Space Group Immm Research Articles

A-site-ordered quadruple perovskite manganite CeMn7O12 with trivalent cations

A-site-ordered quadruple perovskite CeMn7O12 – the first ternary oxide in the Ce–Mn–O system – was synthesized at high pressure of 6 ​GPa and high temperature of about 1670 ​K, and its structural, magnetic, and dielectric properties were investigated. CeMn7O12 crystallizes in space group Im-3 above 649 ​K, and in space group I2/m below 649 ​K. No other structural phase transitions were found down to 10 ​K. Crystal structures were investigated using synchrotron X-ray powder diffraction (a ​= ​7.50069 ​Å, b ​= ​7.36836 ​Å, c ​= ​7.49086 ​Å, β ​= ​91.2125° at 295 ​K and a ​= ​7.47367 ​Å ​at 700 ​K), and the structural parameters (Ce–O bond lengths) suggest the Ce3+ oxidation state giving the charge distribution as Ce3+Mn3+7O12. CeMn7O12 shows one long-range-ordered ferrimagnetic transition at TN ​= ​78 ​K accompanied by very weak kink-like dielectric anomalies. Strong dielectric relaxation due to extrinsic processes was observed near 18–35 ​K.

Crystal Structure of Baryum Dicobalt Iron (III) Three (Orthophosphate) Belonging to <i>α</i>-CrPO<SUB>4</SUB> Family

The new compound, BaCo2Fe(PO4)3, has been synthesized by solid state reaction. The analysis by X-ray diffraction technique showed that it crystallizes in the orthorhombic system with the space group Imma. The structure is closely linked to that of α-CrPO4 type structure. In this structure, two oxygen atoms (O1, O2) are in general position and the others in special positions. The three-dimensional network of the crystal structure is made up of two types of chains running to [001] direction. The first chain is originated from two edge-sharing CoO6 octahedra leading to the formation of Co2O10 dimers that are connected to two PO4 tetrahedra by a common edge. The junction of FeO6 octahedra and PO4 tetrahedra sharing vertices allowed to built the second chain. These chains are linked together by common vertices of tetrahedra PO4 to form an open three-dimensional framework that delimits two types of tunnels parallel to [010] and [100] where the BaII cations are located. Indeed, each Barium cation is surrounded by eight oxygen atoms.

The Tl2SnSe3-CdSe System and the Crystal Structure of the Tl2CdSnSe4 Compound

Component interaction at the Tl2Se-CdSe-SnSe2 section was investigated by x-ray diffraction and differential thermal analysis, and the phase diagram was constructed. The existence of a new quaternary compound Tl2CdSnSe4 with two polymorphous modifications was established. The crystal structure of the low-temperature modification of Tl2CdSnSe4 was determined. The compound crystallizes in space group I-42m, Pearson symbol tI16, a = 0.80490(6) nm, c = 0.68573(8) nm, RI = 0.0815.

Insulator-Metal Transition and Topological Superconductivity in UTe_{2} from a First-Principles Calculation.

We theoretically study superconductivity in UTe_{2}, which is a recently discovered strong candidate for an odd-parity spin-triplet superconductor. Theoretical studies for this compound faced difficulty because first-principles calculations predict an insulating electronic state, incompatible with superconducting instability. To overcome this problem, we take into account electron correlation effects by a GGA+U method and show the insulator-metal transition by Coulomb interaction. Using Fermi surfaces obtained as a function of U, we clarify topological properties of possible superconducting states.Fermi surface formulas for the three-dimensional winding number and three two-dimensional Z_{2} numbers indicate topological superconductivity at an intermediate U for all the odd-parity pairing symmetry in the Immm space group. Symmetry and topology of superconducting gap nodes are analyzed and the gap structure of UTe_{2} is predicted. Topologically protected low-energy excitations are highlighted, and experiments by bulk and surface probes are proposed to link Fermi surfaces and pairing symmetry. Based on the results, we also discuss multiple superconducting phases under magnetic fields, which were implied by recent experiments.

High-pressure synthesis and spin glass behavior of a Mn/Ir disordered quadruple perovskite CaCu3Mn2Ir2O12

A new 3d-5d hybridized quadruple perovskite oxide, CaCu3Mn2Ir2O12, was synthesized by high-pressure and high-temperature methods. The Rietveld structure analysis reveals that the compound crystallizes in an -type perovskite structure with space group Im-3, where the Ca and Cu are 1:3 ordered at fixed atomic positions. At the B site the 3d Mn and the 5d Ir ions are disorderly distributed due to the rare equal +4 charge states for both of them as determined by x-ray absorption spectroscopy. The competing antiferromagnetic and ferromagnetic interactions among Cu2+, Mn4+, and Ir4+ ions give rise to spin glass behavior, which follows a conventional dynamical slowing down model.

