Structural, thermal and electrical study of copper-doped strontium zirconate
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ORIGINAL PAPER
Structural, thermal and electrical study of copper-doped strontium zirconate Paramvir Kaur 1 & K. Singh 1 Received: 22 June 2019 / Revised: 5 July 2020 / Accepted: 23 August 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Copper-doped SrZrO3 perovskites prepared via solid-state reaction method are studied for structural, morphological, thermal and electrical properties using various characterisation techniques. The X-ray diffraction and Rietveld refinement confirm the monophasic orthorhombic structure of the undoped and doped samples. The shifting of the XRD peaks with doping is the manifestation of dopant Cu into the Zr site of SrZrO3 lattice. The thermal expansion curves of doped and undoped samples vary linearly with temperature. The conductivity of the samples increases with copper doping. The activation energy of the samples suggests mixed electronic and ionic (protonic) conduction in the present samples. The conductivity of the doped SrZrO3 increases up to three orders, i.e. 10−4 S cm−1 at 600 °C. The thermal and electrical properties are in the required SOFC range making Cudoped SrZrO3 suitable for use as cathode materials. Keywords Copper-doped strontium zirconate . Oxygen vacancy . Impedance spectroscopy . Dilatometry . Solid oxide fuel cell
Introduction Over the past few years, a lot of research is going on the development of materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs) [1–3]. One of the members of the A2+B4+O3-structured perovskite oxide family is SrZrO3. Owing to its high melting point (~ 2600 °C), chemical stability and fast ionic (protonic) conduction at high temperatures, SrZrO3 finds applications as cathode and electrolyte materials in IT-SOFCs [4–6]. Numerous researchers have been studying the evolution of different structural phase transitions of SrZrO3 [7, 8]. Basically, with the rise in the temperature, there is a decrement in the tilt angle of the ZrO6 octahedra which is responsible for the different phase transitions in SrZrO3. As the literature suggests, SrZrO3 has orthorhombic (Pbnm) structure at room temperature [9]. However, with the rise in temperature, SrZrO3 undergoes three phase transformations namely, orthorhombic (Pbnm) → orthorhombic (Cmcm) → tetragonal (I4/mcm) → cubic (Pm3m) at room temperature (RT), 700, 830 and 1170 °C, respectively [10].
* K. Singh [email protected] 1
School of Physics and Materials Science, Thapar Institute of Engineering and Technology, Patiala, Punjab 147004, India
These structural phase transitions have been studied using various techniques such as high-temperature X-ray diffraction and neutron powder diffraction [7, 8]. Thermal analytical techniques such as differential scanning calorimetry (DSC), differential thermal analysis (DTA) and dilatometry have also been used to study these high-temperature phase transitions [10–13]. Apart from the structural phase transitions, thermal expansion is also an important parameter. Zhao et al. observed how the phase transitions affect the bond
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