Crystal Structure Of La0 Research Articles

STRUCTURAL, MAGNETIC AND MAGNETOCALORIC PROPERTIES OF La0.7Sr0.2Ba0.1MnO3 MANGANITE

In this present work, the structural, magnetocaloric and magnetic properties of La0.7Sr0.2Ba0.1MnO3 (LSBM) manganite were investigated. The material was synthesized using the sol-gel method and X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM) devices were used to analyze structural properties such as crystal structure and surface morphology. XRD measurement revealed that the crystal structure of LSBM manganite is hexagonal. Based on the magnetic measurements, the TC value of La0.7Sr0.2Ba0.1MnO3 manganite compounds was calculated as 362 K. The ∆SM value of sample is established as 2.79 Jkg-1K-1 in an applied magnetic field of 5T. Arrott curves revealed that the phase transition was second order.

Structural and enhanced dielectric properties of Al-modified lanthanum strontium manganites

The crystal structure of La0.7Sr0.3Mn1−xAlxO3 (LSMAO) with x = 0,0.025,0.05,0.075 and 0.10 ceramics prepared by the Sol-gel method were investigated by employing the XRD technique. The XRD patterns analysis by employing the Rietveld analysis confirms the nonexistence of secondary crystal phase/s and, materials are crystallized to the R-3c(167) space group. The microstructural properties were studied using scanning electron microscope (SEM) and transmission electron microscope (TEM). The dielectric property, AC conductivity, complex impedance spectroscopy and complex electrical modulus have been studied over a wide range of frequencies (103 Hz–107 Hz) at different temperatures from 313K to 393K. The Non-Debye type relaxation process has been observed in synthesized samples confirmed from the Nyquist plot. The Cole-Cole plots were employed to estimate the individual grain and grain boundary contributions. The Maxwell-Wagner (MW) polarization model provides an explanation for the greater values of dielectric constant at the lower frequencies. The present study explores the technological usefulness of LSMAO.

Analysis Crystal Structure of La0.7Ba(1-xSrx)0.3MnO3 by Sol-Gel Method

Abstrak.Penelitian tentang struktur kristal bahan La0.7(Ba1-xSrx)MnO3 menggunakan metode sol-gel telah berhasil dilakukan. Bahan-bahan dasar yang digunakan dicampur di atas hot plate diaduk sambil ditetesi ammonia solution sehingga mencapai pH 7, selanjutnya didiamkan sampai diperoleh bentuk gel. Gel dikeringkan pada suhu 120°C, selanjutnya dilakukan pra-kalsinasi dengan suhu 650°C selama 6 jam, dilanjutkan dengan kalsinasi pada suhu 1000°C selama 12 jam, dan kemudian disinter pada temperatur 1200°C selama 12 jam. Hasil refinement data XRD memberikan informasi bahwa struktur kristal La0.7(Ba1-xSrx)MnO3 adalah rombohedral dengan space grup R-3c. Penambahan substitusi ion Sr2+ mengakibatkan terjadinya penurunan intensitas dan pergeseran puncak ke arah sudut yang lebih besar. Hal ini disebabkan karena pengaruh jari-jari ion Sr2+ yang lebih kecil dibandingkan dengan jari-jari ion Ba2+ . Abstract.In this research, La0.7(Ba1-xSrx)0.3MnO3 compound (x = 0; 0.2; 0.3; and 0.5) by sol-gel method has been investigated. The compound used is mixed on a hot plate until reached a pH 7 when dropped ammonia solution, then let stand until turn into a gel. Dehydrated gel at 120°C, pra-calcination at 650°C for 6 hours, calcination t 1000°C for 12 hours, and sintering at 1200°C for 12 hours. The result of refinement XRD pattern shown that samples are single phase with rhombohedral crystal structure with R-3c space group. The intensity decrease and peak list shift to larger angle when Sr-substitution increased, it’s caused ionic radii of Sr2+ is smaller than Ba2+ .

