Influences of Incorporating AgNO3-BaTiO3 NPs on the Microstructure and Electrical Properties of PVA/PEO Polymers Matrix

INTRODUCTION
The (PVA/PEO) polymers are prominent materials in various medical, industrial, and electronic applications, because their unique properties including thermal stability, water solubility, and ease of shaping and processing [1]. Recent years have seen growing interest in enhancing polymer properties through the introduction of nanomaterials such as (AgNO₃) (BaTiO3), given their ability to improve polymers’ mechanical, thermal, and functional characteristics. These nanomaterials enhance structural stability, increase strength and durability, and improve electrical or thermal conductivity, thereby expanding the range of industrial, medical, and electronic applications for conventional polymers [2]. The (PVA) polymer prepared from the polymerization of vinyl acetate followed by alcoholysis. It has been widely used as films [3,4]. (PEO) is a hydrophilic, nonionic, water-soluble polymer that is used to deliver scaffold fabrication, drugs, and tissue engineering [5]. Polymers, blends, and composites have many novel properties, including: low cost, flexibility and high resistance, that make them particularly useful in various applications of electronic technique. Currently polymer science is a cutting-edge field due to the high strength, excellent corrosion resistance, and good thermal stability of polymers [6]. These materials are also characterized by their low cost, ease of processing, mechanical strength, and flexibility. Because of these properties, polymers have become essential components in many industrial applications, including microelectronics and photolithography. Composite materials have also emerged as important modern engineering materials due to their unique properties such as light weight and ease of assembly. These materials are widely used in electronic packaging for medical equipment, in aircraft manufacturing, and in the production of low-cost, lightweight polymer composites [7]. Currently composite materials refer to materials reinforcement surrounded by a weaker matrix material. The matrix serves to distribute the reinforcement and also to transmit the load to the reinforcement [8].  Composite nanomaterials are of great importance due to their unique physical and chemical properties. The interactions and fine dispersion of these particles within the polymer are key factors in developing the properties of these materials, such as their microstructure and electrical characteristics. [9,10]. In this research, the addition of nanoparticles to the polymers matrix increased the state of crystallinity. The A.c measurements showed that the dielectric constant and dielectric loss values are high at low frequencies consistent with previous studies Ref [11]. The main objective of this research is to analyze the effect of nano-particles on the microstructure and electrical characteristic of polymers blend to make them suitable for many use for example sensors, batteries, and active membranes.

MATERIALS AND METHODS
The materials used in this study were classified into two main categories: polymers and nanomaterials. The polymer components included polyvinyl alcohol (PVA) with a molecular weight of 14,000 g/mol, produced by BDH Chemicals Ltd (England), and polyethylene oxide (PEO) with a molecular weight of 3 × 10⁶ g/mol, produced by Cheng Du Micxy Chemical Co., Ltd. Both polymers are white, water-soluble, organic powders. The nanomaterials consisted of silver nitrate (AgNO₃) with a molecular weight of 169.87 g/mol, produced by a company in California, USA, and barium titanate (BaTiO₃) with a molecular weight of 233.19 g/mol, produced by Research Nanomaterials, Inc., Houston, Texas, USA.  Silver nitrate is a transparent, water-soluble inorganic compound, while barium titanate is a white, water-soluble inorganic substance.

Preparation of nanocomposite films
The sample (Ao, A1 and A2) was prepared by casting method with different weights as listed in Table 1. The step two was to dissolve the specified weights of polymers in DI water (H2O) using a magnetic stirrer at room temperature (21 °C) for (2 h) to obtain good solution. The solution was cast into a 6 cm Petri dish and dried (12) days in a dust-free environment.

Instruments used
The X-ray device using (Aeris-Malvern Panalytical) I = 7.5 kv, λ= 1.54 Å. FESEM analysis of the samples were measured using (Inspect F50-FEI company), 30.00 kV high voltage, and EDS measured using (Axia ChemiSEM- Thermo Scientific company) acceleration voltage 30 kV. AC analysis of the samples were measured using (LCR Meter).

