Structures of NaTaO<sub>3</sub> by neutron powder diffraction

Ahtee, Maija; Darlington, C. N. W.

doi:10.1107/s0567740880005183

Cited by 70 publications

(47 citation statements)

References 11 publications

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“…However this contradiction does not indicate that the supposed three phase transitions do not exist. The similar phenomena have been reported in some previous work [6,7,9,[13][14][15]. It has been confirmed that NaTaO 3 experiences a series of phase transitions: orthorhombic (in rhombic orientation)/orthorhombic(in pseudocubic orientation)/tetragonal/cubic [6,7,13].…”

Section: Resultssupporting

confidence: 84%

“…On the other hand, the similar perovskite compound NaTaO 3 also has several phase transitions at 475, 580 and 650 • C [6,7]. Though the earlier work reported NaTaO 3 as a ferroelectric with Curie temperature about 475 • C, the later detailed dielectric investigations by Iwasaki and Ikeda stated that there was no electric hysteresis loop or any anomaly in the ε(T ) curve observed either for the ceramic samples or single crystals [8].…”

Section: Introductionmentioning

confidence: 91%

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Dielectric and Ferroelectric Characterization of Na(Ta,Nb)O3 Solid Solution Ceramics

et al. 2005

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Ceramics in the Na(Ta 1−x Nb x )O 3 system were prepared by a solid state reaction approach, and their dielectric characteristics were evaluated together with the structures. The complete solid solution with orthorhombic structures was observed in the present system, and three supposed phase transitions at about 475, 580 and 650 • C were observed by DTA. Only one dielectric anomaly was observed at high temperature for x = 0.2 and 0.4, and alternative dielectric anomaly (a diffused dielectric peak) was observed around 170 and 380 • C for x = 0.6 and 0.8, respectively. The compositions of 0.6 and 0.8 are weakly ferroelectric and those of 0.2 and 0.4 are supposed to be antiferroelectric at room temperature.

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Section: Resultssupporting

confidence: 84%

Section: Introductionmentioning

confidence: 91%

Dielectric and Ferroelectric Characterization of Na(Ta,Nb)O3 Solid Solution Ceramics

et al. 2005

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“…at 1033 K (Ahtee et al 1978), NaTaO3 at 803 K (Ahtee and Darlington 1980), and CsSrC13 at 363 K (Midorikawa et al 1976). …”

Section: Tentative Determination Of Space Groupmentioning

confidence: 98%

“…Note the appearance of a weak reflection at about 57.7 ~ in Cmcm at 673 K, which did not occur in Pbnm at 295 K. The appearance of such superlattice reflections was also observed in perovskites such as SrZrO3 (Ahtee etal. 1978) and NaTaO3 (Ahtee and Darlington 1980). Of course, transformation to a tetragonal phase (I4/mcm or P4/mbm) is always possible after it has transformed to Cmcm (Aleksandrov 1976 Step-scan powder diffraction patterns at 295 K (top) and 673 K (bottom) for the region of 55 ~ to 59 ~ The indicated reflection indices are calculated according to Pbnm (top) and Crncm (bottom).…”

Section: Tentative Determination Of Space Groupmentioning

confidence: 99%

Phase transition in CaGeO3 perovskite: Evidence from X-ray powder diffraction, thermal expansion and heat capacity

et al. 1991

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Abstract. High-temperature x-ray powder diffraction study by the full pattern Rietveld method of orthorhombic CaGeO3 (Pbnm at ambient condition) perovskite confirms the previously observed phase transition at Tc = 520 K. The measured volumetric thermal expansion coefficients are 3.1 x 10 -s (K -1) below Tc and 3.5x 10 .5 (K -1) above Tc. The space group at T>Tc has been tentatively identified as Cmcm. Such a transition involves the disappearance of one of the two octahedral rotations in the (001) plane, and the doubling of the unit cell volume, with c axis unchanged. Although this transition should be of first order from symmetry considerations, the distortion of the Pbnm phase decreases continuously as the temperate approaches Tc and there is no observable volume discontinuity at Tc. The measured heat capacity places an upper limit on the enthalpy of transition of 50 J/mol, which is quite reasonable in terms of the crystallographic nature of this phase transition.

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“…No known examples SrZrO 3 (973-1103 K) NaNbO 3 (793-848 K) NaTaO 3 (803-873 K) NHaMnCI 3 (128 K) PrAIO 3 ( < 135 K) Marezio, Dernier, Chenevas & Joubert (1973) Chenevas, Joubert, Marezio & Bochu (1975 Ahtee, Glazer & Megaw (1972) Ahtee & Darlington (1980) Tornero, Cano, Fayos & Martinez-Ripoll (1978) Burbank (1970) …”

mentioning

confidence: 99%

Octahedral Tilting in Perovskites. II. Structure Stabilizing Forces

Woodward¹

1997

Acta Crystallogr B Struct Sci

629

480

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The 23 Glazer tilt systems describing octahedral tilting in perovskites have been investigated. The various tilt systems have been compared in terms of their A-cation coordination and it is shown that those tilt systems in which all the A-cation sites remain crystallographically equivalent are strongly favored, when all the A sites are occupied by the same ion. Calculations based on both ionic and covalent models have been performed to compare the seven equivalent A-site tilt systems. Both methods predict that when the tilt angles become large, the orthorhombic a+b-b -tilt system will result in the lowest energy structure. This tilt system gives the lowest energy structure because it maximizes the number of short A---O interactions. The rhombohedral a-a-a-tilt system gives a structure with a slightly lower Madelung energy, but increased ion-ion repulsions destabilize this structure as the tilt angles increase. Consequently, it is stabilized by highly charged A cations and small to moderate tilt angles. The ideal cubic a°a°a° tilt system is only observed when stabilized by oversized A cations and/or M---O 7r-bonding. Tilt systems with nonequivalent A-site environments are observed when at least two A cations with different sizes and/or bonding preferences are present. In these compounds the ratio of large-to-small cations dictates the most stable tilt system.

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Structures of NaTaO₃ by neutron powder diffraction

Cited by 70 publications

References 11 publications

Dielectric and Ferroelectric Characterization of Na(Ta,Nb)O3 Solid Solution Ceramics

Dielectric and Ferroelectric Characterization of Na(Ta,Nb)O3 Solid Solution Ceramics

Phase transition in CaGeO3 perovskite: Evidence from X-ray powder diffraction, thermal expansion and heat capacity

Octahedral Tilting in Perovskites. II. Structure Stabilizing Forces

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Structures of NaTaO3 by neutron powder diffraction

Cited by 70 publications

References 11 publications

Dielectric and Ferroelectric Characterization of Na(Ta,Nb)O3 Solid Solution Ceramics

Dielectric and Ferroelectric Characterization of Na(Ta,Nb)O3 Solid Solution Ceramics

Phase transition in CaGeO3 perovskite: Evidence from X-ray powder diffraction, thermal expansion and heat capacity

Octahedral Tilting in Perovskites. II. Structure Stabilizing Forces

Contact Info

Product

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Structures of NaTaO₃ by neutron powder diffraction