Vol:.(1234567890) Journal of Materials Science: Materials in Electronics (2020) 31:9212–9223 https://doi.org/10.1007/s10854-020-03452-1 1 3 Tailoring efect of large polaron hopping in the conduction mechanism of Ca‑modifed BaTiO 3 system Supriya Bisen 1  · Mehjabeen Khan 1  · Ashutosh Mishra 1 Received: 4 November 2019 / Accepted: 21 April 2020 / Published online: 2 May 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020 Abstract Tailoring efects of Ca-doping concentration on the structural, optical, and electrical properties of Ba 1−x Ca x TiO 3 (x = 0.0 to 0.15) nanomaterials prepared via low-temperature sol–gel auto combustion technique are presented. XRD results reveal that all the prepared nanomaterials are crystallized in tetragonal structure with space group P4mm. FT-IR measurements are carried out in order to reveal the vibrational frequencies of bonds in the crystal lattice. A strong absorption peak due to Ti–O bond (TiO 6 octahedron) appears at 538 cm −1 that shifts to a higher frequency with an increase in the doping of Ca ions. It is explained by the Coulomb interaction. Optical band gap of the sample increases with increase Ca doping as 3.44 eV (x = 0.0), 3.48 eV (x = 0.10), and 3.45 eV (x = 0.15). The BCT materials with x = 0.10 apparently show that the particle with short-range order can strongly infuence the formation of intermediate states in the gap. Dielectric behavior is found gov- erned by the interfacial polarization, whereas the ac conductivity supports the non-Debye process [n < 1] that is described using Jonscher’s power law. The conduction mechanism is found changing from small polaron to large polaron hopping as the Ca ions increase. Moreover, the electrical conductivity arising due to the movement of charged ions is correlated with the hopping and the lattice defects. The temperature-dependent activation energy is obtained in the range of 0.19–0.12 eV, which evidences the NTCR behavior observed for all studied materials. 1 Introduction Perovskite type (ABO 3 )–BaTiO 3 oxide materials are having their physical properties such that they fnd various appli- cations in ferroelectric memories as surface acoustic wave device, micro-electromechanical systems, tunable microwave flters, and microwave capacitors [1]. In the last few dec- ades, the optical and electrical properties of some relaxor ferroelectrics have been widely interrogated for application in wireless communication, metal–oxide–semiconductor, microwave dielectric, and feld-efect transistor (FET) [2–6]. Barium titanate (BaTiO 3 ) is an industrially important com- pound that exhibits ferroelectric properties at and above room temperature. It has fve diferent crystallographic forms: hexagonal, cubic, tetragonal, orthorhombic, and rhombohe- dral. The hexagonal and cubic structures are paraelectric in nature while tetragonal, orthorhombic, and rhombohedral show ferroelectric behavior in nature [7–9]. The research for a suitable photo-electrode and photo-catalyst, perovskite- based metal oxides (ABO 3 ) has been the subject of extensive studies during the past two decades [10–12] because they ofer a wide range of possibilities for tailoring their struc- ture through cationic substitutions either at A or B sites in order to tune their optical and electrical properties [13]. In Ba 1−x Ca x TiO 3 (BCT), a widely accepted view is that a ran- dom feld-induced ferroelectric domain state may be respon- sible for the observation of relaxor behavior. Nevertheless, it is ensure even if Ca 2+ ions can cause Ca 2+ –V o centers to form dipoles and thus set up a local random electric feld [14, 15]. For both fundamental and commercial importance, enormous eforts have been pursued to modify the dielec- tric and ferroelectric properties of BaTiO 3 -based materials by A-site substitution. It comes from alkaline-earth (Sr 2+ or Mg 2+ ) and rare-earth ions (La 3+ , etc.) and their cation size efects that cover up Ti of-centering hence the lower Curie temperature. On the other side, the efects of Ca-substitutions in BaTiO 3 are entirely unique and increasing interest has been received recently [16]. In recent years, the sol–gel technique has gained interest in the area of processing of nanomateri- als, microstructure because of its several advantages such * Supriya Bisen sbisen.sop@gmail.com 1 Material Science Lab, School of Physics, Vigyan Bhawan, Devi Ahilya University, Takshshila Campus, Khandwa Road, Indore 452001, India