Rietveld Refinement of Mg1-x
Nanoparticles Structure Synthesized by Sol-Gel technique
AnwarA. Muther1, Tagreed M. Al- Saadi2*
1,2College of Education for Pure Science/Ibn Al- Haitham, University of Baghdad, Baghdad, Iraq
Email: [email protected] Abstract
By Sol-Gel technique, Mg1-xNixnanoparticles (x =0, 0.05, 0.10, 0.15, 0.20, and 0.25) (NPs) were synthesized. Mg1-xNix nanoparticles were prepared by using magnesium nitrate Mg (NO3)2 .6H2O and citric acid C6H8O7. H2O. The nanoparticles obtained were characterized by X-ray powder diffraction (XRD), field-emitting electron microscopy (FE-SEM), and energy- dispersive X-ray spectroscopy (EDX). The crystal structure was studied by Rietveld analyzes.
Grain size was also calculated by using the Scherer and Williamson-Hall equation. The lattice constant of up to 4.204 Å -4.216 Å and the grains size were obtained from the Scherrer method 14.5nm-21.5 nm and from the Williamson-Hall method 11.2 nm-14.7 nm while it was in the range of 13.5 nm-18.92 nm FESEM test.
Keywords:Rietveld Refinement, Nanoparticles, Mg doped Ni, Sol-Gel, XRD Analysis
Nanotechnology has become at the forefront of the most important and exciting fields in the field of physics and other sciences, as it has given great hope for scientific revolutions in the near future that will change the direction of technology in many applications.
Nanotechnology can be attributed to the process of controlling and manipulating matter at the level of atomic dimensions, this control process is similar to engineering at the nanoscale level, and the process of nanofabrication is completely related to this engineering. The materials in the nanosphere give unique physical and chemical properties and properties.
Therefore, this phenomenon has been exploited in the production of materials, devices and systems unique in their properties, by controlling the shape and size of the nanosphere [1,2]
The importance of nanotechnology comes from its ability to work at these small levels, so its production of materials and devices is considered one of the smallest and most efficient things that have been made by humans since creation. Nanotechnology is specifically involved in science and engineering, such as active nanomaterials, nanoscale systems, biological nanoscale systems, and nanoscale biological medicine, and it has many promising applications and uses that will change many concepts. MgO Magnesium Oxide is a versatile oxidizing mineral due to its unique chemical and physical properties, as well as it has a high melting point (2852 ° C) so it has high temperature resistance (Refractory), and it can get Magnesium Oxide Mg0 in several ways, including: the colloidal solution method (Gel Sol), the pyrolysis spray (CSP) and the chemical vapor deposition (CVD) and others. The colloidal solution method is one of the best methods to obtain magnesium oxide (MgO), because it is easy to use, less expensive and can be The different sizes and shapes give the most oxides, and the size of the nanoparticles of magnesium oxide has a positive effect on the physical and chemical properties, including optical, magnetic, electrical and other structural properties, and there are factors that improve most of these properties, such as the temperature of calcination, concentration and the acid used as fuel [3,4].
Many researchers have been interested in preparing MgO nanoparticles due to its unique and new properties and its wide applications, as it is used as a catalyst in many chemical reactions as well as used in the process of coating metals to prevent rust and in the field of medicine,
manufacturing electronic circuits, sensors, electronic, chemical and mechanical engineering, as well as it has effectiveness It has a high level against bacteria, viruses and germs and that has a large surface area. Magnesium oxide has a cubic concentric structure (FCC) as and a lattice constant (a =4.212 nm) [5-7].
Magnesium-based materials have attracted a lot of interest to study hydrogen storage due to their advantages such as low cost and high capacity of magnesium .
Bulk nickel (Ni) is a ferromagnetic transition metal that naturally crystallizes in an fcc structure with a lattice parameter of 0.352 nm. Ni films are widely used in battery, electronics, aerospace industry applications, and chemical cells proper to their capability to resist high temperatures and corrosion .
The aim of this research is studying the crystal structure using the Rietveld refinement and morphologyof magnesium oxide doped with Ni ion.