Properties of NaCu3Ti3NbO12 based-ceramics doped with nanopowders

In this work, the properties of NaCu3Ti3NbO12 based ceramics preparing by mixed oxide method were studied. The starting materials including Na2CO3, CuO, TiO2 and Nb2O5 were mixed by ball milling for 24 hours with stoichiometry, calcined at 950 °C for 24 hours and were doped with (0–2.0 vol%) MgO, Al2O3 and ZrO2 nanopowders. Then, the mixed powder was pressed into a disc shape. The green bodies were sintered at 975–1025 °C for 10 hours. Phase formation was investigated by XRD and microstructure by SEM. The body-centered cubic perovskite-related structure of space group Im-3 and small amount of second phase were detected. The normal grain growth is observed and shown rectangular grain shape. Density of the sintered samples was measured by Archimedes’s method using distilled water as the fluid medium. The highest density of NCTNO and NCTNO/Al2O3 ceramics were found at 1025 °C sintered temperature and 1000 °C for NCTNO/MgO and NCTNO/ZrO2 samples. Dielectric constant of the samples was examined using an LCR meter and the mechanical properties of samples were investigated by Vickers microhardness tester. The addition of nanopowders can be improved the mechanical property and 1.0 vol%ZrO2 doping sample showed the highest the dielectric constant.

Depicting the crystal structure of fibrous ferrierite from British Columbia using a combined synchrotron techniques approach.

The ferrierite crystal structure has often been subject to discussion because of the possible lowering of symmetry from the space group Immm. It mainly occurs in nature with a fibrous crystal habit, and because of the existence of line/planar defects in the framework, texture and preferred orientation effects it has been difficult to obtain an exact crystallographic model based only on the results from powder diffraction data. Therefore, nano-single-crystal diffraction and tomography data have been combined in order to improve the refinement with a meaningful model. High-quality single-crystal data, providing reliable structural information, and tomography images have been used as input for a Rietveld refinement which took into account a phenomenological description of stacking disorder and the analytical description of the preferred orientation, by means of spherical harmonics for strong texture effects. This is one of the first examples of application of synchrotron nano-diffraction for the structure solution of fibrous minerals of micrometre to nanometre size. The high quality of the crystals allowed collection of single-crystal X-ray diffraction data of up to 0.6 Å resolution, leading to an unambiguous solution and precise anisotropic refinement. Nano-single-crystal diffraction and phase contrast tomography data were collected at ID11 and the high-resolution powder diffraction patterns at ID22 of the European Synchrotron Radiation Facility. This detailed crystallographic characterization provides a basis for understanding the potential of ferrierite for toxicity and carcinogenicity.

Incompatible magnetic and dielectric properties of BiCu3-xMnxTi4-yMyO12 (x = 0 & 0.5; y = 1 & 1.5 and M = Fe & Mn)

Here we report ambient pressure synthesis, magnetic and dielectric properties of BiCu3Ti3(Fe/Mn)O12 and BiCu2.5Mn0.5Ti2.5Fe1.5O12. Both the samples are crystallized in a cubic Im-3 space group. The antiferromagnetic ground state of A-site copper in Bi2/3Cu3Ti4O12 is differently affected by substitution of nonmagnetic Ti4+ by magnetic Fe and Mn ions in B-site. In contrast to the Mn substitution, the antiferromagnetic ordering of A-site Cu is robust towards Fe substitution. The substitution of iron for Ti4+ initially weakens the antiferromagnetic structure of A-site Cu and eventually it results in the crossover from antiferromagnetic to ferrimagnetic state, whereas the Mn substitution quickly turns antiferromagnetic to ferrimagnetic state. For x > 1.0 Fe-doped sample and low Mn-doped samples exhibit phase separation where the ferromagnetic like phase coexists with antiferromagnetic phase. The glassy magnetic state is realized for x = 1.0 Fe doped sample. The magnetic ground state strongly influences the dielectric behavior of the samples. Near room temperature the dielectric constant value is ~2000 for BiCu3Ti3FeO12, whereas for BiCu2.5Mn0.5Ti2.5Fe1.5O12 the value is much lower (<600) with higher dielectric loss. The leaky nature in magnetically phase separated BiCu2.5Mn0.5Ti2.5Fe1.5O12 can be ascribed to the opening of conducting ferrimagnetic channels. The present investigation revealed that in quadruple perovskite the magnetic and dielectric properties are incompatible where improvement of magnetic response eventually suppresses the dielectric behavior.

