Contents lists available at ScienceDirect Ceramics International journal homepage: www.elsevier.com/locate/ceramint Defect driven d 0 ferromagnetism and colossal dielectric behavior in Bi (Zn 0.5 Ti 0.5 )O 3 –PbTiO 3 ceramics Manasmita Mishra a , Yajun Zhang b , Debabrata Mishra c , M.P.K. Sahoo a , P.K. Pradhan d , A.K. Pattanaik a,* a Department of Physics, Veer Surandra Sai University of Technology, Burla, 768018, India b Theoretical Materials Physics, Q-MAT, CESAM, University of Liège, B-4000, Liège, Belgium c Department of Physics & Astrophysics, University of Delhi, Delhi, 110007, India d Department of Mechanical Engineering, Veer Surandra Sai University of Technology, Burla, 768018, India ARTICLE INFO Keywords: Ceramics Solid state reactions Sintering Microstructure Dielectric response Magnetic measurement ABSTRACT We report room temperature ferromagnetism and colossal dielectric behavior in non-magnetic polycrystalline samples of x (BiZn 0.5 Ti 0.5 O 3 ) – (1-x) (PbTiO 3 ) with x = 0.25, 0.50. These samples are synthesized by mechanical alloying followed by heating the samples at elevated temperatures. Room temperature X-ray diffraction study reveals the formation of BZT-PT samples in perovskite phase and in the tetragonal system. The magnetic properties of these samples are studied by using SQUID. Intriguingly, exotic room temperature ferromagnetism has been observed in non-magnetic BZT-PT samples by vacuum annealing of the samples. In addition, a sub- stantial high dielectric constant has also been observed in vacuum annealed samples. The unprecedented magnetic and dielectric behavior has been attributed to the formation of oxygen vacancies which is explained by further studying the magnetic and dielectric behavior in air annealed samples. Furthermore, the dielectric re- laxation and frequency response of ac conductivity in BZT-PT samples found to follow universal dielectric re- laxation and Johnscher's power law response, respectively. A detailed density functional calculations show that the exotic magnetism BZT-PT is mainly due to the partial occupancy of t 2g and e g states of Ti ion by the delo- calized electrons generated due to oxygen vacancy. 1. Introduction In recent years, it has been a common trend to design new smart materials which will be smaller, faster and can execute multiple func- tionalities [1–3]. Magnetoelectrics is one of such class of smart mate- rials where ferroelectric and ferro/ferri/antiferromagnetic order para- meters are intimately coupled with each other so that ferroelectricity can be controlled by magnetic counterpart and vice-versa [4–6]. This unique feature has been exploited for variety of applications such as spintronic, memory devices, sensors etc. [7–10]. However, it is well- known that the ferroelectricity and ferromagnetism have contradictory origin, i.e., absence of d-electrons generate ferroelectricity whereas, the presence of d-electrons induces magnetism. Thus, it is highly challen- ging to combine these two ferroic-orders in single phase. So, for the realization of a good magnetoelectric material it is essential to have d 0 (proper) ferroelectricity and d 0 ferromagnetism to co-exist in a single phase. In fact, some reports reveal the possibility of d 0 ferromagnetism in non-magnetic materials, particularly in oxides such as ZnO, HfO 2 , SnO 2 etc, where d 0 ferromagnetism have been realized due to the in- troduction of holes in the valence band [11–13]. Further, the onset of d 0 ferromagnetism has been attributed to several factors such as: surface capping of molecules, under co-ordinated surface anions, anion va- cancies (example, oxygen vacancies) and anion vacancies carrying unpaired electrons [14–18]. Among (d 0 ) ferroelectric materials, highly tetragonal perovskite oxides such as; Bi(Zn 0.5 Ti 0.5 )O 3 (abbreviated as BZT) have garnered much attention not only due to their large spontaneous polarization and piezoelectric properties, but also for their wide range of technological applications including sensors, actuators and transducers [19–22]. The BZT exhibits a substantially high c/a ratio ~ 1.21 and high ionic po- larization, i.e., ~150 C cm -2 . Unfortunately, the perovskite phase of BZT is only stable at high pressure and under ambient conditions, it decomposes to undesirable non-perovskite phase [23]. In order to overcome this issue, Suchomel et al. have successfully prepared an alloy of BZT with PT (PbTiO 3 )[24], which is in perovskite phase under ambient condition. It is interesting to note that both BZT and PT are https://doi.org/10.1016/j.ceramint.2019.07.338 Received 28 May 2019; Received in revised form 28 July 2019; Accepted 29 July 2019 * Corresponding author. E-mail address: akhyaya@yahoo.com (A.K. Pattanaik). Ceramics International xxx (xxxx) xxx–xxx 0272-8842/ © 2019 Elsevier Ltd and Techna Group S.r.l. All rights reserved. Please cite this article as: Manasmita Mishra, et al., Ceramics International, https://doi.org/10.1016/j.ceramint.2019.07.338