BNT-BT as the future lead-free functional material for PTCR, actuator and sensor applications

• Applicant: Dr.-Ing. Jan Manuel Hinterstein
• Subject Area: Synthesis and Properties of Functional Materials
• Term: from 2015 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 276699501

• Final Report Year: 2023

Final Report Abstract

Living in a changing environment has led to a revised ecological awareness all over the world and improving energy efficiency is one of the most important tasks for the future in Materials Science. Consequently, governmental legislations all over the world have driven the search for sustainable lead-free functional materials, which has become one of the most challenging topics in engineering science. Amongst the promising systems, barium titanate (BT) and bismuth sodium titanate (BNT) attracted wide interest in the scientific community as possible alternatives and exhibited significantly improved properties through doping. These functional electroceramics involve the application of voltages, electric fields or mechanical loads. Therefore, a carefully adjusted resistivity and low porosity are mandatory material constraints. For the material development and characterisation within this Emmy Noether project, four PhD students carried out individual subprojects. I. The function of electroceramics highly depends on electrical and dielectric properties. Additionally, the microstructure plays a crucial role. To adjust these properties and control a dense microstructure with defined grain sizes, a careful investigation of the defect chemistry is mandatory. This project focussed on understanding the effects of non-stoichiometry in BNT, BT as well as their solid solution and the effects of doping on the material properties and sintering behaviour. II. Sensor and actuator materials rely on the conversion of an electric field in macroscopic strain or vice versa. With a new method, developed in my group, all strain mechanisms in these materials can be quantified within a single experiment based on information on the atomic scale. With this technique, the macroscopic response to an external stimulus can be calculated from diffraction experiments. Project II, therefore, investigated the strain mechanisms on the newly developed materials from I, III and IV. III. In order to develop lead-free positive temperature coefficient (PTC) materials, the Curie temperature (Tc) has to be increased. For BT-based materials this can be achieved by the addition of BNT. In addition to controlling the defect chemistry and sintering behaviour of BNT in combination with BT, this project focused on the development of lead-free PTC ceramics. IV. All projects within the Emmy Noether group are based on BT. Since BT is a model system for ferroelectricity, a deep insight into the fundamental properties is mandatory. The functional properties of BT are dependent on the grain size and therefore this project focused on the grain size dependent electromechanical and dielectric properties of BT.

Publications

• Powder diffraction in external electric and magnetic fields. International Tables for Crystallography, 174-188.
  Ehrenberg, H.; Hinterstein, M.; Senyshyn, A. & Fuess, H.
  
• Influence of microstructure on symmetry determination of piezoceramics. Journal of Applied Crystallography, 51(3), 670-678.
  Hinterstein, M.; Mgbemere, H. E.; Hoelzel, M.; Rheinheimer, W.; Adabifiroozjaei, E.; Koshy, P.; Sorrell, C. C. & Hoffman, M.
  
• Determining fundamental properties from diffraction: Electric field induced strain and piezoelectric coefficient. Physical Review B, 99(17).
  Hinterstein, M.; Lee, K.-Y.; Esslinger, S.; Glaum, J.; Studer, A. J.; Hoffman, M. & Hoffmann, M. J.
  
• Revealing the role of local stress on the depolarization of BNT-BT-based relaxors. Physical Review Materials, 3(5).
  Glaum, Julia; Heo, Yooun; Acosta, Matias; Sharma, Pankaj; Seidel, Jan & Hinterstein, Manuel
  
• The complex structural mechanisms behind strain curves in bismuth sodium titanate–barium titanate. Applied Physics Letters, 116(18).
  Lee, Kai-Yang; Shi, Xi; Kumar, Nitish; Hoffman, Mark; Etter, Martin; Winter, Jens; Lemos, da Silva Lucas; Seifert, Daniela & Hinterstein, Manuel
  
• Size Effect on Ferroelectricity in Nanoscaled BaTiO3. Engineering Materials, 123-133.
  da Silva, Lucas Lemos & Hinterstein, Manuel
  
• Uncovering the symmetry of the induced ferroelectric phase transformation in polycrystalline barium titanate. Journal of Applied Physics, 130(23).
  Lemos, da Silva Lucas; Lee, Kai-Yang; Petrick, Simon; Etter, Martin; Schökel, Alexander; Chaves, Cesar Giovanni; Oliveira, da Silva Nilson; Lalitha, K. V.; Picht, Gunnar; Hoffmann, Michael J. & Hinterstein, Manuel
  
• Deciphering the phase transition-induced ultrahigh piezoresponse in (K,Na)NbO3-based piezoceramics. Nature Communications, 13(1).
  Zhang, Mao-Hua; Shen, Chen; Zhao, Changhao; Dai, Mian; Yao, Fang-Zhou; Wu, Bo; Ma, Jian; Nan, Hu; Wang, Dawei; Yuan, Qibin; da Silva, Lucas Lemos; Fulanović, Lovro; Schökel, Alexander; Liu, Peitao; Zhang, Hongbin; Li, Jing-Feng; Zhang, Nan; Wang, Ke; Rödel, Jürgen & Hinterstein, Manuel
  
• Multigrain phase-field simulation in ferroelectrics with phase coexistences: An improved phase-field model. Computational Materials Science, 203, 111056.
  Fan, Ling; Werner, Walter; Subotić, Swen; Schneider, Daniel; Hinterstein, Manuel & Nestler, Britta
  
• In situ neutron diffraction for analysing complex coarse-grained functional materials. Journal of Applied Crystallography, 56(4), 1242-1251.
  Hinterstein, Manuel; Lemos, da Silva Lucas; Knapp, Michael; Schoekel, Alexander; Etter, Martin & Studer, Andrew