Die Gesetze der Krystallochemie

Goldschmidt, V. M.

doi:10.1007/bf01507527

Cited by 3,007 publications

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“…The stability of perovskite compound based on ABO 3 formula is often discussed in reference to Goldschmidt's tolerance factor t. The tolerance factor for Bi 0.825 A 0.175 FeO 3 (A = La, Pb) can be written as [31]: [32,33]. It is now well established that, ferroic order and spontaneous polarization in BFO mainly result from the Bi 3+ stereochemical 6s 2 lone pair electrons.…”

Section: X-ray Diffractionmentioning

confidence: 99%

Rare earth (La) and metal ion (Pb) substitution induced structural and multiferroic properties of bismuth ferrite

2015

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Abstract:In this study, bulk samples of multiferroic with compositional formula, BiFeO 3 and Bi 0.825 A 0.175 FeO 3 (A = La, Pb), were synthesized by solid state reaction route. X-ray diffraction (XRD) along with the Rietveld refinement revealed the distorted rhombohedral (R3c) structure for pristine BiFeO 3 and Bi 0.825 La 0.175 FeO 3 and tetragonal (P4/mmm) for Bi 0.825 Pb 0.175 FeO 3 ceramic. To support the structural results, bond length between atoms for both of the compounds was calculated. A change in Raman mode position in BiFeO 3 (BFO) has been observed with La and Pb substitution from Raman scattering measurements and also recommended a structural change with rare earth and metal ion substitution at Bi site. From the frequency dependent dielectric constant and dielectric loss plots, a decrease in dielectric values with increase in frequency was observed for both of the samples. For microelectronic devices, porous ceramics with lower value of dielectric constant are most useful. Thus, further studies are also needed to carefully tune the magnetoelectric properties and structural distortion after La/Pb substitution in BFO.

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Section: X-ray Diffractionmentioning

confidence: 99%

Rare earth (La) and metal ion (Pb) substitution induced structural and multiferroic properties of bismuth ferrite

2015

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“…Also, the energy levels of the 3d electrons of Fe 2+ and Co 2+ at the distorted dodecahedral site of perovskites are further separated. (Goldschmidt, 1926). Solid circles: compounds which transform from orthorhombic perovskite to CaIrO 3 -type post-perovskite with increasing pressure.…”

Section: Figure Captionsmentioning

confidence: 99%

Stability of the perovskite structure and possibility of the transition to the post-perovskite structure in CaSiO3, FeSiO3, MnSiO3 and CoSiO3

Fujino

Nishio–Hamane

Suzuki

et al. 2009

Physics of the Earth and Planetary Interiors

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High pressure and high temperature experiments on CaSiO 3 , FeSiO 3 , MnSiO 3 and CoSiO 3 using a laser-heated diamond anvil cell combined with synchrotron X-ray diffraction were conducted to explore the perovskite structure of these compounds and the transition to the post-perovskite structure. The experimental results revealed that MnSiO 3 has a perovskite structure from relatively low pressure (ca. 20 GPa) similarly to CaSiO 3 , while the stable forms of FeSiO 3 and CoSiO 3 are mixtures of mono-oxide (NaCl structure) + high pressure polymorph of SiO 2 even at very high pressure and temperature (149 GPa and 1800 K for FeSiO 3 and 79 GPa and 2000 K for CoSiO 3 ). This strongly suggests that the crystal field stabilization energy (CFSE) of Fe 2+ with six 3d electrons and Co 2+ with seven 3d electrons at the octahedral site of mono-oxides favors a mixture of mono-oxide + SiO 2 over perovskite where Fe 2+ and Co 2+ would occupy the distorted dodecahedral sites having a smaller CFSE (Mn 2+ has five 3d electrons and has no CFSE).The structural characteristics that the orthorhombic distortion of MnSiO 3 perovskite decreases with pressure and the tolerance factor of CaSiO 3 perovskite (0.99) is far from the orthorhombic range suggest that both MnSiO 3 and CaSiO 3 perovskites will not transform to the CaIrO 3 -type post-perovskite structure even at the Earth's core-mantle boundary conditions, although CaSiO 3 perovskite has a potentiality to transform to the CaIrO 3 -type post-perovskite structure at still higher pressure as long as another type of transformation does not occur.

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“…The A ion, however, has a large influence on whether and how the crystal structure is distorted from the cubic structure. Quite often, the type of distortion can be predicted by the basic Goldschmidt tolerance factor 7 , t, which can be calculated from ionic radii, r, by equation 1.…”

Section: Introductionmentioning

confidence: 99%

Phase stability of theSrMnO3hexagonal perovskite system at high pressure and temperature

et al. 2014

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SrMnO 3 is a perovskite compound which, unlike most perovskites, can be synthesized in three different but closely related polymorphs. In this paper, the first experimental equation of state of the 6H polymorphs is reported. The experimentally determined bulk modulus of SrMnO 3 increases from 115.6(11) GPa in the 4H polymorph to 143.7(17) GPa in the 6H polymorph, while DFT calculations predict a further increase to 172.5(4) GPa in the 3C polymorph. The first in situ observations of transformations between the three known polymorphs, under high pressure and high temperature conditions are also reported. The results are compared with extensive DFT calculations and literature, and it is demonstrated that the 6H polymorph is the thermodynamically stable phase between 5.9(3) and 18.1(2) GPa at zero kelvin. The effect of possible oxygen sub-stoichiometry is also explored, used DFT. Finally, the findings are combined with the existing knowledge of the phase behavior in this system to outline where further knowledge needs to be collected before a PT phase diagram can be constructed for this system. I. INTRODUCTIONInorganic compounds with the formula ABX 3 very often crystallize in the well-known perovskite structure, or distorted derivatives thereof. In the ideal cubic structure, the unit cell can be described by an AX 3 cubic close-packed layer, with B ions in the octahedral holes that are surrounded only by X anions. The packing sequence is abc, a being the first hexagonal layer, b the second layer that covers half the holes in a, and c the third placed on top of b to cover the other half. This class of materials covers a wide range of technologically relevant compounds that can display piezoelectric 1 , ferroelectric 2 , (anti)ferromagnetic 3 , catalytic 4 , semiconducting 5 , metallic 6 or insulating 6 behavior. Due to the widespread use of materials with this structure, it is worthwhile trying to gain a deeper insight into the factors governing phase stability in this type of system.

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Die Gesetze der Krystallochemie

Cited by 3,007 publications

References 0 publications

Rare earth (La) and metal ion (Pb) substitution induced structural and multiferroic properties of bismuth ferrite

Rare earth (La) and metal ion (Pb) substitution induced structural and multiferroic properties of bismuth ferrite

Stability of the perovskite structure and possibility of the transition to the post-perovskite structure in CaSiO3, FeSiO3, MnSiO3 and CoSiO3

Phase stability of theSrMnO3hexagonal perovskite system at high pressure and temperature

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