Formation Of Perovskite Phase Research Articles

A Study on Synthesis and Characterization of Dy-Doped La0.6Sr0.4Co0.2Fe0.8O3−δ via the Coprecipitation Method

The perovskite Lanthanum Strontium Cobalt Ferrite (LSCF) is investigated as the cathode material used in intermediate-temperature solid oxide fuel cells (IT-SOFCs). In the present study, La0.6−xDyxSr0.4Co0.2Fe0.8O3−δ (x = 0, 0.3, 0.6) was synthesized through the coprecipitation method. The obtained precipitate was calcined at 500, 700, 900, and 1000°С. Phase characterization of the synthesized LSCF and LDySCF powder before and after heat treatment at 700°С was carried out by X-ray diffraction (XRD) analysis. XRD patterns revealed that the perovskite phase was obtained at 700°С in all calcined samples. Chemical bond study to investigate the synthesis process was conducted using the Fourier transform infrared spectroscopy technique. Thermal analysis of DTA and TG has been utilized to investigate how the calcination temperature affects the perovskite phase formation. According to the STA results, the perovskite phase formation started at 551°С and completed at 700°С. The density values of synthesized powders were 6.10, 6.11, and 6.37 g·cm−3for the undoped and doped samples calcined at 700°С. Powder morphology was studied by field emission scanning electron microscopy (FE-SEM). The micrographs showed the spherical-shaped particles with the average particle size of 24–131 nm.

Improved ferroelectric properties and softening effect in BLTF ceramics

A comparative study is reported on the ferroelectric ceramics with compostional formula Ba0·98La0·02Ti0·98Fe0·02O3 (BLTF1) and Ba0·97La0·02Ti0·98Fe0·02O3 (BLTF2; valency compensated). The samples were prepared by solid state route and sintered in air at 1325 °C for 4 h. The X-ray diffraction analysis confirmed the formation of tetragonal perovskite phase. The prepared samples were characterized for their dielectric and ferroelectric properties at different temperatures at 1, 5, 10 and 100 kHz. Enhancement in ferroelectric properties (Pr = 11.25 μC/cm2, Ec = 9.05 kV/cm) was observed in BLTF2 ceramics as compared to BLTF1 ceramics (Pr = 6.53 μC/cm2, Ec = 9.35 kV/cm) along with the observation of electrocaloric effect. The value of piezoelectric coefficient ‘d33’ was found to be 140 pC/N and 163 pC/N for BLTF1 and BLTF2 samples respectively. The present investigations show that the valency compensation method can improve the ferroelectric properties of the ferroelectric ceramics thereby making them more suitable for different applications.

Influence of accessory phases and surrogate type on accelerated leaching of zirconolite wasteforms

A fraction of the UK Pu inventory may be immobilised in a zirconolite ceramic matrix prior to disposal. Two zirconolite compositions, targeting CaZr0.80Ce0.20Ti2O7 and CaZr0.80U0.20Ti2O7, were fabricated by hot isostatic pressing, alongside a reformulated composition, nominally Ca0.80Zr0.90Ce0.30Ti1.60Al0.40O7, with an excess of Ti and Zr added to preclude the formation of an accessory perovskite phase. Materials were subjected to accelerated leaching in a variety of acidic and alkaline media at 90 °C, over a cumulative period of 14 d. The greatest Ce release was measured from CaZr0.80Ce0.20Ti2.00O7 exposed to 1 M H2SO4, for which 14.7 ± 0.2% of the original Ce inventory was released from the wasteform into solution. The extent of Ce leaching into the solution was correlated with the quantity of perovskite present in the wasteform, and associated with the incorporation and preferential dissolution of Ce3+. CaZr0.80U0.20Ti2.00O7 exhibited improved leach resistance relative to CaZr0.80Ce0.20Ti2.00O7, attributed to the decreased proportion of accessory perovskite, with 7.1 ± 0.1% U released to in 8 M HNO3 after 7 d. The Ca0.80Zr0.90Ce0.30Ti1.60Al0.40O7 composition, with no accessory perovskite phase, presented significantly improved leaching characteristics, with < 0.4%Ce released in both 8 M HNO3 and 1 M H2SO4. These data demonstrate the need for careful compositional design for zirconolite wasteforms with regard to accessory phase formation and surrogate choice.

