TY - JOUR
T1 - Anomalous broad dielectric relaxation in Bi1.5Zn1.0Nb1.5O7 pyrochlore
AU - Kamba, Stanislav
AU - Porokhonskyy, Viktor
AU - Pashkin, Alexej
AU - Bovtun, Viktor
AU - Petzelt, Jan
AU - Nino, Juan C.
AU - Trolier-McKinstry, Susan
AU - Lanagan, Michael T.
AU - Randall, Clive A.
PY - 2002/8/1
Y1 - 2002/8/1
N2 - The complex dielectric response of Bi1.5Zn1.0Nb1.5O7 cubic pyrochlore ceramics was investigated between 100 Hz and 100 THz by a combination of low-frequency capacitance bridges, a high-frequency coaxial technique, time domain transmission THz spectroscopy, and infrared spectroscopy. The data obtained between 10 K and 400 K revealed glasslike dielectric behavior: dielectric relaxation is observed over a wide frequency and temperature range, and the dielectric permittivity and loss maxima shift to higher temperature values by almost 200 K with increasing measuring frequency. The distribution of relaxation frequencies broadens on cooling and can be described by a uniform distribution. The high-frequency end of the distribution at ∼1011 Hz is almost temperature independent and its low-frequency end obeys the Arrhenius Law with an activation energy of ∼0.2 eV. The relaxation is assigned to the local hopping of atoms in the A and O' positions of the pyrochlore structure among several local potential minima. The barrier height for hopping is distributed between 0 and 0.2 eV. Such an anomalously broad distribution may have its origin in the inhomogeneous distribution of Zn2+ atoms and vacancies on Bi3+ sites, which gives rise to random fields and nonperiodic interatomic potential. Frequency independent dielectric losses (1/f noise) are observed at low temperatures, which seems to be a universal behavior of disordered systems at low temperatures.
AB - The complex dielectric response of Bi1.5Zn1.0Nb1.5O7 cubic pyrochlore ceramics was investigated between 100 Hz and 100 THz by a combination of low-frequency capacitance bridges, a high-frequency coaxial technique, time domain transmission THz spectroscopy, and infrared spectroscopy. The data obtained between 10 K and 400 K revealed glasslike dielectric behavior: dielectric relaxation is observed over a wide frequency and temperature range, and the dielectric permittivity and loss maxima shift to higher temperature values by almost 200 K with increasing measuring frequency. The distribution of relaxation frequencies broadens on cooling and can be described by a uniform distribution. The high-frequency end of the distribution at ∼1011 Hz is almost temperature independent and its low-frequency end obeys the Arrhenius Law with an activation energy of ∼0.2 eV. The relaxation is assigned to the local hopping of atoms in the A and O' positions of the pyrochlore structure among several local potential minima. The barrier height for hopping is distributed between 0 and 0.2 eV. Such an anomalously broad distribution may have its origin in the inhomogeneous distribution of Zn2+ atoms and vacancies on Bi3+ sites, which gives rise to random fields and nonperiodic interatomic potential. Frequency independent dielectric losses (1/f noise) are observed at low temperatures, which seems to be a universal behavior of disordered systems at low temperatures.
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U2 - 10.1103/PhysRevB.66.054106
DO - 10.1103/PhysRevB.66.054106
M3 - Article
AN - SCOPUS:0036695289
SN - 0163-1829
VL - 66
SP - 541061
EP - 541068
JO - Physical Review B - Condensed Matter and Materials Physics
JF - Physical Review B - Condensed Matter and Materials Physics
IS - 5
M1 - 054106
ER -