Title:
Synthesis method for obtaining the novel Mg2Si04-Pr60u nanocomposite material
Field of the Invention
The present invention relates to magnesium orthosilicate-praseodymium oxide (MgsSiCVPreOn) nanocomposite material, and in particular, to a method for the synthesis of magnesium orthosilicate-praseodymium oxide nanocomposite material following a simple approach and the idea to improve the optical properties and also to enhance the electrochemical properties of the prepared nanocomposite materials after mixing them with smaller amounts of polyaniline and activated charcoal in a proper weight ratio.
Background of the Invention
Magnesium orthosilicate (Mg2Si04) belongs to the most common and familiar olivine group of minerals. It possesses interesting properties like high melting point, high refractoriness, more resistant to hydration, very good chemical stability, low thermal conductivity, etc. It is an end member of the olivine solid solution series and is also found to be a most abundant mineral in earth. At room temperature, Mg2Si04 exists in the crystalline form, say in orthorhombic structure. In Mg2Si04 crystalline structure, the silicon (Si) atoms are interacted with four oxygen (O) atoms forming a tetrahedral bond and the magnesium (Mg) atoms present in between these tetrahedral bonds, which is the main reason to observe the interesting properties of Mg2Si04 as mentioned above. Mg2Si04 nanomateriat has recently drawn the attention of many researchers towards microwave, optical, device, biomedical, industrial applications, etc.
For instance, in the development of mobile communication, the specific kind of tunable microwave devices with low power consumption, multifunction capabilities and low

cost are essential. This can be achieved by mixing the ferroelectric ceramics having high permittivity (like barium strontium titanate) with the non-ferroelectric materials with low permittivity (for example, the oxides like MgO, Mg2SiC>4, Mg2Ti04, etc). Also, to modify the properties of Mg2SiC>4 nanomaterial and hence to utilize this material as-a microwave substrate material, one must decrease the densiflcation temperature which can be achieved by adding the oxides like B2O3, V2O5, U2CO3, etc. Among the various silicate-based minerals, Mg2Si04 can significantly contribute to optical applications, say tunable laser, long lasting phosphor, X-ray imaging, etc. For instance, it is found that the whenever the oxides are blended with the magnesium orthosilicate material or dopants are embedded into the magnesium orthosilicate material, there is a perturbation in the environment between the octahedral sites (Ml and M2 - representing the position of Mg ions) and the final composite or doped material can be used an excellent tunable laser in various spectral ranges. It is therefore realized that the physical properties of magnesium orthosilicate-based nanocomposites are significantly changed or enhanced. The present study mainly deals with the method for the synthesis of novel magnesium orthosilicate-praseodymium oxide (Mg2Si04-Pr60n) nanocomposite material and to investigate the optical and electrochemical properties. It is expected in the present study that the as-synthesized nanocomposite material will possess enhanced optical and electrochemical properties.
There are many methods like sol-gel, hydrothermal, combustion, sputtering, etc., for
the synthesis of pure (MgzSiOi), doped (for example, Cr, Fe, Mn, Zn, doped Mg2Si04),
and nanocomposite (for instance, Mg2Si04-B2C>3, Mg2Si04-CoFe204, Mg2Si04-Bao.4Sro.6Ti03, etc.) form of magnesium orthosilicate material. However, to the, best of our knowledge, there is no teaching of the synthesis procedure of Mg2Si04-Pr60n nanocomposite material and investigation of the non-linear optical properties and electrochemical properties of the same. In view of this, the main objective of this invention is to provide a simple