Pressure-induced structural transitions and metallization in hollow ZnMn2O4 microspheres

High-pressure in situ angle dispersive X-ray diffraction (ADXRD) measurements combined with first-principles calculations were performed on hollow ZnMn2O4 microspheres up to 43.5 GPa at room temperature, and two high-pressure phases emerged at 15.9 GPa. Phase III was assigned to the CaMn2O4 type structure (space group Pbcm). It is supposed that phase II probably has a MgAl2S4 inverted spinel type structure (space group Imma). Moreover, phase I, phase II and phase III were probably coexisted when pressure was released. The compressional behaviors of phase I (space group I41/amd) and phase III were all determined. Besides, based on electronic band structure calculations, it was uncovered that phase I probably experiences a pressure-induced electronic topological transition (ETT) to a semimetallic state upon pressure, and phase III is a semimetallic state. Our results show that pressure play a dramatic role in tuning ZnMn2O4’s crystalline structures, electrical behavior and spin-state.

Unified View of the Local Cation-Ordered State in Inverse Spinel Oxides.

Cation ordering/disordering in spinel oxides plays an essential role in the rich physical and chemical properties which are hallmarks of the structural archetype. A variety of cation-ordering motifs have been reported for spinel oxides with multiple cations residing on the octahedral site (or B-site). This has attracted tremendous attention from both experimental and theoretical communities in the last few decades. However, no unified view has been reached, presumably due to the richness of cation species and corresponding complex arrangements emergent in this large family of compounds. In this report, local cation-ordered ground states of (inverse) spinel oxides with two different cations on the octahedral site have been thoroughly investigated using neutron and X-ray total scattering, and a comprehensive theory has been proposed to explain the commonly observed cation-ordered polymorphs. It is found that a cation-zigzag-ordered structure (space group P4122) is the ground state for inverse spinel oxides with a pure or strong ionic lattice, while a cation-linear-ordered arrangement (space group Imma) emerges when one of the B-site cations forms very strong directional covalent bonds with lattice oxygen. The degree and length scale of cation ordering is strongly correlated with the charge and ionic radius difference between the two octahedral site cations. More complicated cation ordering schemes can be formed when there is a concomitant charge and orbital ordering which fall on a similar energy scale. This can lead to the formation of orbital-driven cation clusters or the broad concept of "molecules" in solid- state compounds. It is expected these findings will help to better understand the observed physical properties of spinel oxides and thus facilitate design strategies for improved functional materials.

Structure of Cubic Al73.8Pd13.6Fe12.6 Phase with High Al Content

A cubic ternary phase Al73.8Pd13.6Fe12.6 (designated C′ phase), with very high Al content (Al/TM = 2.82, TM denotes transition metal) was prepared by spark plasma sintering (SPS). Its crystal structure was determined by combing single-crystal X-ray diffraction (SXRD) and scanning electron microscope (SEM) equipped with energy dispersive X-ray spectroscopy (EDS) measurements. The crystal structure of the new phase can be described with a small unit cell (a = 7.6403(2) Å; space group Pm3, No. 200) as that of Al2.63Rh (a = 7.6692(1) Å; space group P23, No. 195) while different from those of the reported Al39Pd21Fe2 (a = 15.515(1) Å; space group Fm3, No. 202) and Al69Pd17Fe14 (a = 15.3982(2) Å; space group Im3, No. 204) compounds, which both adopt a double length unit cell in the Al–Pd–Fe system. The mechanism of distributing more Al atoms in the new phase was compared with that of the Al2.63Rh phase by analyzing their site symmetry and the corresponding site of occupancies (SOF). Furthermore, relations of the C′ phase to the reported Al69Pd17Fe14 (designated C1 phase) and Al39Pd21Fe2 (designated C2 phase) phases were investigated by analyzing their building units with the “nanocluster” method in the ToposPro package.

