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for synthetic compounds see .
Perovskite (pronunciation: ) is a
composed of , with the chemical formula 3. The mineral was discovered in the
in 1839 and is named after Russian mineralogist
It lends its name to the class of compounds which have the same type of
as CaTiO3 (XIIA2+VIB4+X2-3) known as the . The perovskite crystal structure was first described by
in 1926, in his work on tolerance factors. The crystal structure was later published in 1945 from
Found in the Earth’s , perovskite’s occurrence at
is restricted to the under-saturated
rocks and , due to the instability in a
with . Perovskite occurs as small
to subhedral crystals filling interstices between the rock-forming silicates.
Perovskite is found in
at , , in altered blocks of
ejected from , in
and . and as an accessory mineral in alkaline and
, , melilitite,
and rare . Perovskite is a common mineral in the
found in some .
A -bearing variety, knopite, (Ca,Ce,Na)(Ti,Fe)O3) is found in alkali intrusive rocks in the
and near , . A -bearing variety, dysanalyte, occurs in
near Schelingen, , .
The stability of perovskite in
is limited by its reaction relation with . In
perovskite and sphene are not found together, the only exception being in an [ – ] from .
Perovskites have a cubic structure with general formula of ABO
3. In this structure, an A-site ion, on the corners of the lattice, is usually an alkaline earth or . B site ions, on the center of the lattice, could be 3d, 4d, and 5d
elements. A large number of metallic elements are stable in the perovskite structure, if the tolerance factor t is in the range of 0.75 – 1.0.
where RA, RB and RO are the ionic radii of A and B site elements and oxygen, respectively.
Perovskites have sub-metallic to
, colorless , cube like structure along with imperfect
and brittle tenacity. Colors include black, brown, gray, orange to yellow. Crystals of perovskite appear as cubes, but are pseudocubic and crystallize in the
system. Perovskite crystals hav however, galena has a better metallic luster, greater density, perfect cleavage and true cubic symmetry.
Perovskites may be structured in layers, with the above ABO
3 structure separated by thin sheets of intrusive material. Different forms of intrusions, based on the chemical makeup of the intrusion, are defined as:
: the intruding layer is composed of a [Bi
2]2+ ion, occurring every n ABO
3 layers, leading to an overall chemical formula of [Bi
7. Their oxide ion-conducting properties were first discovered in the 1970s by Takahashi et al., and they have been used for this purpose ever since.
Dion-Jacobson phase: the intruding layer is composed of an alkali metal (M) every n ABO
3 layers, giving the overall formula as M10+A
: the simplest of the phases, the intruding layer occurs between every one (n = 1) or two (n = 2) layers of the ABO
3 lattice. Ruddlesden-Popper phases have a similar relationship to perovskites in terms of atomic radii of elements with A typically being large (such as La or Sr) with the B ion being much smaller typically a transition metal (such as Mn, Co or Ni).
. Webmineral
Anthony, John W.; Bideaux, Richard A.; Bladh, Kenneth W. and Nichols, Monte C. (Eds.) . Handbook of Mineralogy. Mineralogical Society of America, Chantilly, VA
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Veksler, I.V.; Teptelev, M.P. (1990). "Conditions for crystallization and concentration of perovskite-type minerals in alkaline magmas". Lithos 26: 177–189. :. :.
Luxová, J ?ulcová, P Trojan, M. (2008).
(PDF). Journal of Thermal Analysis and Calorimetry 93 (3): 823–827. :.
Lufaso, Michael W.; Woodward, Patrick M. (2004). "Jahn–Teller distortions, cation ordering and octahedral tilting in perovskites". Acta Crystallographica Section B Structural Science 60: 10–20. :.
Chakhmouradian, Anton R. and Mitchell, Roger H. (1998).
(PDF). The Canadian Mineralogist 36: 953–969.
Lemanov, V; Sotnikov, A.V.; Smirnova, E.P.; Weihnacht, M.; Kunze, R. (1999). "Perovskite CaTiO3 as an incipient ferroelectric". Solid State Communications 110 (11): 611–614. :. :.
Wenk, Hans-R Bulakh, Andrei (2004). . New York, NY: Cambridge University Press. p. 413.  .
Golschmidt, V M (1926). "Die Gesetze der Krystallochemie". Die Naturwissenschaften 21 (21): 477–485. :. :.
Megaw, Helen (1945). "Crystal Structure of Barium Titanate". Nature 155 (3938): 484–485. :. :.
Palache, Charles, Harry Berman and Clifford Frondel, 1944, Dana's System of Mineralogy Vol. 1, Wiley, 7th ed. p. 733
Deer, William A Howie, Robert A Zussman, J. (1992). . Longman Scientific Technical.  .
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Cava, Robert J. . Princeton University 2013.
Kendall, K. R.; Navas, C.; Thomas, J. K.; Zur Loye, H. C. (1996). "Recent Developments in Oxide Ion Conductors: Aurivillius Phases". Chemistry of Materials 8 (3): 642–649. :.
MUNNINGS, C; SKINNER, S; AMOW, G; WHITFIELD, P; DAVIDSON, I (15 October 2006). "Structure, stability and electrical properties of the La(2-x)SrxMnO4±δ solid solution series". Solid State Ionics 177 (19-25): . :.
Munnings, Christopher N.; Sayers, R Stuart, Paul A.; Skinner, Stephen J. (January 2012). "Structural transformation and oxidation of Sr2MnO3.5+x determined by in-situ neutron powder diffraction". Solid State Sciences 14 (1): 48–53. :.
