*3.3.1 XRD for La, Gd substituted Zn0.95Co0.05O nanostructure*

The Zn0.95Co0.05O (ZCO5), Zn0.92Co0.05La0.03O (ZCLO53) and Zn0.92Co0.05Gd0.03O (ZCGO53) nanostructures were synthesized by a sol-gel process [11]. The structural information of La and Gd doped ZCO5 nanostructure using the Rietveld method for XRD pattern of wurtzite structure (space group P63mc) refined and shown in **Figure 8(a)**. The miller indices of wurtzite structure (100), (002), (101), (102) and (110), respectively, observed with diffraction angle 2θ = 31.88, 34.49, 36.34, 47.59 and 49.65° of ZnO. The XRD peak intensity of Zn0.95Co0.05O is reduced with La and Gd doping into it. This is because the ionic radii of La3+ and Gd3+ ions is much larger than TM Zn2+ and Co2+ ions, which results into lattice deformation of ZnO. Due to this, the lattice parameters such as lattice distortion, Zn–O bond length/angle and per unit cell volume are affected to induce lattice defects. The value of lattice constant, *a* = 3.252(1) Å, 3.253(2) Å and 3.255(1) Å, *c* = 5.204(1) Å, 5.218(3) Å and 5.212(3) Å, V = 47.660(1) Å3 , 47.818(3) Å3 and 47.823(2) Å3 , and χ2 = 3.37, 0.893 and 2.9, respectively, extracted for ZCO5, ZCLO53 and ZCGO53. It is also reported that the average value of particles size, D of nano-aggregation is 142 and 86 nm, respectively, for ZCLO53 and ZCGO53 [12]. The wurtzite ZnO structure and lattice defects (vacancies/interstitials) are also found with Raman study. Photoluminescence spectra have near band edge emission (shown energy band gap, Eg = 3.26 eV for ZCLO53 and for ZCGO53, Eg = 3.27 eV) and the defects/

#### **Figure 8.**

*(a) XRD pattern of Co, La and Gd doped ZnO nanostructure. (b) TEM image of Zn0.94Fe0.03Ce0.03O nanoparticles. (c) Raman spectra of pure and low Co concentrated ZnO nanoparticles. (d) Photoluminescence (PL) of Ni, Cu, Ce substituted ZnO nanoparticles. Adopted from Refs. [10, 11, 57, 58].*

**107**

*Ferromagnetism in Multiferroic BaTiO3, Spinel MFe2O4 (M = Mn, Co, Ni, Zn) Ferrite…*

Gd doping into Zn0.95Co0.05O, is confirmed with ZFC/FC magnetization.

VO evolution with variation in visible PL spectra. The Zn0.95Co0.05O nanoparticles are paramagnetic at room temperature and involved superparamagnetic transition at low temperature. The antiferromagnetic interactions are enhanced with La and

The DMS ZFCeO nanoparticles were synthesized by a sol-gel process [57]. **Figure 8(b)** shows the TEM image and the average particles size, D, of nanoparticles is 97 ± 4 nm. The inset of TEM is the HRTEM to show the crystalline formation and lattice spacing after doping into ZnO. It can be noted that the distorted lattice has an enhanced interplanar spacing *d* [corresponding to (101) planes] ~ 0.247 nm. For pure ZnO, the value of *d* ~ 0.237 nm. In HRTEM image, some little spots that covered the lattice fringes of spacing are also observed. This is an indication towards

The Zn1 − xCoxO [*x* = 0.002 (ZCO02), 0.004 (ZCO04), 0.006 (ZCO06) and 0.008 (ZCO08)] nanoparticles were synthesized by a sol-gel process [58]. The XRD pattern results into wurtzite ZnO structure. The ZnO with Co doping has nanorods type morphology with diameter, D (nm) = 18 ± 2, 23 ± 3, 41 ± 5 and 53 ± 3, and length L (nm) = 39 ± 3, 57 ± 5, 95 ± 3 and 127 ± 5, respectively, for ZCO02, ZCO04, ZCO06 and ZCO08. **Figure 8(c)** shows Raman vibrational modes, which are located

E2(high) and (2B1 low; 2LA) phonon modes, respectively [59]. The sharpest and

mode, E2(high), involved motion of oxygen, which is the characteristic of wurtzite lattice. With increasing Co concentration, a pronounced weakening in peak height, E2(high) mode, than pure ZnO, has been observed. The intensity of E2 mode of pure ZnO is shifted towards lower frequencies with increasing Co doping. This happens because decreasing binding energy of Zn-O bonds and a tensile strain in nanograins. An additional strong peak known as additional mode (AM) is

mode is the quasi-longitudinal optical mode formed with abundant shallow donor defects (Zn interstitial, oxygen vacancies, etc.). It is also reported in Ref. [59] that the RTFM is enhanced in low Co concentrated ZnO nanoparticles due to lattice defects. The low temperature ZFC/FC magnetic measurement indicates long-range

The Zn0.95Ni0.05O (ZNiO), Zn0.91Ni0.05Ce0.04O (ZNiO:Ce), Zn0.95Cu0.05O (ZCuO) and Zn0.91Cu0.05Ce0.04O (ZCuO:Ce) nanoparticles were synthesized by a sol-gel process [10]. **Figure 8(d)** show the PL emission for Ni, Cu, Ce substituted ZnO nanoparticles at room temperature. The peak at 369 (3.36 eV) is correlated with surface exciton recombination, which is the near band edge emission of ZnO [59]. The visible emission is formed due to radiative recombination of a photogenerated hole for which an electron occupied oxygen vacancies. The violet emission at 426 nm is the effect of radiative defects related oxygen and Zn vacancies. The peak at 461 and 484 nm is the blue emission, which have two defect level formed due to transition from Zni to valance band or bottom of the conduction band to O interstitial. The peak at 632, 661 and 673 nm is the red emission formed with intrinsic

attributed to E2(high)-E2(low), A1(TO),

can be attributed to nonpolar high frequency

whose intensity is increased with Co concentration. This AM

*DOI: http://dx.doi.org/10.5772/intechopen.82437*

*3.3.2 TEM of Zn0.94Fe0.03Ce0.03O (ZFCeO) nanoparticles*

ferromagnetic clusters or structural inclusions formation.

*3.3.3 Raman study evaluated lattice structure inducing defects*

antiferromagnetic-ferromagnetic ordering to form BMPs.

*3.3.4 Photoluminescence spectra extract ZnO lattice defects*

at around 314, 368, 422 and 533 cm<sup>−</sup><sup>1</sup>

strongest peak at about 422 cm<sup>−</sup><sup>1</sup>

observed at 554 cm<sup>−</sup><sup>1</sup>

VO evolution with variation in visible PL spectra. The Zn0.95Co0.05O nanoparticles are paramagnetic at room temperature and involved superparamagnetic transition at low temperature. The antiferromagnetic interactions are enhanced with La and Gd doping into Zn0.95Co0.05O, is confirmed with ZFC/FC magnetization.
