The crystal structure of Sr2Nb2O7, a compound with perovskite-type slabs

Ishizawa, Nobuo; Μarumo, F.; Kawamura, Tsutomu; Kimura, Masakazu

doi:10.1107/s0567740875006462

Cited by 153 publications

(90 citation statements)

References 6 publications

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“…All atoms are on the mirror planes at x = 0 and 0.5. The perovskite-type slab contains TiO 6 octahedra and La (1) determined at room temperature (Ishizawa et al, 1975) after taking their origins at an appropriate position on the twofold screw axis. The thermal parameters for La2Ti20 7 at 1173 K are twice to three times larger than those for Sr2Nb207 at room temperature.…”

Section: Discussionmentioning

confidence: 99%

“…Since the Patterson maps calculated from the reflexion data were quite similar to those for Sr2Nb20 v (Ishizawa, Marumo, Kawamura & Kimura, 1975), the refinement of the structure was carried out with the full-matrix least-squares program LINUS (Coppens & Hamilton, 1970) using the positional parameters of Sr2Nb20 7 for the starting values. Anisotropic temperature factors were used for the metal atoms and isotropic ones for the O atoms.…”

Section: Methodsmentioning

confidence: 99%

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Compounds with perovskite-type slabs. V. A high-temperature modification of La2Ti2O7

Ishizawa¹,

Μarumo²,

Iwai³

et al. 1982

Acta Crystallogr B Struct Crystallogr Cryst Chem

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LazTi20 7 with the monoclinic space group P21 transforms its structure into one with the orthorhombic space group Cmc2~ at approximately 1053 K. The orthorhombic structure at 1173 + 10 K with a =-: 3.954 (2), b = 25.952 (8) and c = 5.607 (2) A and Z = 4 has been determined from three-dimensional X-ray diffraction data and refined to a conventional R value of 0.066 for 766 observed reflexions. The crystal is essentially isostructural with that of Sr2Nb20 7, in which * To whom correspondence should be addressed.0567-7408/82/020368-05501.00 all atoms are on the mirror plane at x = 0 or 0.5 and the corner-shared BO 6 octahedra and A atoms with twelve coordination form perovskite-type slabs. The structural change between the orthorhombic and monoclinic modifications is characterized by displacements of La atoms taking place within the respective planes perpendicular to the a axis on which the relevant La atoms lie, and by rotations of TiO 6 octahedra around axes parallel to the b axis and running through the respective Ti atoms. No significant displacement of the Ti positions occurs. Half of the mirror planes in the orthorhombic modification are lost on the phase transition and the remaining half survive as local mirror

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Compounds with perovskite-type slabs. V. A high-temperature modification of La2Ti2O7

Ishizawa¹,

Μarumo²,

Iwai³

et al. 1982

Acta Crystallogr B Struct Crystallogr Cryst Chem

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“…La2Ti207 belongs to a relatively small family of layered perovskite-related materials (Brandon & Megaw, 1970;Gasperin, 1975;Ishizawa, Marumo, Kawamura & Kimura, 1975). There are also a number of A2B207 alkali-metal niobates and tantalates adopting this structure type [for example, Ca2Nb207 (Brandon & Megaw, 1970) and Sr2Nb207 (Ishizawa et al, 1975)]; the optical and piezo-and ferroelectric properties of many of these phases are of interest (Nanamatsu, Kimura, Doi & Takahashi, 1971;Nanamatsu, Kimura & Kawamura, 1975).…”

Section: Introductionmentioning

confidence: 99%

The twin structure of La₂Ti₂O₇: X-ray and transmission electron microscopy studies

