Minor Dielectric Anomalies in ANbO<sub>3</sub>(A-Li, Na, K) Single Crystals in the 100–300°C Temperature Range

Raevskaya, S. I.; Reznitchenko, L. A.; Semenchev, A. F.; Lisitsina, S. O.; Smotrakov, V. G.; Eremkin, V. V.; Dul’kin, E.

doi:10.1080/00150190490493195

Cited by 1 publication

(2 citation statements)

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“…This type of anomaly was previously reported at 423 K for undoped NNO and shifts towards higher temper atures (∼453 K) when Li or K is substituted at Na sites of the perovskite lattice [23]. On the basis of detailed temperature-dependent structural, optical and dielectric studies, Raevskii et al concluded that such an additional phase transition can be close to a second-order transition taking place between two orthorhombic AFE rhombohedral phases (between 423 K and 453 K) [23][24][25].…”

Section: Resultssupporting

confidence: 63%

“…This temper ature dependence of DSC data collected under a heating cycle in the presence of an Ar gas ambient shows two weak anomalies: the first is in the temperature range 770-819 K and is associated with T AFE and the second anomalous change in heat flow takes place between 594 K and 668 K, which is close to the structural phase transition T P-R (643 K) observed in the dielectric data. Moreover, a giant cusp was evident in the DSC data at 429 K which is linked to the second-order incommensurate phase transition T p 1 noticed in ε r (T) [24][25][26]. These studies reveal that any change in the ε r (T) is accompanied by a definite change in the thermodynamic order parameter of the investigated system.…”

Section: Resultsmentioning

confidence: 57%

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Thermal hysteresis and vibrational excitations in NiO containing NaNbO₃

George

Dar

Joshi

et al. 2019

J. Phys. D: Appl. Phys.

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A systematic study of the dielectric hysteresis and temperature-dependent vibrational excitations of NiO containing antiferroelectric (AFE) NaNbO 3 composites is reported. The Mott insulator NiO plays a significant role in the crystal structure of NaNbO 3 . In particular, for low and moderate substitutions of NiO, a transition from orthorhombic to monoclinic symmetry is evident at room temperature. The temperature dependence of the relative dielectric permittivity, ε r (T), exhibits an anomalous change in its magnitude across three distinct phase transitions of NaNbO 3 at 449 K, 665 K and 751 K. These are, respectively, associated with a second-order phase transition occurring due to incommensurate phase between two orthorhombic AFE orderings, change from the orthorhombic P-to R-phase (T P-R ) without altering the AFE structure and an orthorhombic R-to S-phase transition accompanied by an AFE to paraelectric transition. A large thermal hysteresis (∆T hys ∼ 38 K) was evident in ε r and ac resistivity (ρ ac ) between the temperatures 473 K and 673 K signifying the firstorder nature of the T P-R transition. At room temperature, for higher NiO content, a new mode centred at 838 cm −1 was observed in the Raman spectra along with a two-magnon mode at 1496 cm −1 , a broad longitudinal optical mode (2LO) at 1096 cm −1 and a weak translational optical mode (2TO) at 726 cm −1 . At low temperatures, down to 80 K, several peculiar features are evident in the Raman spectra of NbO 6 octahedra which are associated with the structural and antiferromagnetic transition of NaNbO 3 and NiO, respectively.

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