The miscibility of calcium silicate perovskite and bridgmanite: A single perovskite solid solution in hot, iron-rich regions

Calcium silicate perovskite and bridgmanite are two phases believed to coexist throughout the lower mantle, which at some temperature, at least theoretically, dissolve into each other to form a single perovskite solid solution (CaxMg1−xSiO3). This may have large seismic and geochemical implications due to the changes in density, elasticity and element partition coefficients between single and mixed phase perovskites. DFT Molecular Dynamics has been used to estimate the miscibility of bridgmanite and calcium perovskite at pressures between 25 and 125 GPa. At 125 GPa (where mixing is the greatest in our pressure range) to mix 1% of Ca-pv into bridgmanite requires a temperature of 2042 K, 5% 2588 K, 10% 2675 K and 50% 2743 K. Therefore, in a simplified lower mantle chemistry an extensive MgSiO3–CaSiO3 solid solution is not expected to occur. However, a simple model was employed to test whether the presence of other elements might influence this mutual solid solution and it was demonstrated that if sufficient concentrations (>1 at.%) of additional elements are present then miscibility may become favourable. Of the elements likely to be present at these concentrations it appears that ferrous iron promotes, whilst aluminium inhibits, a single-phase perovskite solid solution. To a lesser extent ferric iron may both increase and decrease perovskite miscibility. Modelling for realistic mantle compositions suggests that basaltic lithologies will always retain two perovskite components, whereas a single perovskite solid solution may be preferred in hot and/or iron-rich pyrolytic bulk compositions near the base of the lower mantle. Static calculations indicate perovskite miscibility may cause pyrolytic lithologies (with 12.5% CaSiO3) to possess lower density (−0.14–0.25%), Vs (−1.5–3.5%) and Vp (−0.5–1.2%), and higher VΦ (+ 0.00–0.75%) than predicted for assemblages containing two perovskites. These seismic changes, while preliminary, are similar to those observed in the LLSVPs which are also regions that are likely hotter than the surrounding mantle and thus possess conditions promoting the formation of a single perovskite phase.

Influence of Compacting Pressure on the Dielectric Properties of La-modified Bismuth Ferrite Multiferroics Prepared by Rapid Liquid-phase Sintering Method

Structure, perovskite phase formation, chemical and phase composition, microstructure, morphology and dielectric properties of the single-phase lanthanum-modified bismuth ferrite multiferroic ceramics obtained by the rapid liquid-phase sintering method under different compacting pressures have been investigated using X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, thermogravimetry/differential thermal analysis and dielectric spectroscopy methods. The temperature and time for an express preparation of the single-phase Bi0.9La0.1FeO3 ceramics with formation of a perovskite structure have been found out. With an increase in the compacting pressure P from 100 to 1100 MPa, the dielectric constant ε′ changes by ∼25% and ∼80% in the low-frequency and ultra-high frequency ranges, respectively. In the low-frequency range, all samples depending on the pressure P demonstrate excellent dielectric behavior with a stable dielectric constant and quite low dielectric loss that make these samples perspective for their possible practical application in microelectronic and spintronic.

Rietveld Study of the Changes of Phase Composition, Crystal Structure, and Morphology of BiFeO3 by Partial Substitution of Bismuth with Rare-Earth Ions

BiFeO3 is an interesting material due to its multiferroic properties. It attracts attention due to its potential applications in spintronics and in microelectronics for data storage, among others. Single-phase bulk material from BiFeO3 is difficult to synthesize. The kinetics of perovskite phase formation most often leads to the presence of impurity phases. It has been shown that low levels of replacement of Bi with rare earth ions lead to stabilization of the perovskite phase. In the present work, Rietveld refinement of the crystal structure based on powder X-ray diffraction patterns was applied to study the influence of partial substitution of Bi by rare-earth (RE) elements with different ionic radii on structural and morphological properties of the ferrite phase. Substitution by large RE ions was found to preserve the rhombohedral symmetry of BiFeO3, whereas substitution by smaller RE ions led to the coexistence of two polymorphic perovskite phases with rhombohedral R3c and orthorhombic Pnma symmetries. The unit cell parameters as well as the interatomic distances and angles, not only around the A cation but also around the iron ions, were influenced by the substitution. The mean crystallite and particle size decreased with the decrease of ionic radius of substituting RE ion.