Enhanced high temperature microwave absorption of La0.9Sr0.1MnO3/MgAl2O4 composite ceramics based on controllable electrical conductivity

The high temperature microwave absorbing efficiency (HTMAE) of xLa0.9Sr0.1MnO3/(1 − x)MgAl2O4 composite ceramics was investigated by studying the crystal structure, electrical conductivity, and permittivity. The crystal structure of La0.9Sr0.1MnO3 and MgAl2O4 were maintained, but the Mn3+ and Al3+ ions were exchanged with each other through doping. The conductivity and permittivity of the composite ceramics increased with the increase of La0.9Sr0.1MnO3 content and test temperature. When x = 0.36, the electrical conductivity in La0.9Sr0.1MnO3 significantly enhanced the microwave polarization of the composite ceramics at high temperature. According to transmission/reflection modelling, the composite ceramics with x = 0.24 showed excellent HTMAE near the optimal thickness of 1.8 mm. Although the optimal thickness of the composite with x = 0.36 was reduced to 1.1 mm, the HTMAE was seriously lessened due to an impedance mismatch. xLa0.9Sr0.1MnO3/(1 − x)MgAl2O4 are promising as thin and efficient microwave absorbing materials at high temperatures and the microwave permittivity can be further enhanced by adjusting the conductivity of La0.9Sr0.1MnO3.

(Invited) Oxygen Evolution and Reduction on La0.5Sr0.5Co0.8Fe0.2O3- Δ Perovskites with Tunable Structural Features

Oxygen evolution (OER) and oxygen reduction (ORR) reactions are the fundamental processes occurring at the air electrode of metal-air batteries and fuel cells. Presently, large overpotentials are required for these reactions to occur at an appreciable rate. Therefore, development of catalysts capable of reducing the activation losses at the oxygen electrode is highly desirable. Perovskite oxides are one of the most interesting low-cost electrocatalysts for air electrodes, because they can adopt a wide variety of chemical compositions and crystal structures, thereby enabling correlative studies between the electrocatalytic activity and their electronic structure (1, 2). Recently, we reported a possible relation between the cell volume of La0.6Sr0.4Fe0.6Mn0.4O3-δ perovskites and their ORR activity and selectivity (2 e- vs ‘’2+2’’ e- pathway), with lower cell volumes corresponding to higher number of exchanged electrons (3). It was also reported by others that some structural features in the perovskite influence the activity of these mixed oxides for both ORR and OER (4-6). In this presentation, we will discuss our recent studies on the ORR and OER activity of a series of La0.5Sr0.5Co0.8Fe0.2O3- δ electrocatalysts prepared by solution combustion synthesis. The choice of diverse experimental conditions allowed us to tune oxygen deficiency, microstrain and other structural properties. As exemplified in Figure 1, for one of the investigated electrocatalysts, thermal annealing in argon reduces the bond angle between the oxygen atom and the two B-site metal cations, resulting in a higher electrocatalytic activity for both OER and ORR. In addition to structure–electrocatalytic activity correlations, we will complement our comparative studies with analytical scanning electron microscopy and spatially resolved elemental mapping of selected electrode surfaces subjected to accelerated stability tests. Figure 1. Crystal structures of La0.5Sr0.5Co0.8Fe0.2O3- δ prepared from solution combustion using citrate as fuel and thermal annealed in Ar (top right) and in Air (bottom left). Differences in the Co-O-Co bond angle are highlighted. Oxygen evolution (OER, top left) and oxygen reduction (ORR, bottom right) polarization curves recorded in 0.1 M KOH at 5 mVs-1 and 1600 rpm.

Influence of silver (Ag) doping on a crystal structure of La0.7Ag0.1Ca0.2MnO3 and La0.65Ag0.15Ca0.2MnO3 manganites synthesized by sol-gel method

Perovskite manganite material has been extensively investigated because it has many attractive properties. In this paper, crystal structure of La0.7Ag0.1Ca0.2MnO3 (LACMO1) and La0.65Ag0.15Ca0.2MnO3 (LACMO15) materials will be reported. LACMO1 and LACMO15 materials were synthesized by sol-gel method with sintering temperature 900°C for 24h. Structural properties of LACMO1 and LACMO15 materials were characterized using X-Ray Diffractometer (XRD). The characterized results show a crystal structure transition from orthorhombic (Pnma spacegroup) to rhombohedral ( space group) along with increasing the concentration of Ag doping. The crystal structure transition show there is a distortion of the material structure caused by Ag-doping. Increasing the concentration of Ag doping may affect the tolerance factor (t) that used to measure the degree of distortion of a perovskite.

