Contents lists available at ScienceDirect Vacuum journal homepage: www.elsevier.com/locate/vacuum Effect of 40 MeV Li 3+ ion irradiation on dielectric and ferroelectric properties of (1-x)PVDF/(x)BaTiO 3 nanocomposites Mandakini Sharma, Anurag Gaur * , Jitendra Kumar Quamara Department of Physics, National Institute of Technology, Kurukshetra, India ARTICLE INFO Keywords: PVDF/BaTiO 3 nanocomposites Ion irradiation Dielectric properties Ferroelectric properties ABSTRACT The (1-x)PVDF/(x)BaTiO 3 nanocomposite films were prepared by solution mixing method. The dielectric con- stant (ε′) was increased by the BaTiO 3 incorporation in PVDF matrix. Further, the pristine PVDF and (1-x)PVDF/ (x)BaTiO 3 nanocomposite films were irradiated with 40 MeV Li 3+ ion beam from 15 UD Pelletron at Inter University Accelerator Center, New Delhi. The uniform irradiation effect is observed as the projected range values (calculated from SRIM-2008) are much larger than the sample thickness (∼0.06 mm). After irradiation, recrystallization and α→β phase transition were observed in PVDF. However, almost complete amorphization was observed in BaTiO 3 filler in (1-x)PVDF/(x)BaTiO 3 nanocomposite samples. After 40 MeV Li 3+ ion irradia- tion, the dielectric constant (ε′) and remanence polarization decrease for all the samples while, the coercive field increases. This is interesting to note that BaTiO 3 phase is amorphized through 40 MeV Li 3+ ion irradiation, which also causes to decrease the dielectric constant along with cross-linking effect in (1-x)PVDF/(x)BaTiO 3 nanocomposite films. 1. Introduction Polymer/inorganic nanocomposites have many application areas such as energy storage, pressure-sensors, EMI shielding, transducers, photoconductors, biochips and biodegradable scaffolds etc. [1–5]. The electrical properties of these composites depend on the weight fraction, shape and size of filler, polymer and filler interface etc. [6]. However, the electrical properties modification using swift heavy ion (SHI) irra- diation has been recognized as an alternate method for polymer com- posites [7,8]. Depending upon the energy of irradiated ions, the SHI interact with material via elastic (with nuclei of the target material) and inelastic (with electrons of the target material) collisions [9]. SHI lose most of their energy by excitation of electrons and ionization of atoms. Highly energetic ion beams interaction with polymer composites results in the formation of gaseous products accompanied by polymer cross- linking (i.e. formation of intermolecular bonds, ionization, and excita- tion), degradation (i.e. scission of bonds in the main polymer chain and in side chains, mass loss) etc. [10]. Moreover, the radiation effects on the physical and structural properties of dielectric materials are re- quired to study particularly, when such devices are being used in a radiation rich environment such as an insulator in nuclear radiation environment, in space as satellite electronics, in nuclear waste con- tainers and as missile guidance in military electronic systems [11,12]. Also, the dielectric materials having ion irradiation-induced uniform porosity can be used as a separator in supercapacitor application. The irradiation effect on electrical properties of polymer composites has been studied by many researchers [5,13–16]. However, no study on SHI irradiation effect on dielectric and ferroelectric properties of PVDF/ BaTiO 3 composites is available till date as per our knowledge. Instead, swift heavy ion irradiation induced modifications in PVDF [17–19] and BaTiO 3 [20–22] have already been studied separately. Therefore, this work represents a fundamental study of 40 MeV Li 3+ ion irradiation- induced modifications in the structural, morphological, dielectric and ferroelectric properties of PVDF/BaTiO 3 nanocomposites as compared to the un-irradiated samples. The post-irradiation α→β phase transition and crosslinking effect in PVDF matrix and amorphization in BaTiO 3 filler are observed and discussed in detail. 2. Experimental 2.1. Preparation of PVDF/BaTiO 3 nanocomposite film The barium titanate (BaTiO 3 ) nanoparticles were synthesized by co- precipitation method using barium acetate (Ba(C 2 H 3 O 2 ) 2 ; 99%) and titanium isopropoxide (TiC 12 H 28 O 4 ) as the starting materials. Poly (vinylidene fluoride) (PVDF, M.W. = 60000) is used as matix for the https://doi.org/10.1016/j.vacuum.2019.06.032 Received 13 May 2019; Accepted 25 June 2019 * Corresponding author., E-mail addresses: mansha.nitkkr@gmail.com (M. Sharma), anuragdph@nitkkr.ac.in (A. Gaur), jkquamara@yahoo.com (J.K. Quamara). Vacuum 167 (2019) 344–351 Available online 26 June 2019 0042-207X/ © 2019 Published by Elsevier Ltd. T