A study of enhanced structural, microstructural and dielectric behaviour of aliovalent ions doped BaZr0.05Ti0.95O3 ceramic

The lead-free ceramics are considered to be the best substitutes for lead based ceramics which have tremendous harmful effects regarding environmental pollution. In this concern, the lead-free ceramics have been widely attracted by research communities. In the present study we have prepared lead free BaZr0.05Ti0.95O3perovskite ceramics with various doping concentrations of Gd3+ ions by the conventional solid-state reaction method. The perovskite phase formation was studied by x-ray diffraction which indicate the transformation of crystal symmetry from orthorhombic to tetragonal structure for the Gd3+ ions doped samples. The scanning electron microscopy studies revealed the modification in grain size on doping Gd ions also the energy dispersive X-ray spectra have been obtained to study the compositional variations. The dielectric and loss studies have been performed in the large range of temperature and frequency. The low dielectric loss and high dielectric constant suggests possible applications in memory devices and ceramic capacitors. Temperature coefficient of capacitance plots have also been plotted.

Processing of Y3+-doped Ba(Ce,Zr)O3 by using the sol–gel method assisted with functionalized activated carbon as a composite anode for proton ceramic fuel cells

A functionalized activated carbon derived from palm oil empty fruit bunches is utilized as a dispersing agent to synthesize BaCe0.54Zr0.36Y0.1O2.95 (BCZY) powder, which is used as a composite anode. The characteristics of pristine and modified powders are presented and compared. The Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) results confirm the elimination of the intermediate compounds in both powders, thereby promoting single perovskite phase formation. The field emission scanning electron microscopy (FESEM) image demonstrates that the modified powder has a smaller particle size and less agglomeration than the pristine powder. The modified powder's performance in the composite anode of the anode-supported single cell shows lower ohmic and polarization resistances than pristine powder. The improved electrochemical performance of nickel oxide mixed with modified powder indicates the importance of tailoring the pristine powder microstructure as a composite anode for proton ceramic fuel cells.

Enhancement of structural, magnetic, dielectric, and transport properties of Nb substituted 0.7BiFeO3-0.3BaTiO3 solid solution

The present study reports the structural, magnetic, dielectric, transport, and electronic properties of Nb substitution in the multiferroic (0.7- x )BiFeO 3 -0.3BaTiO 3 - x Nb 2 O 5 solid solution. Rietveld refined x-ray diffraction results confirm the perovskite phase formation along with a transformation in the structural symmetry, which exhibit a monotonous enhancement in the unit cell parameter with Nb substitution and a monotonous increase in the lattice parameters is observed with increased Nb concentration. Subsequently, scanning electron micrographs and Raman spectroscopy substantiates these structural changes. Interestingly, magnetic ordering temperature and net magnetization enhanced remarkably for the Nb substituted samples and a maximum value of saturation magnetization (1.95 emu/g) is accomplished for x = 0.10, which is significantly higher as compared with 0.11 emu/g for the parent compound ( x = 0). A large value of remanence magnetization (0.8 emu/g) for the highest Nb-dopant ( x = 0.10) is obtained as compared to other transition metal-doped BF-BT systems, which make it very useful in memory device applications. Two dielectric anomalies within the temperature ranges of 200 ≤ T ≤ 400 °C and 400 ≤ T ≤ 500 °C appear due to Nb substitution in the BF-BT phase. The phenomenon of dielectric relaxation with a larger dielectric constant was observed near the Curie temperature. Temperature-dependent dielectric and magnetic study confirm the coupling between electric and magnetic dipoles in all Nb substituted samples. Impedance spectroscopy results within the frequency (100 Hz ≤ υ ≤ 1 MHz) confirm Debye-type behavior and maximum bulk resistance of ~110 kΩ for x = 0.10. Conductivity data follow Jonscher's power law and confirms that the conduction phenomenon is dominated by the mechanism of charge carriers hopping. Arrhenius model estimate the values of activation energies for x = 0, 0.03, 0.05, and 0.10 samples to be 0.61, 1.12, 1.08, and 1.22 eV, respectively. Room temperature x-ray photoemission spectroscopy measurements for the constituent Bi, Ba, Ti, and Nb elements exhibit that they exist in their 3+, 2+, 4+, and 5+ valence states, respectively, which do not alter with the increased Nb substitution. The core-level spectra of Fe 2 p manifest a complex multiplet structure and confirms its trivalent state in the samples. • A monotonous increase in the lattice parameters with Nb substitution. • Significant enhancement in the net magnetization and effective magnetic moment with Nb. • The dielectric and magnetic study affirm coupling between electric and magnetic dipoles. • Impedance spectroscopy manifests a Debye-type behavior. • The conduction phenomenon is dominated by the mechanism of charge carriers hopping.