Preparation and crystal structure of La0.7Ba0.1Sr0.2Mn0.9Cu0.1O3 perovskite: a comparison between sol-gel and solid state process

Polycrystalline sample of La0.7Ba0.1Sr0.2Mn0.9Cu0.1O3 was successfully synthesized using sol-gel and solid state method. Despite the various condition employed during the process to synthesize the samples, the crystal structure of both samples show that both samples have formed a single phase without any impurities. Furthermore, in accordance with the same value of Goldschmidt factor, both samples crystallize with the same hexagonal structure and space group. A slight difference appears in the more detailed aspect of crystal structure which are unit cell volume, Mn-O bond length, and Mn-O-Mn bond angle. The unit cell volume is 354.797 Å3 for solid state method and 352.747 Å3 for sol-gel method. The bond length and bond angle are 1.967 Å and 164.026° for solid state method and 1.957 Å and 166.738° for sol-gel method.

Effect of Sintering Temperatures on the Crystal Structures of La0.9Sr0.1Ga0.8Mg0.2O3−δ

The crystal structures of electrolyte materials of La0.9Sr0.1Ga0.8Mg0.2O3−δ (LSGM) for solid oxide fuel cells prepared by low- and high-temperature solid state reactions and laser rapid sintering are studied by structural refinements of XRD patterns. The results of structural refinements show that the three series of samples by low- and high-temperature solid state reactions and laser rapid sintering crystallized in different structures. They are identified to be cubic with space group Pm m 3 (denoted as C-LSGM), monoclinic with space group I2/a (denoted as M-LSGM) and orthorhombic with space group Imma (denoted as O-LSGM), respectively. To understand the effect of sintering temperatures on the crystal structures, the Gibbs free energies of three structures are calculated. It indicates that the cubic phase has the priority to form at relatively lower temperatures due to its lowest Gibbs energy while the formation of monoclinic and orthorhombic phases requires higher and highest sintering temperatures. This is in agreement with the experiment conditions of the preparation of the three series of samples.

Facile Synthesis, Magnetic and Electric Characterization of Mixed Valence La0.75K0.25AMnTiO6 (A = Sr and Ba) Perovskites.

A new series of mixed valence perovskites, La0.75K0.25AMnTiO6 (A = Sr and Ba) nanocubes, have been synthesized by a mild hydrothermal route. From powder X-ray diffraction (XRD) analysis, the crystal structure of La0.75K0.25AMnTiO6 was solved as the orthorhombic symmetry (space group Pbnm) with a random A-site or B-site arrangement. The phase purity of the products was confirmed by ICP, SEM, and EDS analyses, and the oxidation states of the B-site metal atoms were determined to be +4 for Ti and +3/+4 for Mn from XPS results. The soft ferromagnetic behavior is present in both samples. The Curie point TC has been detected as high as 309 K in La0.75K0.25SrMnTiO6 and 217 K in La0.75K0.25BaMnTiO6. A Griffiths phase can be observed at the high temperature region, which is related to the magnetic inhomogeneity induced by the existence of short-range ferromagnetic clusters. The resistivity measurements indicate that the semiconducting properties of the samples can be depicted better by variable range hopping (VRH) due to a diluted double-exchange interaction of Mn3+-O-Mn4+ with Ti4+ doping.

High pressure effects on the magnetic and crystal structure of La0.75Ba0.25CoO3

The crystal and magnetic structure of the La0.75Ba0.25CoO3 has been studied as a function of temperature and high pressure up to 8 GPa using neutron powder diffraction. The crystal structure of the compound at room temperature is considered to be single phase rhombohedral (space group R3−c), at T = 50 K the crystal structure is described by two-phase model assuming the coexistence of the orthorhombic (Imma) and rhombohedral (R3−c) phases. The magnetic structure is found to be ferromagnetic with Curie temperature about 200 K and magnetic moment 1.6 μB per Co ion. Applied external pressure strongly reduces magnetic moment, it decreases down to 0.7 μB/Co at pressure of 8 GPa. The drop of magnetic moment is associated with a pressure-driven spin state crossover of the cobalt ions from the intermediate spin state to the low spin state.