2. Experimental procedures
Using Sol-Gel technique in preparing the nanocompound (Mg1-xNix) and the sample concentrations used were clearly as follows:
sample Mg (M) x content (M) Mg (g) x content (g)
0 0 1 10 0
1 0.05 0.95 9.49999 0.567
2 0. 10 0.90 9 1.134
3 0. 15 0.85 8.4999 1.701
4 0. 20 0.8 8 2.268
5 0. 25 0. 75 7.4999 2.835
Magnesium oxide nanoparticles were prepared using aqueous magnesium nitrate Mg (NO3)2
.6H2O and citric acid C6H8O7. H2O. As a solution of magnesium, nitrate was prepared by dissolving (10 g) of Magnesium nitrate in (15 mL) of deionized water. According to the molarity then prepare the solution by dissolving (1.4 g) of citric acid in (15 ml) with a molar calculation mix the two solutions in a beaker Heat resistance by stirrers Magnetic for (40 min) degree at room temperature to ensure the two solutions are completely homogeneous.
Thereafter adjusting the pH by means of an exponentiation scale the pH is close to (7) by adding an ammonia solution (NH4 (OH)) in the form of drops, and it is placed the resulting solution is on the magnetic stirrer with the heating element turned on and lifted Temperature to (90C).
For evaporation of the water as the solution continues to be stirred and during its escalation gases. The color of the solution turns into a yellowish-white until the solution begins to turn into a white gel from the color. Then reduce the temperature to (40C) and the temperature is raised gradually and for a period of time it starts the jelly was ignited to form a dry gel (xerogel).After that ground with a pestle mortar. The resulting powder is placed in a heat- resistant container in an oven for calcination by degree (700°C) temperature for two hours.
3. Results and Discussion 3.1.Structural properties
The structural properties of the prepared samples were studied using the technique of X-ray diffraction (XRD). The device used was of the type (Philips PW1730) the X-ray emitter of the type (Cu-kα1), the wavelength (1.54Å) its voltage (40kV) and the current (30mA). By comparing the results and data obtained with the international standard cards (JCPDS) the surface formation of the samples was also studied using a scanning electron microscope (SEM)
The unit cell size (V) was calculated using the following equation:
V=(a)3 ………. (1) Where a= the lattice constant
By X-ray diffraction pattern, the structural phase of MgO was determined and the results shown in table 1. The XRD patterns of the samples were recorded to get the results. As shown in Figure 1, the diffraction peaks observed are associated with , , , , and  respectively.
It is one of the methods that can be used to extract the information and determine the parameters of the unit cell from the diffraction angle. It helps explain the model of the X-ray diffraction spectrum by using specific software for that purpose, including disposal based on analysis Rietveld which can develop the crystal supposed to be work it is necessary to filter the structural features, but they cannot add new information to information that is not equipped with a standard. The visualization of the suitability between the spectrum in the neighborhood, the observation, and the computation, and it is possible to know the success of the disposal process, as well as the fact that it helps in the rest of the environment. Assigning new refinement parameters that lead to good suitability that work on improving the model and assumption model to calculate the intensity and to single-phase and approximate it with an analytical term that includes the effects of measuring devices and structural parameters .
yci=S ƩkLk │F│2 ɸ (2θi -2θk ) Ok A +ybi ………..(2) Whereas:
S: The scale factor
(yci): The intensity computed at point (i) and point (i) take values from 1 to several thousand of the stair scan representing (∆2θ)
K: represents the Miller indices (hkl) for a Bragg’s reflection
Lk : Includes Lorenz factors, polarization, and a multiplicity limit that depends on symmetry.
ɸ: Reflection function of the profile.
