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1

Digitale Medien

Dielectric and electric properties of donor- and acceptor-doped ferroelectric SrBi2Ta2O9 (2001)

Kumar, M. Mahesh ; Ye, Z.-G.

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 90 (2001), S. 934-941

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Substitutions by aliovalent cations on the Sr2+ and Bi3+ sites of ferroelectric SrBi2Ta2O9 (SBT) have been carried out, which result in modified dielectric and electrical properties of SBT. The substitution of 10 mole % Fe3+ for Sr2+ shows an increase of 80 °C in TC, whereas Ca2+ substitution for Bi3+ gives rise to diffused and frequency dispersive dielectric maxima with a relaxor-like behavior. The presence of Ca2+ in the (Bi2O2)2+ layers appears to enhance the mobility of charge carriers thus increasing the bulk conduction of the sample. On the other hand, Fe3+ addition in the perovskite-like units results in a sharp dielectric anomaly at the ferroelectric phase transition, with a bulk conductance similar to that of pure SBT compound, but with a reduced space charge relaxation time. The low temperature conductivity mechanism shows a frequency dependence, which can be ascribed to the space charge mainly due to the oxygen vacancies. The dielectric and conductivity properties of the Ca2+-doped SBT make it a promising material for the fatigue resistance in device applications. © 2001 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.1383267

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2

Digitale Medien

Dielectric relaxation in Ba0.96Bi0.04Ti0.96Fe0.04O3 (1998)

Kumar, M. Mahesh ; Suresh, M. B. ; Suryanarayana, S. V. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 84 (1998), S. 6811-6814

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Samples of Ba0.96Bi0.04Ti0.96Fe0.04O3 were prepared by a solid state reaction method. Data on the dielectric constant as a function of temperature and frequency were obtained in the temperature range 35–180 °C at 10 and 100 kHz. The material shows a diffuse phase transition. With increasing frequency, the transition temperature shifts towards lower temperature, resembling that of a relaxor ferroelectric with a negative shift in Tc. Impedance analysis confirms the relaxor behavior. © 1998 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.368875

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3

Digitale Medien

Structure property relations in BiFeO3/BaTiO3 solid solutions (2000)

Kumar, M. Mahesh ; Srinivas, A. ; Suryanarayana, S. V.

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 87 (2000), S. 855-862

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: BiFeO3, when forming a solid solution with BaTiO3, shows structural transformations over the entire compositional range. Above 70 mole % of BiFeO3 the structure is rhombohedral and below 4 mole %, it is tetragonal. In between the structure is cubic. The ferroelectric TC decreases with increasing composition of BaTiO3 and a relatively small relaxation is observed. Impedance measurements showed a structural dependence and analysis of which has clearly shown that the capacitance observed is from the bulk of the sample. Relaxation time (τ) of BiFeO3 was estimated using the relaxation times of the intermediate compositions. Magnetization measurements showed field induced ferromagnetism. As the structure becomes cubic with increasing concentration of BaTiO3, paramagnetism sets in, as evidenced by the electron spin resonance spectra. © 2000 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.371953

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4

Digitale Medien

Ferroelectricity in a pure BiFeO3 ceramic (2000)

Kumar, M. Mahesh ; Palkar, V. R.

Woodbury, NY : American Institute of Physics (AIP)

Applied Physics Letters 76 (2000), S. 2764-2766

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ISSN: 1077-3118

Quelle: AIP Digital Archive

Thema: Physik

Notizen: The difficulties in synthesizing phase pure BiFeO3 are well known. In this letter we are reporting the optimized synthesis conditions for obtaining phase pure BiFeO3 ceramic. The oxide mixing technique followed by leaching with dilute nitric acid has been used for the synthesis. X-ray diffraction pattern indicated that the sample is phase pure. Scanning electron microscopy along with energy dispersive x-ray fluorescence analysis confirmed the chemical homogeneity of the sample. No segregation of the impurity phase in the matrix was detected. Moreover, Bi/Fe atomic ratio is observed to be ∼1. The ferroelectric transition of the sample at 836 °C has been detected by differential thermal analysis. © 2000 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.126468

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