Schmalle¹,

Williams²,

Reller³

et al. 1993

Acta Crystallogr B Struct Sci

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LaaTi207, Mr = 485.613, monoclinic, P2~, a = 7.812(2), b= 5.5440 (7), c= 13.010 (2) A, /3 = 98.66 (1) °, V = 557.0 (4)/~3, Z = 4, T = 298 K, Dx = 5.790 Mg m -3, A(Mo Ka) = 0.71073 A, /z = 17.86 mm-1, F(000) = 856. The crystals are twinned. The twin I and twin II intensities are superimposed in reciprocal-lattice layers with h even. The a* and b* axes of the twin components run antiparallel. The angle between atwin* i and atwin* n is 17.12 °. The twinning operation has been identified to be a mirror plane perpendicular to the c* direction affecting only the oxygen positions in the structure: La and Ti atoms lie on an orthorhombic sublattice unchanged by the twinning. The structure refined on [FI 2 to R = 0.040, wR = 0.085 for 7972 observed reflections with I> 3tr(l). The refinement was carried out by * Author to whom all correspondence should be addressed. Present address: JASCO International Co. Ltd., 4-21 Sennin-cho 2-chome, Hachioji City, Tokyo 193, Japan.0108-7681/93/020235-10506.00 inclusion of the contributions from the two twin elements simultaneously, with the use of appropriate matrices to relate the atomic coordinates and reflection indices of each of the twin elements. The twin volume fraction was also refined and gave a = 0.1108 (3) as the volume fraction of twin I. The enantiomorphs in twin I and twin II have been shown to be opposite by refinement, on IF[, of the enantiopole, or Flack's x, parameter against reflection data that had been separated into separate sets for each twin element. Subsequently, several refinements, on IF1, of the twinned data set with the use of all possible combinations of enantiomorphs of each twin element yielded the best R/wR values (0.040 and 0.056) when the twin components contained opposite enantiomorphs. The general features of the structure determined by Gasperin [Acta Cryst. (1975), B31, 2129-2130] could be confirmed: the twins comprise distorted (4 + 1 + 1) TiO6 octahedra sharing vertices to form infinite perovskite-like layers three octahedra thick, bound by crystallographic © 1993 International Union of Crystallography 236 TWIN STRUCTURE OF La2Ti207 shears in the a direction. La atoms occupy distorted perovskitic A sites and interlayer sites. La2Ti207 is a member of an homologous series of An ÷ ,Bn ÷ 103n ÷ 5 (0 -< n --_ oo) compounds with n = 3. IntroductionLa2Ti207 belongs to a relatively small family of layered perovskite-related materials (Brandon & Megaw, 1970;Gasperin, 1975;Ishizawa, Marumo, Kawamura & Kimura, 1975). There are also a number of A2B207 alkali-metal niobates and tantalates adopting this structure type [for example, Ca2Nb207 (Brandon & Megaw, 1970) and Sr2Nb207 (Ishizawa et al., 1975)]; the optical and piezo-and ferroelectric properties of many of these phases are of interest (Nanamatsu, Kimura, Doi & Takahashi, 1971;Nanamatsu, Kimura & Kawamura, 1975). Gasperin, from her structure determination, indicated that La2Ti207 is a member of an homologous series of layered structures built from {110} perovskitic slabs differing in thick...

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“…In the paraelectric phase (above T c ), Cmcm space group has been proposed. In the ferroelectric phase, the space group changes to Cmc2 1 [2] and the spontaneous polarization appears along the orthorhombic c-axis. At room temperature, the spontaneous polarization P s Z9!10 K 2 C.m 2 is parallel to the c-axis and the coercive field is E c Z6!10 3 V. cm -1 .…”

Section: Introductionmentioning

confidence: 99%

“…Its single crystals have been studied extensively due to their remarkable piezoelectric properties [1][2][3]. It has low dielectric constant, coercive field and high heat resistance is expected because of its high melting point (w1700 8C).…”

Section: Introductionmentioning

confidence: 99%

Normal-incommensurate phase transition in (Sr_1−xBa_x)₂Nb₂O₇ferroelectric single crystals

Shabbir

Akishige

Kojima

2005

Science and Technology of Advanced Materials

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Micro-Brillouin and Raman light scattering experiments were performed on (Sr 1Kx Ba x ) 2 Nb 2 O 7 single crystals to investigate the effect of Ba addition on the normal-incommensurate phase transition. From the Brillouin frequency shift results, it was observed that the onset temperature of the normal-incommensurate phase decreased with increasing Ba concentration. This was associated to the suppression of the octahedra tilting due to substitution of larger ion on the A-site. The Raman intensity of the Q soft mode measured at room temperature also showed a similar behaviour with increasing x. q

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The crystal structure of Sr₂Nb₂O₇, a compound with perovskite-type slabs

Cited by 153 publications

References 6 publications

Compounds with perovskite-type slabs. V. A high-temperature modification of La2Ti2O7

Compounds with perovskite-type slabs. V. A high-temperature modification of La2Ti2O7

The twin structure of La₂Ti₂O₇: X-ray and transmission electron microscopy studies

Normal-incommensurate phase transition in (Sr_1−xBa_x)₂Nb₂O₇ferroelectric single crystals

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The crystal structure of Sr2Nb2O7, a compound with perovskite-type slabs

Cited by 153 publications

References 6 publications

Compounds with perovskite-type slabs. V. A high-temperature modification of La2Ti2O7

Compounds with perovskite-type slabs. V. A high-temperature modification of La2Ti2O7

The twin structure of La2Ti2O7: X-ray and transmission electron microscopy studies

Normal-incommensurate phase transition in (Sr1−xBax)2Nb2O7ferroelectric single crystals

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The crystal structure of Sr₂Nb₂O₇, a compound with perovskite-type slabs

The twin structure of La₂Ti₂O₇: X-ray and transmission electron microscopy studies

Normal-incommensurate phase transition in (Sr_1−xBa_x)₂Nb₂O₇ferroelectric single crystals