Magnetoelectric and magnetodielectric properties of LSMO–(BCT–BZT) composites

The present paper reports magnetoelectric and magnetodielectric properties of La0.67Sr0.33MnO3 and (Ba0.7Ca0.3TiO3)–(BaZr0.2Ti0.8O3) composites. y(La0.67Sr0.33MnO3) + (1 − y)[x(Ba0.7Ca0.3TiO3)–(1 − x)(BaZr0.2Ti0.8O3)] particulate composites are prepared for x = 0.40, 0.45, and 0.50 and for y = 0.1 and 0.175. Ferroelectric compositions [x(Ba0.7Ca0.3TiO3)–(1 − x)(BaZr0.2Ti0.8O3)] are synthesized via ceramic route, while La0.67Sr0.33MnO3 is synthesized via hydroxide co-precipitation route. Composites of La0.67Sr0.33MnO3 and (Ba0.7Ca0.3TiO3)–(BaZr0.2Ti0.8O3) are synthesized using ceramic method. The crystal structures of La0.67Sr0.33MnO3, [x(Ba0.7Ca0.3TiO3)–(1 − x)(BaZr0.2Ti0.8O3)], and composites are investigated using X-ray diffractograms, while microstructures are investigated using scanning electron microscope. The dielectric properties of [x(Ba0.7Ca0.3TiO3)–(1 − x)(BaZr0.2Ti0.8O3)] are determined as a function of temperature between 30 and 150 °C and at frequencies 1, 10, 100 kHz, and 1 MHz. The investigations on P–E hysteresis loops of [x(Ba0.7Ca0.3TiO3)–(1 − x)(BaZr0.2Ti0.8O3)] show useful values of maximum polarization (Pmax) and remanent polarization (Pr). Dielectric study on composites is carried out as a function of frequencies between 1 kHz and 1 MHz and for magnetic field between 0 and 6 KOe. The linear magnetoelectric coefficient “α” and quadratic magnetoelectric coefficient “β” are measured with the help of custom-designed setup. The results on magnetoelectric and magnetodielectric properties of composites are interesting.

Magnetic interactions in La0.7Sr0.3Mn1−xMexO3 (Me=Ga, Fe, Cr) manganites

Magnetic properties and crystal structure of La0.7Sr0.3Mn1−xMexO3 (Me=Ga, Fe, Cr; x≤0.3) have been studied by neutron powder diffraction and magnetization measurements. It is shown that substitution of manganese ions by chromium or gallium ions (x=0.3) leads to phase separation into antiferromagnetic and ferromagnetic phases whereas replacement by Fe ions stabilizes spin glass state (x=0.3). Ferromagnetic interactions in Cr-substituted compounds are much more pronounced than in Fe- and Ga-doped ones. Magnetic properties are discussed in the model assuming a dominance of superexchange interactions. It is considered that ferromagnetism in the Cr-substituted compositions is associated with nearly equal contributions from positive and negative components of the superexchange interaction between Mn3+ and Cr3+ ions as well as to mixed valence of chromium ions. The spin glass state observed for the Fe-doped sample (x=0.3) is associated with strong antiferromagnetic superexchange between Fe3+–O–Fe3+ and Fe3+–O–(Mn3+, Mn4+).

Suppression of the antiferromagnetic state in La0.82Ba0.18CoO3 cobaltite at high pressure

The crystal and magnetic structure of La0.82Ba0.18CoO3 complex cobalt oxide is studied by the neutron diffraction technique at high pressure (up to 4 GPa) within the temperature range of 10–290 K. At normal pressure, the crystal structure of La0.82Ba0.18CoO3 corresponds to the rhombohedral symmetry described by the space group R3c. At temperatures below T N = 100 K, the onset of a noncollinear antiferromagnetic (AFM) phase is observed. This phase is characterized by the wave vector k = (0, -0.5, 0.5). The applied high pressure leads to the rapid suppression of the AFM phase, which completely vanishes at P > 2 GPa. In La0.82Ba0.18CoO3, the degree of instability of the AFM phase with respect to the high pressure is appreciably higher than that in the related compounds with the ferromagnetic ground state. The correlation between the instability of the AFM state in La0.82Ba0.18CoO3 at high pressure and the changes in the electron configuration of Co3+ ions is also analyzed.

