Ferroelectric behavior in nanocrystalline KNbO₃ synthesized by a modified polymerized complex method

Abstract

Effect of nanocrystalline size of the particles on ferroelectric properties of KNbO₃ is studied. Properties like hysteresis parameters, phase transition temperatures and domain morphology in nanocrystallites were studied by using P-E hysteresis, differential scanning calorimetry (DSC) and transmission electron microscopy (TEM) techniques, respectively. Nanocrystalline KNbO₃ compound was synthesized by a modified polymerized complex method and room-temperature structural phase was characterized by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. Field emission gun-scanning electron microscopy (FEG-SEM) was used to reveal the size and morphology of the particles. It was found that the present nanoparticles of sizes ranging from 50 to 250 nm bears polarization values <1 μC/cm², and undergo cubic-tetragonal and tetragonal-orthorhombic phase transitions at 312 and 87 °C respectively. Although the value of polarization is small as compared to the bulk reported in the literature, the nature of P-E loops along with phase transitions and presence of 60, 90 and 180° domain structures indicates retention of ferroelectric nature in KNbO₃ even at the nanolevel.

Keywords:

• Nanocrystalline material
• ferroelectrics
• domain structure
• phase transition

Acknowledgment

The authors thank to STIC (Kochi, India), SAIF-NEHU (Shillong, India) and IIT Bombay (India) for XRD, TEM and FEG-SEM facilities, respectively.