Author details

degree crystallinity and some trends of electrical properties due to the high surface reactivity of starting materials. It must be noted that this clear understanding

discussion presented, the evolution of a nanometer-to-micron grain size regime has been presented and the changing patterns of ferroelectrics are now clearly understood. It was found that the ferroelectric and magnetic properties generally correlated with intrinsic and extrinsic properties. The intrinsic contribution came from the contribution of the crystal structure in which orthorhombic, hexagonal, and more or less orthorhombic + hexagonal phases affected the phase that will contribute to the proper behavior of the ferroelectric. The effects of grain size of the two series of manganites have been observed by the scheme of nanosized starting particles followed by nano-to-micron grain sized regime data. Microstructural changes revealed a revolution of the crystal structure from orthorhombic to hexagonal at a larger grain size regime. The ferroelectric behavior was also observed to change with the change of microstructure along with the structural transformation from orthorhombic to hexagonal. For a general conclusion, the intrinsic effect occurred in the low sintering temperature region (600–1000°C for HoMnO3) and (600–900°C for YMnO3). The property changes at this region are due to crystal structure transformation. The extrinsic effect was more obvious at higher sintering temperature that is 1050–1250°C for HoMnO3 and 950–1250°C for YMnO3 in the hexagonal structure. The optimum condition to obtain a sample with very fine properties could be obtained by performing high-energy ball milling for 12 h followed by sintering at 1250°C with 10 h holding time. These steps were required in order to reach a very stable hexagonal structure for most advantageous ferroelectric and magnetic properties. The study of the evolution work has resulted in greater appreciation of the theoretical and experimental difficulties involved, if not in new knowledge of the behavior of multiferroic studies in evolution. In fact, there were no reported studies regarding these evolution works

The authors are thankful to the Materials Synthesis and Characterization Laboratory (MSCL), Functional Devices Laboratory (FDL), Institute of Advanced Technology (ITMA), and also the Department of Physics, Faculty of Science,

Universiti Putra Malaysia (UPM), for the measurement facilities.

has been made possible only through a progressive sintering scheme of nanometer-particle compacts from an unusually low sintering temperature (600°C) to a somewhat high sintering temperature (1250°C). From the

in the multiferroic field.

Functional Materials

Acknowledgements

110

Nor Hapishah Abdullah<sup>1</sup> , Raba'ah Syahidah Azis2,3\*, Muhammad Syazwan Mustaffa<sup>2</sup> , Mohd Nizar Hamidon<sup>1</sup> and Farah Nabilah Shafiee<sup>3</sup>

1 Functional Devices Laboratory (FDL), Institute of Advanced Technology, Universiti Putra Malaysia, UPM, Serdang, Selangor, Malaysia

2 Department of Physics, Faculty of Science, Universiti Putra Malaysia, UPM, Serdang, Selangor, Malaysia

3 Materials Synthesis and Characterization Laboratory (MSCL), Institute of Advanced Technology, Universiti Putra Malaysia, UPM, Serdang, Selangor, Malaysia

\*Address all correspondence to: rabaah@upm.edu.my

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
