Tetramethylammonium-calcium-triazid. Darstellung und Kristallstruktur

Mautner, Franz A.; Krischner, H.; Kratky, Christoph

doi:10.1007/bf00808305

Cited by 23 publications

(16 citation statements)

References 3 publications

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“…13,33,44 Shifts may also act as the sole order parameter, as in [NĲCH 3 ) 4 ]CaĲN 3 ) 3 , where the checkerboard shift polarised along a single axis is sufficient to account for the P4/nmm symmetry. 12,26 Azides are the only family where the shear shift (Γ 5 + ) acts as a primary order parameter. This is particularly obvious in the high-temperature phase of [(CH 3 ) 3 NH]MnĲN 3 ) 3 , where this mode is the only active framework distortion, leading to R3m symmetry.…”

Section: Resultsmentioning

confidence: 99%

Tilts and shifts in molecular perovskites

Boström

2020

CrystEngComm

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Section: Resultsmentioning

confidence: 99%

Tilts and shifts in molecular perovskites

Boström

2020

CrystEngComm

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“…The first successful example of a biorganic HP was reported a few years after the first HP(X) structures, [174] employing tetraethylammonium on the A-site and an azide anion on the X-site, forming an HP(AX) structure. This may be attributed to the fact that research on such structures is yet scarce and a link toward the term HPs is rather new and came not before the recent prominence of this materials class with respect to PV applications.…”

Section: Perovskites With More Than One Organic Ionmentioning

confidence: 99%

“…However, with the notation we propose, we can unambiguously refer to them by the sites referring to organic ions given in brackets HP(AX). The first successful example of a biorganic HP was reported a few years after the first HP(X) structures, [174] employing tetraethylammonium on the A-site and an azide anion on the X-site, forming an HP(AX) structure. Due to size considerations, HP(BX) is unlikely and the only other possible variant appears to be HP(AB) structures.…”

Section: Perovskites With More Than One Organic Ionmentioning

confidence: 99%

Mix and Match: Organic and Inorganic Ions in the Perovskite Lattice

Gebhardt

Rappe

2018

Advanced Materials

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X-site anions are possible, with only two general requirements that must be fulfilled: i) charge neutrality in the ABX 3 unit (typically, X is a divalent or monovalent anion, hence A and B cations with oxidation states between +1 and +5 can be combined) and ii) the ionic radii of the chosen composition must allow the above coordination, or different phases become more stable. Both of these simple design rules have a certain flexibility.The electronic argument i) can be stretched by allowing the combination of multiple ABX 3 units to form an overall charge neutral unit. For example, this is the case when considering A 2 BB′X 6 or AA′B 2 X 6 systems. Such double perovskite systems are known with B and B′ (A and A′) being the same elemental species (disproportion in oxidation state, e.g., Cs 2 Au + Au 3+ I 6 ) [20] or different ones (e.g., SrBaTi 2 O 6 [21] and SrPbTi 2 O 6 [22] for A-site disproportion or K 2 NbTaO 6 [23] and Bi 2 FeCrO 6 [24] for the B-site). Of course, this concept can also be used to combine three ABX 3 units (e.g., (CaTiO 3 ) n (SrTiO 3 ) l (BaTiO 3 ) m [25-27]) and much more complex stoichiometries with mixed ratios (e.g., (Pb 2 InNbO 6 ) 3/4 (Ba 2 InBiO 6 ) 1/4 [28] or [CaMn 3 3+ ][Mn 3 3+ Mn 4+ ] O 12 ] [29] ). Furthermore, although the bonding character in oxide perovskites is often mainly ionic, some compositions have an increased level of covalency (e.g., halides, sulfides, Bi-and Pbbased oxide perovskites). Thus, the electronic shell configuration and other effects like the steric demands of a metal lonepair will influence the structure and stability of ABX 3 perovskite compounds.In addition, the geometric argument ii) allows for some flexibility. For a perfectly cubic perovskite, the (effective) ionic radii r must fulfill the relation of Goldschmidt's tolerance factor 2( ) 1 A X B X t r r r r = + + = . [30,31] However, perovskites can exist also with t being not ideal, usually in a range of about 0.75 < t < 1.05. [8] Whenever t ≠ 1, the crystal distorts from an ideal cubic lattice, usually in form of off-center displacements, octahedral rotations, or a combination of both. The classification of Glazer [32,33] can be used to describe such distortions from a perfectly cubic perovskite. [34] It is further possible that ABX 3 compounds are stable whose t does not fall into the interval that is required for the perovskite crystal structure. In these cases that are no longer stabilized by deformations and tilting, one observes other phases where the connectivity of BX 6Materials science evolves to a state where the composition and structure of a crystal can be controlled almost at will. Given that a composition meets basic requirements of stoichiometry, steric demands, and charge neutrality, researchers are now able to investigate a wide range of compounds theoretically and, under various experimental conditions, select the constituting fragments of a crystal. One intriguing playground for such materials design is the perovskite structure. While a game of mixing and matching ions has been pla...

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“…A first candidate for the spheroidal cation would be tetramethylammonium (TMA + , Table 1), which is much larger in size than MA + and requires an expanded host framework comprising polyatomic bridges. For example, the triazide perovskite structures TMAMn(N 3 ) 3 , 16,23 TMACd(N 3 ) 3 , 27 and TMACa(N 3 ) 3 28 are known. In their LT phases, the host framework becomes distorted to achieve close packing with the stationary TMA + bearing a tetrahedral profile.…”

Section: Introductionmentioning

confidence: 99%

Order–Disorder Transition of a Rigid Cage Cation Embedded in a Cubic Perovskite

Shi

Fang

et al. 2021

Preprint

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The structure and properties of organic–inorganic hybrid perovskites are impacted by the order–disorder transition, whose driving forces from the organic cation and the inorganic framework cannot easily be disentangled. Herein, we report the design, synthesis and properties of a cage-in-framework perovskite AthMn(N3)3, where Ath+ is an organic cation 4-azatricyclo[2.2.1.02,6]heptanium. Ath+ features a rigid and spheroidal profile, such that its molecular reorientation does not alter the cubic lattice symmetry of the Mn(N3)3− host framework. This pure order–disorder transition is well characterized by NMR, crystallography, and calorimetry, and associated with the realignment of Ath+ dipole from antiferroelectric to paraelectric. As a result, an abrupt rise in the dielectric constant was observed during the transition. Our work introduces a new family of perovskite structures and provides direct insights to the order–disorder transition of hybrid materials.

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Tetramethylammonium-calcium-triazid. Darstellung und Kristallstruktur

Cited by 23 publications

References 3 publications

Tilts and shifts in molecular perovskites

Tilts and shifts in molecular perovskites

Mix and Match: Organic and Inorganic Ions in the Perovskite Lattice

Order–Disorder Transition of a Rigid Cage Cation Embedded in a Cubic Perovskite

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