Amow, G.; Whitfield, P.S.; Davidson, I.J.; Hammond, R.P.; Munnings, C.N.; Skinner, S.J. (January 2004). "Structural and sintering characteristics of the La2Ni1-xCoxO4+δ series". Ceramics International 30 (7): . :.
Amow, G.; Whitfield, P. S.; Davidson, J.; Hammond, R. P.; Munnings, C.; Skinner, S. (11 February 2011). "Structural and Physical Property Trends of the Hyperstoichiometric Series, La2Ni(1-x)CoxO4+δ". MRS Proceedings 755. :.
: Hidden categories:Phys. Rev. B 72, 05) - Neutron diffraction, magnetization, and ESR studies of pseudocubic ${\mathrm{Nd}}_{0.75}{\mathrm{Ba}}_{0.25}{\mathrm{MnO}}_{3}$ and its critical behavior above ${T}_{C}$
Results of structural neutron diffraction study, magnetization, and electron spin resonance (ESR) measurements are presented for insulating Nd1-xBaxMnO3(x=0.25) with the Curie temperature TC≈129K. Detailed analysis of the data is performed by using Pbnm space group in a temperature range 4.2–300 K. The compound is found to exhibit the Jahn-Teller (JT) transition at TJT~250K. The character of the coherent JT distortions and their temperature evolution differ from those of the x=0.23 manganite. The field cooled magnetization data are in reasonable agreement with the predictions for a three-dimensional (3D) isotropic ferromagnet above TC. These measurements, however, reveal a difference between the field cooled and zero field cooled data in the paramagnetic region. The ESR results also correspond with behavior of a 3D isotropic ferromagnet above T*≈143K[τ*≈0.12?τ&1,τ=(T-TC)∕TC]. The T-dependence of the ESR linewidth is found to be proportional to [Tχ(T)]-1, where χ(T) is the susceptibility. This uncritical behavior results from the anisotropic spin interactions that can be attributed to the Dzyaloshinsky-Moria (DM) coupling. The critical enhancement is not observed. It can be explained by the strong uncritical contribution to the linewidth, and suppression of the critical enhancement by a magnetic field. The different temperature treatments (slow/fast cooling/heating, with/without external magnetic field) of the sample reveal a temperature hysteresis of the ESR spectra below T* indicating an anomalous response in the paramagnetic region. The study of the magnetic phase transition in the x=0.23 and 0.25 manganites suggests change in its character from second to first order at T*. The conventional free energy including the magnetization and magnetic field is not found to describe this first order transition. This suggests that the charge, orbital, and JT phonon degrees of freedom, in addition to magnetization, may be the critical variables, the unusual character of the transition being determined by their coupling. The unconventional critical behavior is attributed to an orbital liquid metallic phase that begins to coexist with the initial orbital ordered phase below T*.DOI:http://dx.doi.org/10.1103/PhysRevB.72.134427Authors & Affiliations
, , , , , and Petersburg Nuclear Physics Institute, Gatchina, Leningrad District, 188300, Russia and Institute of Physics of Solids and Semiconductors, National Academy of Sciences, ul. P. Brovki street 17, Minsk, 220072, BelarusArticle Text (Subscription Required)
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Authorization RequiredOther OptionsDownload & ShareImagesFigure 1The neutron diffraction pattern, calculated profile, and residual curve for Nd0.75Ba0.25MnO3 at room temperature. The inset shows the wide and weak monoclinic peaks at the small angles.Figure 2Temperature dependences of the structural parameters a,b,c [panel (a)]; volume of the unit cell V and magnetic moment of the sample per Mn ion [panel (b)]; the Mn-O bond lengths [panel (c)]; and the Mn-O-Mn angles [panel (d)].Figure 3Temperature dependence of the magnetization for the cooling and heating regimes under H=1kOe. Panel (a) shows these dependencies in the full temperature range 6–300 K. Inset (1) displays fit of the M-1(T) measured in the ZFC regime to the function τγ∕CH+4πN∕H. The fitting parameters are found to be 1∕CH=3.98(3)g∕emu and γ=1.39(1) at N=1∕3. Inset (2) represents fit of the ZFCM(τ)∕Hint to expressions (2), (3) (see the text) in T range TC–261 K. Panel (b) shows the relative difference δM vs T in the T range 80–300 K. The insert in (b) displays the M(T) curves registered in the ZFC and FC regimes in T range 140–180 K.Figure 4The ESR spectra for the different T scans at some close temperatures: cooling [solid line, panels (a)–(d)], heating after fast cooling [dashed line, panels (a)–(c)], cooling under H=4kOe [dotted line, panels (a) and (d)]. Panels (a) and (c) also represent the fit of the spectra recorded on cooling by a Lorenzian (dash-dotted line).Figure 5Temperature dependencies of parameters of the ESR spectra for different T treatments of the sample: cooling (full symbols) and heating (open symbols) under H=0 (squares) and H=4kOe (triangles); heating after fast cooling (stars). Panel (a) displays the spin relaxation rate Γ vs temperature. Inset shows Γ(τ) dependence on cooling, and its fit as described in the text. Panel (b) represents amplitudes Aas(T) of the spectra vs T. Inset shows fit of Aas(τ)∝χ(τ) to the scaling law.AuthorsRefereesLibrariansStudentsAPS MembersISSN
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Theoretical Description of Pseudocubic Manganite
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Theoretical Description of Pseudocubic Manganite
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