron microscopic (TEM) investigation of Ce75Al25 − xGax**

*Bright-field TEM microstructures and the corresponding selected area diffraction patterns (shown in inset) of Ce75Al25 − xGax alloys with (a) x = 0, (b) x = 0.1, (c) x = 0.5, (d) x = 1, (e) x = 2, and (f) x = 4 (reprinted* 

*with kind permission from Reference [25], copyright 2016, Elsevier).*

The TEM image of Ce75Al25 depicts homogenous contrast, and its corresponding selected area diffraction (SAD) shows single diffuse halo ring (c.f. **Figure 3(a)**). After Ga substitution, the presence of two different amorphous phases having two different contrasts can be seen in **Figure 3(b–f )**. There is one type of amorphous phase which is dispersed in the matrix of other amorphous phase. **Figure 3(b–f )** displays SAD patterns with two diffuse halos after Ga substitution. The analysis of domain size dispersed in the amorphous matrix has been carried out, and the domain size variation with Ga addition has been done using *IMAGE J* software. The value domain size (in nanometer) increases linearly with Ga addition and then obtains a saturation value, i.e., ~7 nm at x = 4 and beyond. In **Figure 3(b–f )**, insets

#### *Phase Separation in Ce-Based Metallic Glasses DOI: http://dx.doi.org/10.5772/intechopen.88028*

*Metallic Glasses*

**Figure 1.**

**Figure 2.**

**48**

the positions and intensities of the higher-angle diffuse peak remains almost the same for different concentrations of Ga. The formation of additional diffuse halo peak on the higher-angle side in the XRD pattern due to addition of such sparse

*XRD patterns of as-synthesized ribbons of Ce75Al25 − xGax alloys (x = 0, 2, and 6) (reprinted with kind* 

*XRD patterns of as-synthesized ribbons of Ce75Al25 − xGax alloys (x = 0, 0.01, 0.1, 0.5, and 1) (reprinted with* 

The prominent low-angle peak (~32°) with low intensity has been observed for x = 0 with respect to Ga addition. The formation of two amorphous phases for the alloys with x = 0.01–6 has been depicted from the two diffuse peaks with different intensities in the XRD patterns of Ce75Al25 − xGax alloys. It can be noticed that one hump is at its original position which indicates that the nature of short range order has not changed for pristine phase. The second diffuse peak appears at ~44<sup>o</sup>

indicates the significant change in the short range order. It may be pointed out that usually the hump in the XRD patterns for the large number of MGs occurs in the

which

amount of Ga refers to unusual effect.

*permission from Reference [27], copyright 2014, Elsevier).*

*kind permission from Ref. [25], copyright 2016, Elsevier).*

range of 26–38°. In the present case, the second hump is lying in the same range indicating that the SRO is very similar to the most common type of MGs. Similar observation of two humps has also been reported by Kim et al. for phase separation in Ti45Y11Al24Co20 metallic glass [54].