Ok: The preferred orientation function for the non-ideal (non-random) distribution
A: The absorption factor that depends on the thickness of the sample and on the geometry of the diffraction (in the Bragg-Brentano diffraction pattern it is a constant across the spectrum and is contained in the scaling factor)
ybi: The value of back intensity for a number ith of data points
The “fullprof” software includes factors of reliability (R) or what is sometimes called the Agreement. The criterion that will be set in the judgment on the quality of the refinement process, given the choice to give clear indicators to follow the refinement process. These factors are given as follows:
- The reliability factor of the profile
Which is given by the following relationship:
Rp =Ʃi │yoi –yci │\ Ʃiyoi ………(3) - the weighted profile reliability factor
Which is expressed as it comes:
Rwp =Ʃi Wi(y –y)2 \Ʃiyoi ………(4) - Expected reliability factor
If the background intensity is high, then the value of (Rwp) becomes large automatically and to obtain an ideal value then (Rwp) must be close to the expected reliability factor, which is expressed in the following relationship:
Rexp =[(N-p)\ƩWi yoi2
Whereas:N: number of points in the observed powder diffraction spectrum
P: The number of parameters being refined
The values of (Rexp) reflect the quality of the data used. Therefore, the ratio between (Rwp) and (Rexp) represents the quality of the suitability process, which is expressed as follows:
If the data is of high quality, then the value of (Rexp) will be small and the value of X2 upon completion of the refinement process will be greater than the number (1).
- Reliability factor of Bragg (RB)
It is sometimes called the reliability factor Bragg density and is expressed in the following relationship:
Table (1) the values of (a) unit cell and volume (V)
Table (2) the values of reliability factors
Sample Unit cell (a) V(a)3
0 4.216 74.95234
1 4.215 74.8857
2 4.208 74.5307
3 4.204 74.3051
4 4.207 74.4909
5 4.213 74.7914
sample Rp Rwp Rexp X2
0 21.7 19.9 10.12 1.96
1 20.3 23.3 7.93 2.93
2 19.9 18 8.29 2.17
3 27.1 19.8 9.92 1.99
4 20.3 18.9 7.71 2.45
5 41.7 43.5 7.48 5.81
Figure (1) Rietveldrefinement by using fullprofsoftwre
The lengths of the bonds between magnesiumand oxygen atoms were also calculated by using the PowderCell software (PCW23)  and as shown in the table (3). It is noted that the bond length decreases because the ionic radius of nickel is (82 pm) is less than the ionic radius of magnesium which has (86 pm).
Table (3): The lengths of the bonds between silver atoms No atom1 atom2 Quant.
Bond Length (Å)
0 1 2 3 4 5
1 Mg Mg 54 2.1081 2.1075 2.1060 2.1042 2.1038 2.1020 2 O O 36 2.9814 2.9805 2.9783 2.9758 2.9752 2.9728
3.3.The crystallite size
The crystallite size was calculated using the Scherrer's formula in X-ray diffraction:
DSh=Kλ\βcosθ ……….(8) K=shape factor about (0.9)
λ =wave length (0.154nm)
β=Full Width at Half Maximum (FWHM) (rad) θ=Bragg angle (rad)
The crystallite size was also calculated using the Hall-Williamson equation (DW-H) which takes into account micro strain of the crystal lattice :
βcos θ = K λ\DW-H +4ε sin θ ………(9) ε= the strain
y = -0.003x + 0.010
0.0078 0.008 0.0082 0.0084 0.0086 0.0088 0.009 0.0092 0.0094
0.3 0.5 0.7
y = -0.002x + 0.010
0.009 0.0091 0.0092 0.0093 0.0094 0.0095 0.0096 0.0097 0.0098 0.0099 0.01
0.3 0.5 0.7
y = -0.004x + 0.010
0.007 0.0075 0.008 0.0085 0.009
0.3 0.4 0.5 0.6 0.7
y = -0.008x + 0.012
0.005 0.0055 0.006 0.0065 0.007 0.0075 0.008 0.0085 0.009 0.0095
0.3 0.5 0.7 0.9
4 5 2 3
Figure (2): The Williamson-Hall plots
The difference between the grain size calculated according to the Williamson-Hall method and the grain size calculated according to the Scherrer formula is attributed to the fact that the Williamson-Hall method takes into account the strain due to the defects and distortions in crystal, which contributes to the broadening of the peaks. A negative value for the strain means lattice shrinkage.On the other hand, it can note from the table that the particle sizes are within the nanoscale of all the prepared samples.Table (4) the values of the crystallite size and the strain according to Scherrerand Williamson-Hall equations.