Preservation of large low temperature magnetocaloric effect in metamagnetic intermetallic compounds RCu2 (R = Gd, Tb, Dy, Ho and Er) upon rapid solidification

In this work, magnetic and magnetocaloric properties of melt-spun RCu2 (R = Gd, Tb, Dy, Ho and Er) compounds have been studied. The melt-spun samples have formed in the same orthorhombic crystal structure (space group Imma, no. 74) as that of the arc-melted samples but with a development of crystallographic texture and micron-size grains. The melt-spun ribbons of RCu2 (R = Gd, Tb, Dy, Ho and Er) order antiferromagnetically at 43 K, 51 K, 28 K, 10 K and 11 K (TN) respectively. The ordering temperatures are almost the same as that of the arc-melted samples. The RCu2 compounds show one or more field induced transitions below TN. Therefore, a normal magnetocaloric effect is observed in these compounds when the magnetic field change is larger than the metamagnetic critical field and inverse magnetocaloric effect is observed for smaller field changes. The microgranularity does not seem to smear out the metamagnetic transition. The maximum of isothermal magnetic entropy change, ΔSmmax, is about −2.1 Jkg−1K−1, -5.5 Jkg−1K−1, -5.2 Jkg−1K−1, -17.2 Jkg−1K−1 and -11.7 Jkg−1K−1 respectively for the melt-spun RCu2 (R = Gd, Tb, Dy, Ho and Er) samples for 50 kOe field change. The refrigeration capacity is found to be 40 Jkg-1, 160 Jkg-1, 166 Jkg-1, 230 Jkg-1 and 207 Jkg-1 respectively, for the above samples. These values are nearly the same as that of the arc-melted counterparts. Thus the large magnetocaloric effect in the temperature range of 10 K–70 K make these melt-spun RCu2 samples potential materials for low temperature refrigeration applications. The results also ascertain melt-spinning process as an alternate technique for the production of magnetocaloric alloys and intermetallics.

Structural Study of Vanadium Substituted Mo2NiB2

Vanadium substituted Mo2–xNi1–xV2xB2 (x = 0 and 0.45) was prepared by reaction boronizing sintering and investigated using X-ray powder diffraction. Structure of Vanadium substituted Mo2–xNi1–xV2xB2 was determined using the Rietveld method. The results show that the crystal structure of vanadium substituted Mo2NiB2 has changed from orthorhombic to tetragonal. The crystal structure of Mo2NiB2 belongs to the structure type W2CoB2 with space group Immm (No. 71). The unit-cell lattice parameters are a = 7.0914(2) A, b = 4.5639(9) A, c = 3.1787(8) A. The reliability factor for the refinement is Rp = 6.74% and Rwp = 8.52%. The crystal structure of vanadium substituted Mo2NiB2 belongs to space group P4/mbm (No. 127). The lattice parameters are a = b = 5.8244(5) A, c = 3.1239(6) A. The reliability factor is Rp = 5.69% and Rwp = 7.41%.

The Y–Mg–Co ternary system: alloys synthesis, phase diagram at 500 °C and crystal structure of the new compounds

The ternary phase diagram of the Y–Mg–Co system have been studied at 500 °C by combining X-ray diffraction (XRD), energy dispersive X-ray (EDX) and wavelength dispersive X-ray (WDX). The existence of four ternary compounds Y4MgCo (Gd4RhIn-type), Y9Mg30Co2 (own structure type), Y6Mg9Co2 (own structure type) and Y9Mg4Co (Hf9Mo4B-type) was confirmed. For all of them homogeneity range has been defined. Two new ternary compounds were identified in this work: Y12MgCo5 (Ho12BiCo5-type, orthorhombic, Space Group Immm, a = 9.5078(5)–9.538(4) Å, b = 9.4741(4)–9.531(4) Å, c = 10.0217(5)–10.061(5) Å) and ∼Y52Mg3Co45 (unknown crystal structure). YCo3 and YCo2 compounds form extended solid solutions where maximum solubility of Mg is 8 and 16 at. %, respectively. The solubility of Mg in YCo2 leads to a structure change from MgCu2-type to SnMgCu4-type. It was also found that binary MgCo2 compound dissolve 4.9 at. % Y and YMg can dissolve up to 2.5 at. % of Co. New binary Y5Co6 compound was determined with two structures: α – low- and β – high-temperature. The α-Y5Co6 was indexed as monoclinic (a = 22.214 Å, b = 7.509 Å, c = 5.885 Å and β = 108.22°), while β-Y5Co6 crystalizes in the orthorhombic structure (space group Cmcm) with lattice parameters a = 4.104(1) Å, b = 10.246(1) Å and c = 20.336(3) Å. Detailed crystallographic data were collected for the Y5Mg0.07(1)Co5.93(1) and Y12MgCo5 single crystals. The metallic type bonding for Y12MgCo5 was confirmed by electronic structure calculations.

