Structure characteristics and valence state study for La1−xNaxTiO3 synthesized under high-pressure and high-temperature conditions

Miao, Jipeng; Li, Guangshe; Liu, Hongjian; Xu, Duanfu; Lü, Zhe; Song, Yanbin; Su, Wenhui; Zheng, Ying

doi:10.1016/s0167-577x(99)00149-4

Cited by 28 publications

(5 citation statements)

References 11 publications

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“…All previous investigations of Na 0.5 La 0.5 TiO 3 have reported a disordered long‐range distribution of the A‐site cations (i.e., random distributions of Na + and La 3+ cations). The first such studies reported that the structure of Na 0.5 La 0.5 TiO 3 was cubic, space group

P m \bar{3} m

. Others later proposed an orthorhombic structure in space group Pnma .…”

Section: Introductionmentioning

confidence: 99%

Empirical Evidence for A‐Site Order in Perovskites

et al. 2016

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Models for composition–structure relationships are useful in both the lab and industry, yet few exist for perovskites-containing extrinsic defects or cation ordering. In this work, an empirical model is used to predict the existence of A-site cation ordering. Specifically, four compositions in the Na(1−3x)/2La(1+x)/2TiO3 system (x = 0.0, 0.0533, 0.1733 and 0.225) were synthesized using a conventional solid-state mixed-oxide method. The structure of the x=0 end-member (Na0.5La0.5TiO3) has been reported in various space groups, but always with a random distribution of Na+ and La3+ on the A site; however, empirical modeling suggests that it is not only ordered but also that a small volume increase accompanies the ordering process. While no evidence of long-range A-site ordering is observed in this composition via X-ray or neutron diffraction, electron-diffraction data indicate short-range ordering of Na+ and La3+ ions, with the degree of cation ordering decreasing (but the scale of ordered domains and degree of vacancy ordering generally increasing) with increasing x. First-principles calculations via density functional theory support both conclusions that short-range ordering in Na0.5La0.5TiO3 is stable and that it results in a volume increase with respect to the disordered analog. A similar analysis has been conducted for the Li(1−3x)/2La(1+x)/2TiO3 and Na(1−3x)/2La(1+x)/2(Mg0.5W0.5)O3 solid solutions. These systems provide additional validation of the accuracy and versatility of the empirical modeling method used

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P m \bar{3} m

. Others later proposed an orthorhombic structure in space group Pnma .…”

Section: Introductionmentioning

confidence: 99%

Empirical Evidence for A‐Site Order in Perovskites

et al. 2016

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“…The structure of Na 0.5 La 0.5 TiO 3 has been under controversy. The first few works reported a cubic structure for this compound [8][9][10]. Sun et al [6] reported rhombohedral structure in space group R 3c.…”

Section: Introductionmentioning

confidence: 99%

Structure and phase transition of Na_0.5La_0.5TiO₃

Garg¹,

Senyshyn²,

Boysen³

et al. 2008

J. Phys.: Condens. Matter

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A temperature dependent neutron powder diffraction study was carried out on Na 0.5 La 0.5 TiO 3 (NLT) from 298 K up to 1373 K. Rietveld analysis using high resolution x-ray and neutron powder diffraction data confirmed the rhombohedral structure (space group R 3c) of this compound. The rhombohedral phase transforms to cubic (Pm 3m) above 873 K. The temperature variation of the tilt angle, a continuous change of the specific volume across the transition, and the strain analysis suggest a second order nature of the cubic-rhombohedral phase transition, which is in conformity with the group theoretical prediction based on symmetry considerations.

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“…In this way, Δ r A can be used explicitly as a measure of A‐site ordering. Interestingly, while no evidence of long‐range A‐site ordering has been observed in the NLT system via x‐ray or neutron diffraction, this model clearly shows the pattern of errors leading to the conclusion of order. In fact, electron diffraction shows that the structure consists of nanodomains of order (short‐range order); thus, even short‐range order can be quantified with this model.…”

Section: Introductionmentioning

confidence: 69%

“…Initially, Na y La 1− y TiO 3 ( y = 0.05‐0.8) perovskites were observed to exhibit cubic symmetry with unit‐cell volumes increasing with y for 0.05 ≤ y < 0.1 then decreasing for y ≥ 0.1. It should be noted that this stoichiometry is problematic, as a fully occupied A site requires that the upper limit on y be 0.5.…”

Section: Introductionmentioning

confidence: 99%

Empirical models for layered A‐site ordering in perovskite titanates

Smith

Ubic

2018

J Am Ceram Soc

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In industry and labs, predictive models describing processing-structure relationships are inherently valuable, yet few exist for cation ordering in perovskites. In this work, 15 compositions in the [(Na y Li 1−y ) (1−3x)/2 La (1+x)/2 ]TiO 3 (NLLT) system (y = 0.25, 0.5, and 0.75; x = 0, 0.0533, 0.1, 0.1733, and 0.225) were synthesized using a conventional solid-state mixed-oxide method. X-ray diffraction data show that some degree of long-range ordering of A-site cations exists for x ≥ 0.1, although electron-diffraction data indicate that short-range ordering exists even for x < 0.1, with the degree of ordering decreasing as the value of x increases. Empirical models have been derived for the A-site ordering parameter (η) as well as the resultant expansion (Δr A ) for each y series in the NLLT system, from which two general models were derived for perovskites with any arbitrary degree of 1:1 layered A-site ordering. These general models allow for the prediction of the order parameter and resulting expansion using only published ionic radii data.

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Structure characteristics and valence state study for La1−xNaxTiO3 synthesized under high-pressure and high-temperature conditions

Cited by 28 publications

References 11 publications

Empirical Evidence for A‐Site Order in Perovskites

Empirical Evidence for A‐Site Order in Perovskites

Structure and phase transition of Na_0.5La_0.5TiO₃

Empirical models for layered A‐site ordering in perovskite titanates

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Structure characteristics and valence state study for La1−xNaxTiO3 synthesized under high-pressure and high-temperature conditions

Cited by 28 publications

References 11 publications

Empirical Evidence for A‐Site Order in Perovskites

Empirical Evidence for A‐Site Order in Perovskites

Structure and phase transition of Na0.5La0.5TiO3

Empirical models for layered A‐site ordering in perovskite titanates

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Product

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Structure and phase transition of Na_0.5La_0.5TiO₃