Table (4): The grain size (D) and strain (ԑ) according the Scherrer and Williamson-Hall equations
Sample DSh(nm) DW-H(nm) ε
0 16 13.3 -9.25
1 14.5 13.0 -5.5
2 17 13.3 -1.15
3 20.2 11.5 -2.025
4 19.5 14.7 -7.5
5 21.5 11.2 -1.975
3.4.Determination of Texture coefficient
Texture coefficientis used to describe the predominant direction of plane growth in the crystal. If (TchkL> 1), it indicates the growth trends of the preferred plane in the crystal, and when the value of (Tchkl =1) This indicates the ideal state of plane growth, but if it is (0<Tchkl<1), this indicates a multiplicity of crystallization in non-uniform directions and can be calculated using the Harris method [15, 16]
TC=I(hkl)/Iο(hkl)\NP-1∑I(hkl)/Iο(hkl)……… (10) N: The number of peaks apparent in the X-ray diffraction I: the measured relative intensity of the plane (hkl).
Iₒ : The measured intensity of the plane (hk1) taken from the (JCPDS) card.
y = -0.003x + 0.009
0.0074 0.0076 0.0078 0.008 0.0082 0.0084 0.0086
0.3 0.5 0.7
y = -0.007x + 0.012
0.007 0.0075 0.008 0.0085 0.009 0.0095 0.01
0.3 0.4 0.5 0.6 0.7
Table (5):The values of the Texture coefficient (TC) Sample Tc (111) Tc
Tc (220) Tc (311) Tc (222)
0 1.887 0.734 0.806 0.821 0.751
1 1.772 0.668 0.755 0.712 0.638
2 1.827 0.491 0.565 0.579 0.537
3 1.595 0.442 0.566 0.693 0.529
4 1.5702 0.3886 0.4393 0.6412 0.4368 5 1.6855 0.5343 0.6080 0.9895 0.0587
Results that have been obtaining it for the prepared samples is shown in Table No. (), as it was noticed that the texture factor is close to the one for the main peak (111) with preferred orientation of the Magnesium Oxide nanoparticles prepared at along the diffraction plane (220) and a slight lack of growth along the plane (222).
3.5.Field Emission Scanning Electron Microscopy (FESEM)
The morphological characteristics of the Ag1-xCux sample were studied using FE- SEM analysis. It can observe from Figure (4) spherical or spherical nanoparticles with some agglomeration, which may be due to the limited energy analysis of FE-SEM. It was found from the images that the size of the grains of the sample (Mg1-xNix) ranged between (26-38 nm). In FESEM, the particle size was calculated by taking the remarkable grain boundaries.
Whereas in XRD, the measurements are taken from a crystalline region that deflects X-ray waves . Thus, the particle size measurement of (Mg1-xNix) using XRD was found to be smaller than that of SEM.
Figure (3) the scanning electron microscope image of sample 5 in a different scale
3.6.Energy - Dispersive X - ray Spectroscopy(EDX)analysis
It is an analytical technique used to find out the type of chemical elements present in the sample. The principle of this technique depends on the mutual effect between the electronic beam emitted from the device fuse and the sample material. In addition, since each substance has a distinct atomic structure, it has a distinct set of peaks in the X-ray spectrum, and for X-
rays, when the accelerated electrons fall on the atoms of the target substance. These electrons extract one of the atom's electrons from the inner orbitals of the target and an ionization state occurs, or the electron may rise to a higher energy orbital and get excited. In both cases, the atom is trying to reach a state of stability. When the electron moves from a higher energy orbit to a lower energy orbit, the moving electron emits a photon of energy equal to the energy difference between the atomic orbitals. That the energy difference is characteristic of each chemical e There are a number of permissible transitions between atomic orbitals symbolized by (Lα, Kα) .
As a result, EDX showed the presence of Mg and O peaks of the emergence of Mg and O with the emergence of other distinctive peaks belonging to the element nickel. The evidence indicates that the sample does not contain any other element and is, in fact, free from other impurities.
Figure (4): EDX characteristic spectrum obtained from sample 5.
Mg1-xNixnanocomposite particles were obtained by sol-gel method. Whereas, citric acid acts as the ignition agent to obtain the nanocomposite. The nanoparticles were characterized by X-ray diffraction, FESEM and EDX. Tests proved that the prepared powders are within the nanoscale range and that the compound possesses a face-centered cubic structure.
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