High-pressure synthesis of A-site ordered perovskite CaMn3(Fe3Mn)O12 and sequential long-range antiferromagnetic ordering and spin glass transition

An AA’3B4O12-type perovskite oxide CaMn3(Fe3Mn)O12 was synthesized at 8 GPa and 1473 K. X-ray diffraction shows a cubic crystal structure with space group Im-3. The charge states are verified by soft x-ray absorption spectroscopy to be CaMn3+3(Fe3+3Mn4+)O12, where the Ca2+ and Mn3+ are 1:3 ordered respectively at A and A′ sites, while the Mn4+ and Fe3+ are disorderly distributed at B site. The spin interaction of A′-site Mn3+ ions causes a long-range antiferromagnetic phase transition at about 39 K. Subsequently, a spin glass transition is found to occur around 14 K due to the randomly distributed Fe3+ and Mn4+ at B site. Moreover, the spin glass behavior follows a dynamic scaling power law. The temperature dependent resistivity can be well fitted by a 3D Mott variable-range hopping model, indicating the insulating nature of CaMn3(Fe3Mn)O12 due to the strong electron correlation effects.

Magnetic ordering of Ho6Co2Ga-type {Gd, Tb, Dy}6Co2.2Al0.8 and Tb6Co2Al compounds by magnetization and neutron diffraction study

The magnetic ordering of polycrystalline Ho6Co2Ga-type Gd6Co2.2Al0.8, Tb6Co2.2Al0.8, Tb6Co2Al and Dy6Co2.2Al0.8 (space group Immm, N 71, oI36) has been established using magnetic measurements and the magnetic structure of Tb6Co2.2Al0.8 has been resolved by the neutron diffraction study. Gd6Co2.2Al0.8 exhibits field sensitive ferro-antiferromagnetic ordering, meanwhile Tb6Co2.2Al0.8, Tb6Co2Al and Dy6Co2.2Al0.8 are antiferromagnets with metamagnetic transformation of magnetic ordering. Gd6Co2.2Al0.8 is soft ferromagnet, whereas Tb6Co2.2Al0.8, Tb6Co2Al and Dy6Co2.2Al0.8 exhibit low-temperature weak permanent magnet properties. From these compounds, Gd6Co2.2Al0.8 demonstrates largest magnetocaloric effect with magnetic entropy change of −10.89 J/kg⋅K at 75 K for a field change of 50 kOe (relative cooling power of ~760 J/kg).Neutron diffraction study indicates non-collinear abc-antiferromagnetic ordering of Tb6Co2.2Al0.8 in zero applied magnetic field. Below 63 K and down to 52 K, Tb6Co2.2Al0.8 exhibits antiferromagnetic ordering with magnetic space group I′22′2′ (wave vector K0 = [0, 0, 0]). Below 52 K and down to 1.5 K, the magnetic structure of Tb6Co2.2Al0.8 is sum of magnetic component with P21′212′ magnetic space group (wave vector K0 = [0, 0, 0]) and square-modulated antiferromagnetic component along c-axis of unit cell with K1 = [±1/4, 0, ±1/4] wave vector.