method for the synthesis of MgiSiC^-PrfiOn nanocomposite material having the enhanced optical and electrochemical properties.
Summary of the Invention
The present invention relates to a method of producing Mg2Si04-Pr60u nanocomposite material according to the following first to third aspects.
The first aspect is to provide a simple method for the synthesis of Mg2SiC>4-Pr60ii nanocomposite material using the precursors magnesium nitrate hexahydrate, tetraethyl orthosilicate and praseodymium oxide.
In the second aspect of the present invention, the structural investigation of pure Mg2Si04 nanopowder and Mg2Si04-Pr60n nanocomposite powder using X-ray diffraction (XRD) pattern by matching the XRD peaks with the JCPDS data and by calculating the average crystallite size, is provided.
The third aspect of the invention is to provide the clear idea on the optical properties of the samples by deriving the parameters like optical band gap, refractive index, extinction coefficient, optical conductivity, real and imaginary part of dielectric constant, volume energy loss function, surface energy loss function, linear susceptibility and non-linear susceptibility using UV-VIS absorption spectra.
In a fourth aspect of the invention, a simple method of fabrication of electrode using the as-synthesized samples and polyaniline (PANI) is provided to obtain the electrochemical performance of the samples using cyclic voltammetry measurement with the help of CH instrument.
The fifth aspect of the invention provides the results of the present study which can be used to prove that the novel material Mg2Si04-Pr60n chosen in the present invention is a potential candidate for the application of optical and electrochemical devices.

Brief description of the accompanying drawings
FIG. 1 is a flow chart of the method for producing magnesium orthosilicate-praseodymium
oxide nanocomposite material
FIG. 2 shows the X-ray diffraction (XRD) pattern of Mg2Si04 nanomaterial and Mg2SiO4 and Mg2Si04-PreOn nanocomposite respectively. The SEM images of the samples showed the existence of

nanosized particles with irregular agglomeration. From the SEM images, it was found that the agglomeration of particles was slightly larger in the case of Mg2Si04-Pr60n nanocomposite material.
The optical absorbances were used to determine the absorption coefficient and hence the optical band gap energy (Eg); the values of Eg were found to be 5.60 eV and 5.17 eV for the samples of Mg2Si04 and Mg2Si04-Pr60n, respectively. In the case of Mg2Si04, the value of Volume Energy Loss Function (VELF) is higher than that of Surface Energy Loss Function (SELF) at all possible energies. VELF and SELF derived from UV-VIS absorption spectra are maximum for smaller value energy, and they are approaching zero loss when the energy reaches optical band gap region. However, the situation is slightly different in the case of Mg2Si04-Pr60n where the SELF is greater than VELF. Form the variation of linear and nonlinear optical susceptibility of the two samples it can be noticed that that there is no reasonable change in the value of non-linear susceptibility of Mg2Si04. However, the variation of linear susceptibility of Mg2Si04- PreOn has several peaks in the lower energy region. There is a peak showing a maximum value of non-linear susceptibility appeared at 4.7 eV in the case of Mg2Si04-Pr60n. Hence, it is possible to achieve the non-linear optical nature of Mg2Si04-Pr60n effectively by neglecting the linear effects with the help of suitable polarizers if the incident light having the energy 4.7 eV or wavelength 264 nm is used. This result shows that the Mg2Si04-Pr60n nanocomposite material can be a suitable candidate for optically induced non-linear optical devices.
To evaluate the electrochemical performance of the Mg2Si04-Pr60n nanocomposite material, the samples were coated over the Mg foil and were under investigation^ follows. At first, the Mg foil was carefully polished and cleaned well with water and acetone. A paste obtained from the mixture of as-synthesized sample, activated charcoal (AC), polyaniline (PAN1) and ethylene glycol (EG), was applied over the surface of the foil (1><2 cm2). The foil

was then kept in hot air oven at 100 °C for 4 h. The completely dried foil was then used for further investigation with the help of electrochemical workstation. The sample coated Mg foil was used as the working electrode; Ag/AgCl and platinum wire were used as the reference counter electrode, respectively. The electrochemical characterization was done using the electrolyte of 0.5 M of KOH solution. The cyclic voltammetry analysis was made in the range from 1.5 to -1.5 V at various scan rates of 25, 50, 100, 200 and 300 mVs"1. It was observed from the results that the maximum specific capacitance of 1812 Fg-1 was observed at a scan rate of 25 mVs"1 for Mg2Si04-PreOn. From the results obtained from UV-VIS absorption spectra and cyclic voltammetry, it is found that the novel magnesium orthosilicate-praseodymium oxide (Mg2Si04-Pr60n) nanocomposite material synthesize using the method described in the present invention, possesses the enhanced non-linear optical and electrochemical properties compared to Mg2Si04 nanomaterial.