20.8% Slot‐Die Coated MAPbI3 Perovskite Solar Cells by Optimal DMSO‐Content and Age of 2‐ME Based Precursor Inks

AbstractSolar cells incorporating metal‐halide perovskite (MHP) semiconductors are continuing to break efficiency records for solution‐processed solar cell devices. Scaling MHP‐based devices to larger area prototypes requires the development and optimization of scalable process technology and ink formulations that enable reproducible coating results. It is demonstrated that the power conversion efficiency (PCE) of small‐area methylammonium lead iodide (MAPbI3) devices, slot‐die coated from a 2‐methoxy‐ethanol (2‐ME) based ink with dimethyl‐sulfoxide (DMSO) used as an additive depends on the amount of DMSO and age of the ink formulation. When adding 12 mol% of DMSO, small‐area devices of high performance (20.8%) are achieved. The effect of DMSO content and age on the thin film morphology and device performance through in situ X‐ray diffraction and small‐angle X‐ray scattering experiments is rationalized. Adding a limited amount of DMSO prevents the formation of a crystalline intermediate phase related to MAPbI3 and 2‐ME (MAPbI3‐2‐ME) and induces the formation of the MAPbI3 perovskite phase. Higher DMSO content leads to the precipitation of the (DMSO)2MA2Pb3I8 intermediate phase that negatively affects the thin‐film morphology. These results demonstrate that rational insights into the ink composition and process control are critical to enable reproducible large‐scale manufacturing of MHP‐based devices for commercial applications.

Spontaneous Ion Migration via Mechanochemical Ultrasonication in Mixed Halide Perovskite Phase Formation: Experimental and Theoretical Insights.

We present a simple yet powerful synthesis process to prepare compound-phase perovskite nanoparticles (MAPbX3-nYn; MA = CH3NH3+ and X/Y = I, Br, or Cl). This is achieved by mixing two pure-phase perovskites (MAPbX3 and MAPbY3) by using ultrasonic vibration as a mechanochemical excitation. Unlike conventional methods, this procedure does not require any effort in designing a reaction or choosing any particular precursor. X-ray diffraction and TEM studies confirm compound-phase formation in all possible stoichiometries. The origin behind ultrasonic mixing lies in the generation of mechanical stress and high temperature arising from acoustic cavitation during reaction. Long-term experimental stability of the compound-phase is comprehended theoretically by simulating the temperature-dependent Gibbs free energy. Negative mixing entropy plays a crucial role during the synthesis which leads to better stabilization of the compound-phase perovskite over the pure-phase. The ease of synthesis and remarkable phase stability make this process effective and less cumbersome for perovskite nanoparticle synthesis.

Retaining graphene structure in the synthesis of its composite with BiFeO3

Introduction of graphene in the Bi 2 O 3 -Fe 2 O 3 system has been found to facilitate the formation of perovskite phase of BiFeO 3 (BFO). The room temperature XRD pattern shows that the formation of BiFeO 3 (BFO) and also its composite with graphene has started at a sintering temperature as early as 300 0 C. Both XRD and FESEM of the sintered sample has shown that the addition of graphene has a marked effect on both the structure and microstructure of BiFeO 3 (BFO). Micro Raman spectra shows intensity ratio of 2D to G is around 1 indicating the presence of graphene as bi-layer in composite even upto a sintering temperature of 600 0 C. The graphene flaky nature with stacking of layers and sheet like folds having randomly orientation morphology has been confirmed from the TEM of the composite. So, an enhanced multiferroic properties has been envisioned due to the presence of π conjugate carbon network in the BFO matrix.