SYNTHESIS, PROPERTIES CaCu3Ti4O12 WITH COLOSSAL VALUE OF THE DIELECTRIC PERMITTIVITY

Ceramic materials CaCu3Ti4O12 were synthesized by solid-phase reactions technique. The sequence of chemical reactions during the synthesis has been determined. Phase CaCu3Ti4O12 appears at 700 °C. At 800 – 900 °C, the intermediate phases CaTiO3, CuTiO3 and Ca3Ti2O7 are formed. Calcium and copper titanates, CaTiO3 and CuTiO3 interact to form CaCu3Ti4O12. Ca3Ti2O7 phase with pyrochlore structure is stable and prevent the formation of final product, CaCu3Ti4O12. A method for the synthesis of CaCu3Ti4O12 by solid-state reactions technique from previously synthesized CaTiO3 (at 1050 °С) and CuTiO3 (at 950 °С), taken in a molar ratio of 1:3, is proposed. This method give the possibility to avoid the appearance of an undesirable Ca3Ti2O7 phase with the pyrochlore structure and to reduce the content of free copper oxide to value less than 0.5 mol.%. In addition, instead of the copper oxide, which is usually used in solid-state reaction technique, the chemically more active form of the copper-containing reagent, CuCO3∙Cu(OН)2 were used. This reduce the synthesis time of the intermediate CuTiO3. The crystal structure, chemical composition, microstructure and electrophysical parameters of ceramics have been analyzed. The synthesized ceramics CaCu3Ti4O12 is cubic body-centered (space group Im-3) with the unit cell parameter a = 7.3932 Å, which agreed with the literature data. The calculated tolerance factor of CaCu3Ti4O12, t = 0.7626 is not sufficient for a stabilization of peroskite ABO3 structure; that is why the crystal structure of this compound contains 3 different cation sites: dodecahedral (Ca2+), octahedral (Ti4+), tetrahedral (Cu2+). At 1150 °C, the density of CaCu3Ti4O12 ceramic sintered has a maximum (90% of the theoretical density). At infra-low frequencies (10-3 Hz), the dielectric constant (e) reaches record values of 107, however, dielectric losses (tg d) up to 10 were observed. In the frequency range 10-3 - 105 Hz the value of ɛ exceeds 104; and at 105 Hz minimum of the dielectric losses (tg δ ~ 0.1) is observed. A comparative analysis of methods for the synthesis of CaCu3Ti4O12 shows that the synthesis conditions of material of the same chemical composition can be crucial in creating high dense ceramic with uniform grains, high dielectric constant and low dielectric losses in a wide frequency range.

Thermoelectric properties of inverse perovskites A3TtO (A = Mg, Ca; Tt = Si, Ge): Computational and experimental investigations

Oxygen-containing inverse perovskites represent one possible solution to reduce the cost and enhance the sustainability of thermoelectric materials. Although oxygen-containing compounds may be thought to reduce the electronic mobility and thus the thermoelectric performance, computational studies on A3TtO (A = Mg, Ca; Tt = Si, Ge) revealed that they exhibit high electrical conductivity originating from Dirac cones at valence and conduction bands. High Seebeck coefficients were predicted arising from multiple degenerate bands, leading to enhanced power factors, and low thermal conductivities were predicted using the minimum thermal conductivity model. These predictions were validated by experimental studies on Ca3SiO and Ca3GeO, which were synthesized through high-temperature methods. They adopt an orthorhombic structure (space group Imma). Transport measurements show high Seebeck coefficients and low thermal conductivities for these compounds, confirming their potential for high thermoelectric performance.

Disorder–order phase transition in nanocrystalline titanium monoxide with two-sublattice ordering of structural vacancies

Atomic-vacancy ordering was achieved via prolonged annealing of nanocrystalline nonstoichiometric titanium monoxide TiOy possessing the average crystal size of ∼30 ± 10 nm in vacuo in the temperature range of 300–1200 K. The XRD and HRTEM data revealed the ordering based on the orthorhombic super-structures of M2X3 and M3X2 types (space group Immm), which are derived from the B1 structure of disordered cubic phase of γ-TiO.

Plutonium and Americium Aluminate Perovskites.

Both AmAlO3 and PuAlO3 perovskites have been synthesized and characterized using powder X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR), and 27Al magic angle spinning nuclear magnetic resonance spectroscopy (MAS NMR). AmAlO3 perovskite showed a rhombohedral configuration (space group R3̅c) in agreement with previous studies. The effect of americium α-decay on this material has been followed by XRD and 27Al MAS NMR analyses. In a first step, a progressive increase in the level of disorder in the crystalline phase was detected, associated with a significant crystallographic swelling of the material. In a second step, the crystalline AmAlO3 perovskite was progressively converted into amorphous AmAlO3, with a total amorphization occurring after 8 months and 2 × 1018 α-decays/g. For the first time, PuAlO3 perovskite was synthesized with an orthorhombic configuration (space group Imma), showing an interesting parallel to CeAlO3 and PrAlO3 lanthanide analogues. High-temperature XRD was performed and showed a Imma → R3̅c phase transition occurring between 473 and 573 K. The thermal behavior of R3̅c PuAlO3 was followed from 573 to 1273 K, and extrapolation of the data suggests that cubic plutonium perovskite should become stable at around 1850 K (R3̅c → Pm3̅m transition).