Structural, thermal and electrical conductivity characteristics of Ln0.5Sr0.5Ti0.5Mn0.5O3±d (Ln: La, Nd and Sm) complex perovskites as anode materials for solid oxide fuel cell

The Ti and Mn replaced complex perovskites, Ln0.5Sr0.5Ti0.5Mn0.5O3±d (Ln: La, Nd and Sm), were reported as potential anode materials for high temperature-operating solid oxide fuel cells (HT-SOFCs). For the present research study, synthesis, crystallographic, thermal and electrical conductivity properties of Ln0.5Sr0.5Ti0.5Mn0.5O3±d complex perovskites were investigated using X-ray diffraction (XRD), Rietveld method, thermogravimetric analysis (TGA) and electrical conductivity to apply these oxide materials for the HT-SOFC anode materials.XRD results showed that Ln0.5Sr0.5Ti0.5Mn0.5O3±d oxide systems synthesized as single phases did not react with 8mol% yttria stabilized zirconia (8YSZ) and 10mol% Gd-doped cerium oxide (CGO91) up to 1500°C and did not decompose under dry 3.9% hydrogen at 850°C. The crystal structures of La0.5Sr0.5Ti0.5Mn0.5O3±d (LSTM), Nd0.5Sr0.5Ti0.5Mn0.5O3±d (NSTM) and Sm0.5Sr0.5Ti0.5Mn0.5O3±d (SSTM) showed orthorhombic symmetry with the space group Pbnm and SSTM showed a more distorted structure. Thermogravimetric analysis (TGA) proved weight gains in these three sample occurred under oxidizing conditions and weight loss under reducing conditions. Electrical conductivity values of NSTM were higher than those of LSTM and SSTM under oxidizing and reducing conditions.

Enhanced green emission from La0.4F3:Ce0.45,Tb0.15/TiO2 core/shell structure

Nano sized La0.4F3:Ce0.45,Tb0.15 (core), La0.4F3:Ce0.45,Tb0.15 (TiO2) (core) shell, La0.55F:Ce0.45, and La0.85F3:Tb0.15 particles were synthesized by adopting co-precipitation technique in acidic environment and coated with TiO2 to form a core-shell structure by adopting a mechanical dispersion method at room temperature. The synthesized materials were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-Vis) absorption, photoluminescence and lifetime spectroscopy. The crystal structure of La0.4F3:Ce0.45,Tb0.15 remained the same as LaF3 after being doped with Ce and Tb ions but with a slight decrease in the lattice parameter. TEM image confirmed the formation of a core-shell structure. The La0.4F3:Ce0.45,Tb0.15/TiO2 exhibited Tb3+ fluorescence enhancement by a factor of 1.76. Scintillation from the synthesized materials was also observed under X-ray excitation.

Crystal structure and physicochemical properties of doped lanthanum manganites

Substituted lanthanum-strontium manganites La0.7Sr0.3Mn0.9Me0.1O3 ± δ (Me = Ti, Cr, Fe, and Cu) are obtained by standard ceramic and glycerin-nitrate techniques. High-temperature powder X-ray diffraction is employed to study the crystal structure of La0.7Sr0.3Mn0.9Me0.1O3 ± δ oxides. It is shown that in the range 298–1023 K in air, La0.7Sr0.3Mn0.9Me0.103 ± δ manganites crystallized in an orthorhombic cell (space group R-3c). The isobaric temperature dependences of unit cell parameters are determined. Thermal expansion coefficients are calculated for La0.7Sr0.3Mn0.9Me0.103 ± δ oxides. The conductivity of La0.7Sr0.3Mn0.9Me0.103 ± δ is studied as a function of temperature in the range 500 K ≤ T ≤ 1200 K in air. It is shown that substituting 3d metal for manganese considerably lowers the conductivity of basic La0.7Sr0.3Mn0.9O3 ± δ. The chemical stability of iron-substituted manganite La0.7Sr0.3Mn0.9Fe0.1O3 ± δ is studied with respect to the electrolyte material.