RESULTS AND DISCUSSION
XRD analysis
In Fig. 1 showed the XRD results of pure (PVA/PEO) blend and the nanocomposite films of (PVA, PEO, AgNO3 and BaTiO3). The result of pure polymers shows semicrystalline nature, with high peaks at 2θ = 22.1°, 19.58°, and 23.59° these peaks correspond to the (133), (040) and (133) crystal structures of (PVA/PEO) blend as shown in Fig. 1a. The semicrystalline nature of these polymers plays a fundamental role in ensuring both chemical and electrochemical stability. Crystallization in polymeric systems generally proceeds through a hierarchical organization that spans multiple structural scales. Throughout this process, polymer chains undergo folding, leading to the formation of distinct lamellar structures characterized by specific molecular arrangements. This folded-chain configuration allows lateral growth in two dimensions while restricting chain propagation in the perpendicular direction, where structural imperfections are predominantly localized at the fold surfaces. While previous work [12] investigated the structural features of the pristine PVA/PEO blend withe spacific wights of nanoparticels, but the present study  usded the same pure sample (Ao) to compare, extends this analysis by examining the influence of modified weight ratios and the emergence of additional crystalline phases, the resule  consistent with those reported in previous studies [13]. However, this research presents a more comprehensive structural analysis, revealing improved ordering and the emergence of additional crystalline phases using new sample weight ratios. Fig. 1b, showed three high peaks at (2θ = 22.4°, 19.48°, and 23.59°) observed correspond to the (133), (040), and (133) crystal structures of polymers.  And other peaks were also showed as a result of adding nanomaterials. peak at (2θ = 31.82° and 39.77°) correspond to the (200) and (220) crystal structures of AgNO₃, the Braggs angle of (AgNO₃) agrees with JCPDS data (Code 96-210-5349), peak at (2θ = 31.82°, 45.48° and 56.42° ) correspond to the (110), (200) and (211) crystal structures of BaTiO₃, the Braggs angle of (BaTiO₃) agrees with JCPDS data (Code 96-152-5438). 
Fig. 1c shows peaks at (2θ = 22.17°, 19.5° and 23.35°) observed correspond to the (220), (131) and (025) crystal structures of PVA/PEO.  Peaks at (2θ = 31.57° and 39.69°) correspond to the (200) and (220) crystal structures of AgNO₃, and peaks at (2θ = 22.17°, 31.57°, 39.69°, 45.23°, and 56.17°) correspond to the (100), (110), (111), (200), and (211) crystal structures of BaTiO₃. Although some of the results are consistent with those reported in previous studies [14, 15] regarding the general behavior of the polymer, this study stands out for its novel scientific contribution in revealing the formation of additional crystalline phases not recorded in those studies, indicating a stronger interaction between the PVA/PEO mixture and the AgNO₃ and BaTiO₃ nanoparticles. In summary, the results of XRD show that more nanoparticles adding to the polymers blend leads to an increase in peaks. This is due to structural changes in the polymer matrix, which may result in alterations in the degree of polymer crystallinity and shifts in the arrangement of polymer chains. Several coefficients can be derived from the X-ray diffraction peaks, where the distance between crystalline planes (d) is calculated by Brag equation (1) [16]:

n λ = 2dsin(θ)                                         

Where n, λ, and (θ) mean the integer, wavelength, and angle of the X-ray respectively. The crystal size (D) is calculated by using Debye-Scherer formula (2) [17]:

D = kλ ∕ β cos(θ)     

k = 0.9 is the crystals factor, and (β) is full width at half the maximum of peak (FWHM), as shown in Table 2. The strain of lattice (Ɛ) is calculated by applied equation (3) [17]:

Ɛ = β ∕4tan(θ)                     

The size of crystal (D) was impacted and increased when add the (AgNO₃ and BaTiO₃) in matrix of polymer. Table 2 show important parameters of XRD measurements. 

Field-emission Scanning Electron Microscope (FESEM)
Field-emission Scanning Electron Microscope (FESEM) is a type of high-resolution microscope used to visualize very small topographic details on the surface or entire or fractioned objects [18]. FESEM is widely used in nanotechnology, and science of materials etc. where surface analysis and excellent of resolution are important [19]. The morphologies of the films were rigorously surveyed, examined, and studied in Fig. 2. 
The FESEM result of the pure polymers blend shows the morphology is smoother surface within some is rough surface and largely homogeneous due to its semicrystalline structure of polymers, as for the size particle (56.85 - 94.58) nm, as shown in Fig. 2a. AgNO₃ and BaTiO₃ The addition of nanoparticles contributed significantly to modifying the properties of the polymer matrix, which was characterized by uniform dispersion and granular structure without the appearance of obvious clumps. These particles appear spherical or sub-spherical and the particle size ranges between (33.03 - 43.78) nm as shown in Fig. 2b.
The increasing of loading of (AgNO₃ and BaTiO₃) revealed formalizing spherical shapes, the porous structure of the sample (A2) indicates its potential for applications requiring high surface area, such as sensors or electrochemical materials. Given that barium titanate (BaTiO₃) exhibits insulating properties, this enhances the sample’s potential for the fabrication of ionic conduction films or capacitors, The particles size range between (33.03 - 37.93) nm. The surface is more compact and the particle structure is clear as shown in Fig. 2c, The results indicate that AgNO₃ and BaTiO₃ particles are uniformly distributed within the polymers matrix, which can be explained by the compatibility between the polymer components and its ability to effectively contain the composite nanoparticles [20].

Energy Dispersive X-ray Spectrometry (EDS)
The (EDS) is used to analyze withe detect components to determine the chemical properties of films. Both oxygen and carbon appear as representatives of blend polymer [13]. The composition of elemental of polymer blend for (Ao) Fig. 3a showed the amounts of Carbon and Oxygen elements at 56.6% and 43.4% resistively. The EDS of polymers with nanoparticles films for (A1) Fig. 3b showed the C, N, O,Ti, Ag and Ba elements at the amounts of (46.3, 50.6, 0.1, 2.6, and 0.4) wt.%, respectively. EDS of PVA/PEO, AgNO₃ and BaTiO₃ films for (A2) Fig. 3c verified the existence of C, O, Ti, Ag and Ba elements at the amounts of  (36.4, 58.8, 1.4, 1.3, and 2.1)  wt.%, respectively.The data indicate that the high-intensity element is oxygen, which can be attributed to the polymer composition.

