CrFe_2O_4 - BiFeO_3 Perovskite Multiferroic Nanocomposites - A Review

摘要

Though semiconductor technology has advanced significantly in miniaturization and processor speed the "ideal" nonvolatile memory - memory that retains information even when the power goes is still elusive. There is a large demand for non-volatile memories with the popularity of portable electronic devices like cell phones and note books. Semiconductor memories like SRAMs and DRAMs are available but, such memories are volatile. After the advent of ferroelectricity many materials with crystal structures of Perovskite, pyrochlore and tungsten bronze have been derived and studied for the applications in memory devices. Ferroelectric Random Access Memories (FeRAM) are most promising. They are nonvolatile and have the greater radiation hardness and higher speed. These devices use the switchable spontaneous polarization arising suitable positional bi-stability of constituent ions and store the information in the form of charge. This paper is focused on the synthesis and characterizations of BiFeO_3 and xCrFe_2O_4-(1-x) BiFeO_3 nanoceramics which are most promising FeRAM materials. The effect of various-dopant-induced changes in structural, dielectric ac impedance, ferroelectric hysteresis, mechanism of the dielectric peak broadening and frequency dispersion have been addressed. It also deals with low temperature processing technique of those nanoceramics which has high dielectric and ferroelectric properties. These studies can be further extended to reinforce BiFeO_3 and CrFeO_4 materials with carbon nanotubes to obtain conductive composites using appropriate techniques.