Abstract
Three complex polycrystalline samples of Bi1-xPbxFe1-x Zrx-yTiyO3,with the combination of (i) x, y = 0.0 (BFO), (ii) x = 0.5 and y = 0.5 (BFPTO)and (iii) x = 0.5 and y = 0.25 (BFPZTO) were prepared by a standard mixed oxide (solid state reaction route) method at optimized calcinations (900oC) and sintering (930-950oC)temperatures. The effect of multiple (Pb, Ti and/or Zr) substitutions of different amount onthe permittivity, impedance and modulus characteristics of the materials has been investigated at different frequencies and temperature.Limitation associated with BiFeO3 (BFO) due to its semiconducting behavior acts as constraint in polling the material at room temperature leading to large dielectric loss. Attempts were made to minimizethe loss by substitution of Pb on the Bi site and Ti and/or Zr at the Fe site of BFO. The study indicates that the phase transition temperature of BFO is lowered,the degree of diffuse phase transition is enhanced and electrical parameters (dielectric constant, electrical resistivity, remnant polarization and maximum polarization) areincreased with a significant reduction in dielectric loss as a consequence of the substitution. Detailed studies of Nyquist plots with impedance and electric modulus data suggest that the existence of non-Debye type of relaxation phenomena in the materials. The ac conductivity study reveals that the conduction mechanism in the material obeys universal Jonscher’s power law.
Highlights
Though a large number of ferroelectric oxides are available, some perovskite oxides of a general formula,ABO3(a=mono-divalent and B=tri-hexavalent ions) such as BaTiO3, PbTiO3, Pb(ZrTi)O3 (PZT)etc. exhibit high dielectric constant(permittivity), spontaneous polarization, piezoelectric coefficient, pyroelectric current, transition temperature above room temperature, etcwhich enhance their potentiality for technological applications
These unique properties are resulted from their crystal structures that affectthe domain wall formation and orientation under external stimulation.Attempts have been made to develop new materials with unique and improved properties by substitutingsuitable element(s) at the A or/ B site (s) or combining different perovskites in suitable proportions[14].Among the perovskites, BiFeO3 (BFO) is considered as a unique material which goes to various structural phase transitions [5]
Both PbTiO3 and PZT are associated with lead 4810 | P a g e April2017 www.cirworld.com vacancies due to evaporation of Pb during the processing, which leads to the increase in acceptor levels in the crystal, the conductivity problem and dielectric loss of BFO can be reduced significantly by substituting different elements (Pb, Ti, Zr) of PZT into A/B-sites of BFO in suitable proportions[10,11,12,13]
Summary
Though a large number of ferroelectric oxides are available, some perovskite oxides of a general formula,ABO3(a=mono-divalent and B=tri-hexavalent ions) such as BaTiO3, PbTiO3, Pb(ZrTi)O3 (PZT)etc. exhibit high dielectric constant(permittivity), spontaneous polarization, piezoelectric coefficient, pyroelectric current, transition temperature above room temperature, etcwhich enhance their potentiality for technological applications. Exhibit high dielectric constant(permittivity), spontaneous polarization, piezoelectric coefficient, pyroelectric current, transition temperature above room temperature, etcwhich enhance their potentiality for technological applications These unique properties are resulted from their crystal structures that affectthe domain wall formation and orientation under external stimulation.Attempts have been made to develop new materials with unique and improved properties by substitutingsuitable element(s) at the A or/ B site (s) or combining different perovskites in suitable proportions[14].Among the perovskites, BiFeO3 (BFO) is considered as a unique material which goes to various structural phase transitions [5]. The effect of multiple substitution on the structural, dielectric and electrical properties of the material (BFO) at high temperatures in a wide frequency range (1kHz – 1MHz) is reported here
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