Controlling the Formation Process of Methylammonium-Free Halide Perovskite Films for a Homogeneous Incorporation of Alkali Metal Cations Beneficial to Solar Cell Performances

Incorporating multiple cations of the Ia alkali metal column of the periodic table (K+/Rb+/Cs+) to prepare m-AMCs perovskite film is promising for boosting the photovoltaic properties. However, contrary to K+, both Cs+ and Rb+ suffer from non-uniformity at the origin of performance and stability losses. In this paper, Ammonium chloride (NH4Cl) additive is shown to address this concern. We analyze step-by-step the effects of NH4Cl Additive and Alkali Metal Cations (K+/Rb+/Cs+) on the one-step film formation process of methylammonium-free, formamidinium-based, halide perovskites. First, we highlight the action of NH4Cl additive on the spin-coating and the anti-solvent dripping processes. We show that it improves the solubility of PbI2 in solution by forming an intermediate and then favor the perovskite phase formation. Then, we investigate the annealing process by introducing depth profile evolution monitoring by the glow discharge optical emission spectroscopy (GD-OES) technique. The real-time distribution changes of m-AMCs in the film upon annealing at 155°C is visualized. We show that K at low concentration is homogeneously distributed throughout the film. Cs is more concentrated at the surface and Rb in the film depth. With NH4Cl additive, these two alkali metals are more homogeneously distributed. We show that NH4Cl can slow down the movement of m-AMCs so that they are better evenly distributed into the perovskite layer. Moreover, it changes the growth direction of the perovskite film changes, making the overall crystallization quality improved and the distribution more uniform. It results in perovskite films with large monolithic grains, permitting a high stabilized power conversion efficiency (PCE) over 21%. Finally, by combining AC additive and film surface treatment with n-propylammonium iodide (PAI), the performance was further upgraded at a stabilized PCE of 22.04%.

The Formation of Perovskite during the Combustion of an Energy-Rich Glycine-Nitrate Precursor.

The effect of different regimes of combustion of glycine–nitrate precursors on the formation of perovskite phases (LaMnO3 and LaCrO3) without additional heat treatment was studied. The following three combustion regimes were compared: the traditional solution combustion synthesis (SCS), volume combustion synthesis (VCS) using a powdered precursor, and self-propagating high-temperature synthesis (SHS) using a precursor pellet. The products of combustion were studied using a series of physicochemical methods (attenuated total reflection infrared spectroscopy (ATR FTIR), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and thermal analysis). SHS was found to be the most productive regime for the formation of perovskite because of its ability to develop high temperatures in the reaction zone, which led to a reduced content of the thermally stable lanthanum carbonate impurities and to an increased yield and crystallite size of the perovskite phase. The reasons for the better crystallinity and purity of LaCrO3 as compared with LaMnO3 is also discussed, namely the low temperatures of the onset of the thermolysis, the fast rate of combustion, and the favorable thermodynamics for the achievement of high temperatures in the reaction zone.

Unraveling the Impact of Halide Mixing on Crystallization and Phase Evolution in CsPbX3 Perovskite Solar Cells

Summary All-inorganic perovskite solar cells (PSCs) have attracted wide attention for their excellent thermal stability. However, the detailed crystallization process and complicated phase-transition mechanism of the CsPbX3 film with different halide compositions (I, Br, Cl) remain mysterious. In this study, systematic investigations are performed via state-of-art in situ grazing-incidence wide-angle X-ray scattering to understand the role of the halide elements in all-inorganic perovskite crystallization kinetics, phase-transition, and stabilization mechanism as well as how film morphology and grain size are affected. Based on these results, we were able to fabricate high-performance ternary halide (I, Br, Cl) all-inorganic PSCs through a precise compositional engineering. Our results provide guidance for an in-depth understanding of all-inorganic perovskite materials and pave the way to obtain high-performance all-inorganic PSCs.

Electric properties of Mn-substituted Na0.5Bi0.5TiO3 ceramics in unpoled and poled states

ABSTRACT The Mn-substituted NBT ceramics were prepared by the conventional ceramic fabrication technique. X-ray diffraction (XRD) studies indicated the formation of perovskite phase with rhombohedral symmetry and with small amount of second phase. It was found that 0.5mol% and 0.1mol% dopant concentration enhances piezoelectric coefficients of d33 and k33, increases the depolarization temperature Td and decreases the dielectric loss. Dielectric study showed the existence of a diffuse phase transition at Tm ≈ 320°C. It was shown that a prior electric field poling process changes the character of ϵ(T) and tanδ(T) functions, as well as shifts of Td and Tm to higher temperature. The effects are mainly caused by the reinforcement of polarization/domain ordering and by the change of content rhombohedral/tetragonal phases by electric field action. The results were discussed in terms of lattice distortion and change of defect concentration.

