Table 2 Diffraction peak positions (2θ), miller indices (hkl), and calculated interplanar spacings (d, nm) for standards (ZnO & CuO) and synthesized samples (ZnO(Nd)/CuO & CuO(Nd)/ZnO).

From: Nd-doped CuO/ZnO and ZnO/CuO heterojunctions for simultaneous UV blocking and malachite green detoxification

h k l

2θ in deg.

d-spacings (nm)

hkl (ZnO)

hkl (CuO)

Standard-ZnO

Standard-CuO

ZnO(Nd)/CuO

CuO(Nd)/ZnO

Standard-ZnO

Standard-CuO

CuO(Nd)/ZnO

ZnO(Nd)/CuO

100

 

31.80

 

31.84

31.82

0.2814

 

0.2812

0.2814

 

110

 

32.56

32.34

32.80

 

0.2751

0.2730

0.2768

002

 

34.45

 

34.36

34.48

0.2604

 

0.2601

0.2609

 

−111

 

35.59

35.58

35.36

 

0.2523

0.2538

0.2523

101

 

36.29

  

36.24

0.2475

 

0.2479

 
 

111

 

38.79

38.84

38.76

 

0.2323

0.2323

0.2317

102

 

47.58

 

47.40

47.62

0.1911

 

0.1910

0.1918

 

−202

 

48.80

48.60

48.84

 

0.1866

0.1865

0.1868

 

112

 

51.45

51.48

  

0.1785

 

0.1775

110

 

56.66

  

56.64

0.1625

 

0.1625

 
 

202

 

58.41

58.36

58.42

 

0.1581

0.1580

0.1581

 

−113

 

61.63

61.74

  

0.1505

 

0.1507

103

 

62.92

  

62.86

0.1477

 

0.1478

 
 

022

 

65.90

   

0.1418

  

200

−311

66.46

66.34

66.20

66.58

0.1407

0.1410

0.1405

0.1414

112

−220

68.02

68.21

68.08

68.00

0.1378

0.1375

0.1379

0.1377

201

 

69.17

  

69.20

0.1358

 

0.1358

 
  1. The shift of diffraction peaks to lower 2θ angles in Nd-doped CuO or ZnO confirms lattice expansion caused by substituting smaller host cations (Zn²⁺: 0.074 nm; Cu²⁺: 0.069 nm) with the larger Nd³⁺ ion (0.098 nm)39,40. In contrast, peak shifts to higher 2θ angles suggest compressive strain from defect clusters41. For instance, in ZnO(Nd)/CuO, the ZnO (100) reflection at 31.80° shifted upward by 0.04° (tensile strain), while the CuO (111) peak in CuO(Nd)/ZnO shifted downward by 0.03°, indicative of compressive strain near Nd-induced vacancies42.
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