Electrical Properties (AC)
Dielectric constant and loss factors are the most convenient and efficient methods to investigate the structure of polymers. The electrical conductivity of insulating polymer can enhance by additive nanoparticles. Dielectric constant (έ) the ratio between the capacitance of a capacitor filled with a dielectric medium and that of the same capacitor when the region between its plates is a vacuum [21, 22].

έ = Cp/Co                                                                  

 
Where: Cp and Co are  vacuum capacitance parallel.
Figs. 4 and 5 shows that the dielectric constant and dielectric loss with variations frequency (f) that both have good-values at lower frequency, due to the nature that dipole moments have ample time in these zones to order themselves in the direction of the applied electric field. The dielectric constant and dielectric loss decrease monotonically and reach constant value as the frequency increases. 
The dielectric loss (ε ̋ ) determine by [23]:

ε ̋ = έ D                                                                       (5)

Where: D is coefficient of dispersion of nanoparticles.
With increasing frequency, the dielectric constant changes, the polarization of the space charge decreases, as a greater number of ions cannot diffuse in the direction of the applied electrical field, because the dielectric characteristics are low affected by charge carriers [22]. With increasing nanoparticles, the dielectric constant and loss decrease as a result of increased electrical conductivity due to increased charge carriers. [23, 24].
In Fig. 4 all samples (AO, A1 and A2) show a slight decrease in dielectric constant with increasing frequency. A2 has the highest dielectric constant value at low frequencies. Ao has approximately the lowest value. At low frequencies, the various polarizations (ionic, dipole, and intergranular) contribute significantly, resulting in a high dielectric constant value. By adding AgNO₃ and BaTiO₃  in (A1, A2), the sample’s polarizability increases, especially with A2 (which may have the highest concentration). At high frequencies, the polarizability decreases due to delayed charge movement, so the dielectric constant decreases.
Fig. 6 illustrates the variation of electrical conductivity as a function of frequency. The observed behavior can be attributed to interfacial polarization effects associated with A.C. conductivity, which progressively increases with increasing frequency. Furthermore, an enhancement in electrical conductivity was recorded with rising nanoparticle (NPs) content, likely due to the increased charge carrier density within the polymer blend matrix [24]. All samples show an increase in conductivity with frequency. A2 exhibit the highest conductivity values at most frequencies. Samples containing AgNO₃ and BaTiO₃ show improved conductivity due to the ionic conductivity of the silver nitrate and the high dielectric properties of barium titanate, which improves the polarization of the medium and the release of charges. Best performance in terms of conductivity and dielectric constant (A2). Best performance in terms of stability low loss A1.
The electrical conductivity was determine by [25]: 

σA.C = ω ε ̋ εo                                                             

CONCLUSION
The finding of the work showed that the adding of nanoparticles into matrix of polymers due to  develop the crystallinity. XRD measurement observed the higher peak at 2θ = 31.57° due to crystal planes of the BaTiO₃ lattice. New peaks showed at 2θ = 31.82°, 39.69°, 45.23° and 56.17° when nanoparticles was adding due to increasing crystallinity. Correspond (133), (040), (133), (110), (111), (200) and (211) crystal planes and others. Decrease in lattice strain were observed after adding nanoparticles to the polymer matrix. This is attributed to the improved crystallization process. The FESEM results confirm that the AgNO₃ and BaTiO₃ nanoparticles were uniformly distributed within the PVA/PEO matrix without obvious agglomerations, contributing to improved surface uniformity and density.  The porous structure of sample (A2) and the fine particle size ranging from (33.03 - 94.58) nm support the potential use of these films in nanodevice applications, such as sensors, ionic conduction films, and high-performance capacitors. EDS analysis showed a clear improvement in the composition of elemental of the polymer blend films after the addition of AgNO₃ and BaTiO₃ nanoparticles. The carbon content gradually decreased from 56.6% to 36.4%, and the oxygen content increased from 43.4% to 58.8%, indicating an increase in the oxide content in the surface structure.  The presence of Ti, Ag, and Ba elements at concentrations ranging from (0.1–2.6) % also confirmed the effective homogeneity of particle distribution within the polymer matrix. These results support the success of the nano loading process and the improvement of the structural properties of the films. The results of electrical properties indicate of the PVA/PEO films were affected by the presence of nanoparticles. Their incorporation increased the medium’s polarization and improved charge mobility, reflected in the higher conductivity and dielectric constant of sample A2 compared to the pure sample.  The insulating properties of barium titanate and the ionic conductivity of silver nitrate also contribute to improved overall electrical performance and reduced dielectric loss, making these films promising for highly efficient sensor and electrochemical device applications.

ACKNOWLEDGMENT
The authors gratefully acknowledge the support and guidance provided by the Department of Physics, College of Science, University of Babylon. They also thank Dr. K. Abdali and Dr. Huda Raad for their helpful contributions.

CONFLICT OF INTEREST
The authors declare that there is no conflict of interests regarding the publication of this manuscript.