Physica E 120 (2020) 114058 Available online 2 March 2020 1386-9477/© 2020 Elsevier B.V. All rights reserved. Defect dipole polarization mechanism in low-dimensional europium substituted Al 0.8 La 0.2 TiO 3 nanostructures S. Dastagiri a , M.V. Lakshmaiah a, ** , K. Chandra Babu Naidu b, * a Dept. of Physics, Sri Krishnadevaraya University, Anantapuramu, 515003, A.P, India b Department of Physics, GITAM Deemed to be University, Bangalore, 562163, India A R T I C L E INFO Keywords: Nanostructure Low-dimensional systems Optical spectra Electronic properties ABSTRACT Low-dimensional Europium substituted Al 0.8 La 0.2 TiO 3 (Al 0.8 Eu y La 0.2-y TiO 3 (y ¼ 0.01–0.04))/AELTO nano- structures were prepared via hydrothermal method. The X-ray diffraction (XRD) patterns revealed the mixed phase (tetragonal and orthorhombic) structure of AELTO. Furthermore, the surface morphology evidenced the formation of AELTO nanostructures. The wide optical band gap (E g ) was achieved for y ¼ 0.01–0.04 contents and found to be varying from 3.371 to 3.399 eV. The high dielectric constant (ε 0 ) values of 2.84 � 10 8 at 10 kHz and 101608.8 at 1 MHz were obtained for y ¼ 0.02 at room temperature due to defect dipoles. In addition, the high ac-electrical conductivity (σ ac ) of 15.78 S/cm (at 10 kHz) was observed at room temperature. The frequency dependence of dielectric modulus and impedance parameters was elucidated. The reverse arc present in the Cole- Cole plot of y ¼ 0.02 content clearly suggested the presence of defect dipoles in AELTO. 1. Introduction Perovskites are the ceramic materials which offered potential ap- plications in the feld of science and technology. In view of this, different perovskite structures in bulk and nano form exhibited extensive appli- cations in charge stored capacitors, supercapacitors, electrodes, piezo- electric devices, ferroelectric devices, micro-electromechanical system (MEMS), magnetocaloric devices, multiferroic devices, photocatalysis, ultrasonic transducers, actuators, sensors, electromagnetic shields, mi- crowave absorbers, dielectric absorbers, relaxors, memories, antennas, biomedical devices, magnetic hyperthermia, electrochemical devices etc., [1–24]. Among all perovskites, the lanthanum titanate (LaTiO 3 ) is one of the best ceramic materials exhibiting the signifcant electrical properties [25]. In addition, the LaTiO 3 based materials (in bulk, nano, polymer, thin flm, & composites) such as silver, copper, gold, nitrogen, strontium, barium and calcium substituted LaTiO 3 were synthesized and analyzed for various structural, electrical, magnetic, physical, ferro- electric, optical, piezoelectric and chemical properties [26–37]. However, in the literature [38–58], it was reported that the rare-earth/trivalent substituted titanate based materials exhibited the formation of defect dipoles. In general, this mechanism can be treated as an intrinsic property of the some perovskite structures. If the rare-earth/trivalent element is doped to the titanate based ceramic material, the oxygen vacancies will be created in order to compensate the charge. These oxygen vacancies can in turn lead to the formation of defect dipoles. Zhao et al. [7], described that the defect dipoles were mostly observed in the case of perovskite structures exhibiting the phase transition from either orthorhombic to tetragonal or rhombohedral to tetragonal. The defect dipoles among these kinds of perovskite struc- tures can favour the rotation of domains and then polarization. At this moment, if the external electric feld is applied to the perovskite mate- rial consisting of defect dipoles, these defect dipoles will be consistently aligned in the direction of the electric feld through the oxygen va- cancies and migration. As a result, the nano-domains will be grown into larger number of domains. Therefore, these defect dipoles will induce the rotation of domains and further increase the polarization of material to larger extent. Recently, a research team [60] prepared the high dense Al x La 1-x TiO 3 (x ¼ 0.2–0.8) (ALTO) nanospheres via the hydrothermal method and reported the induced dielectric behavior of all samples. In particular, the x ¼ 0.2–0.8 contents showed the decreasing trend of dielectric constant from 302.1 to 14.8 (at 100 kHz). This was obtained as a result of decrease of density of x ¼ 0.2–0.8 contents from 11.210 to 7.738 g/cm 3 respectively. In addition, the wide optical band gap (E g ) values ranging * Corresponding author. ** Corresponding author. E-mail addresses: drmvl2009@gmail.com (M.V. Lakshmaiah), chandrababu954@gmail.com (K. Chandra Babu Naidu). Contents lists available at ScienceDirect Physica E: Low-dimensional Systems and Nanostructures journal homepage: http://www.elsevier.com/locate/physe https://doi.org/10.1016/j.physe.2020.114058 Received 19 January 2020; Received in revised form 20 February 2020; Accepted 28 February 2020