Phase evolution and microstructure of BaBi2Nb2O9 ferroelectric ceramics

In the present study, the phase evolution of BaBi2Nb2O9 (BBN) composition prepared by solid-state reaction method have been studied. The detailed study for the formation of pure perovskite phase has been performed at a wide calcination temperature in the range of 700 °C–950 °C followed by sintering the ceramic at 1050 °C. The presence of a secondary phase is identified along with the formation of the desired BaBi2Nb2O9 phase and is found to decrease with increasing calcination temperature. High resolution (HRXRD) depicts the evolution of single-phase BaBi2Nb2O9 ceramic with an orthorhombic unit cell associated with the Fmmm space group at 950 °C, while SEM microstructural studies revealed the formation of dense plate-like grains on sintering the ceramic at 1050 °C. The optimum calcination temperature and sintering temperature were successfully investigated without any impurity traces for the application of high-temperature piezoelectricity and sensors.

Structural, ferroelectric, magnetic and magnetoelectric properties of (1-x) Ba0.85Ca0.15Zr0.1Ti0.9O3 -x La0.67Sr0.33MnO3 lead-free magnetoelectric composites

The influence of an additional La0.67Sr0.33MnO3 (LSMO) magnetic phase on the structural, ferromagnetic, ferroelectric, and magnetoelectric properties of Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) ferroelectric phase was studied for composites of (1-x)BCZT -xLSMO (x = 0, 25, 50, 75 and 100%). The ferroelectric BCZT sample showed a perovskite single phase formation with a tetragonal crystal structure of the P4mm space group, and the magnetic phase of LSMO presented a rhombohedral crystal structure of R3c space group as shown by XRD. The composite sample with 25% LSMO exhibited large ferroelectric and piezoelectric properties with remnant, saturation polarization, and coercive electric field Pr ~7.74 μC/cm2, Ps ~11.69 μC/cm2 and EC ~12.22 kV/cm with a piezoelectric coefficient d33 ~ 231 pC/N. The magnetic characterization for the composites showed that the sample containing 75% of LSMO revealed the highest remnant, saturation magnetization, and coercive field of Mr ~1.358 emu/g, Ms ~19.17 emu/g, and HC ~33.19 Oe, respectively. Moreover, it revealed the largest magnetoelectric coupling coefficient αME ~2.51 mV/cm.Oe with high coupling quality at a lower applied magnetic field. The results highlight the value of these composites as lead-free room temperature magnetoelectric sensors and actuators.

Synthesis, structural and optical properties of LaFe1-xCrxO3 nanoparticles

In this paper the structural, microstructural, and optical properties of solid solutions LaFe1-xCrxO3 (with x = 0, 0.25, 0.5, 0.75, 1) were examined. The samples were elaborated via the sol–gel process. X-ray diffraction (XRD) spectra prove the formation of perovskite phase in orthorhombic structure. From UV–visible measurements, absorption coefficient, band gap (Eg) energy, Urbach energy (EU), dielectric coefficient, refractive index (n), and optical conductivity were estimated and correlated to the Cr-content. Optical absorption measurements elucidate a direct band gap in solid solutions LaFe1-xCrxO3 (LFCO-x). The Eg energy get its minimum value of 1.82 eV at x = 0.5, as a semiconductor with relatively small band gap leading to promising materials for photonic applications. Additionally, we have investigated the effect of Cr substitution on some nonlinear optical parameters of LaFeO3. The obtained results show that the compound with x = 0.5 exhibits the enhanced nonlinear behavior.

Formation of Perovskite and Pyrochlore Phases during Mechanochemical Synthesis of Lead Ferroniobate

We have studied the effect of mechanical activation in lead ferroniobate synthesis on the formation of perovskite and pyrochlore phases during both mechanochemical synthesis and subsequent firing. It has been shown that, during mechanical activation, the first to form is the perovskite structure. During subsequent sintering of the material, the pyrochlore structure begins to form as well. As the firing temperature is raised to 650–750°C, the perovskite structure is again formed. We provide explanation for this process.