Magnetic Refrigeration Properties of ${\hbox{La}}_{0.8}\hbox{Ca}_{0.2}\hbox{Mn}_{0.99}{^{57}\hbox{Fe}_{0.01}}\hbox{O}_{3}$

The La0.8Ca0.2Mn0.99 57Fe0.01O3 sample was prepared by sol-gel method. The crystallographic and magnetic properties of La0.8Ca0.2Mn0.99 57Fe0.01O3 have been studied using X-ray diffraction (XRD), vibrating sample magnetometer (VSM) and Mossbauer spectroscopy measurements. The crystal structure of La0.8Ca0.2Mn0.99 57Fe0.01O3 was found to be orthorhombic (Pnma) structure with lattice constants ao=5.486 Aring, bo=7.761Aring, and co=5.510 Aring at room temperature. The Curie temperature (Tc) is determined to be 160 K by zero field cooled (ZFC) magnetization curve under 5 kOe applied field. The maximum value of magnetic entropy changes, |DeltaSM| is 1.25 J/kgldrK at 157 K under 13 kOe applied field. Mossbauer spectrum at 4.2 K was fitted with two independent magnetic components of the magnetic hyperfine fields Hf,1=526 kOe and Hf,2=501 kOe. Mossbauer spectra show that the two well-resolved sextets show nearly equal intensities between them without any external fields. This unusual phenomenon provides direct evidence of the two-phase character of the metallic state in the mixed valence state of La0.8Ca0.2Mn0.99 57Fe0.01O3 powder.

Structural investigation of anion-deficient manganites La0.7Sr0.3MnO3 − δ

The crystal structure of the anion-deficient manganites La0.7Sr0.3MnO3 − δ (δ = 0, 0.10, 0.15, 0.20) is investigated using high-resolution neutron diffraction. At room temperature, the crystal structure of the stoichiometric manganite La0.7Sr0.3MnO3 and the anion-deficient manganite La0.7Sr0.3MnO2.9 is satisfactorily described in rhombohedral space group R $$\bar 3$$ c. The anion-deficient manganite La0.7Sr0.3MnO2.85 is characterized by two perovskite phases with space groups R $$\bar 3$$ c and 14/mcm. The crystal structure of the La0.7Sr0.3MnO2.8 manganite corresponds to the structure of a perovskite phase with space group I4/mcm. It is established that the phase separation in the crystal structure of the La0.7Sr0.3MnO3 − δ manganites at a temperature of 293 K is associated with a nonuniform distribution of oxygen vacancies.

Oxygen-deficiency and high-pressure effects on the magnetic and crystal structures of La0.7Sr0.3MnO3−d managanites

The magnetic and crystal structures of anion-deficient La0.7Sr0.3MnO3−d manganites (d = 0.15 and 0.20) are studied by neutron diffraction in the range of high pressures 0–5 GPa and temperatures 10–300 K. It is found that a spin-glass state forms in La0.7Sr0.3MnO2.85 below Tg ∼ 50 K, while magnetic phase separation is observed in La0.7Sr0.3MnO2.80, which is characterized by the coexistence of AFM domains of the C type with spin-glass domains. As distinct from the stoichiometric A0.5Ba0.5MnO3 manganites (A = Nd, Sm), in which the high-pressure effect suppresses the spin-glass state and gives rise to ferromagnetism, the spin-glass state in La0.7Sr0.3MnO2.85 is stable under pressure. The bulk modulus of La0.7Sr0.3MnO2.85 is considerably smaller than that for the stoichiometric La0.7Sr0.3MnO3 compound. The causes of the formation of different types of the magnetic structure in La0.7Sr0.3MnO3−d (d = 0.15 and 0.20) and different high-pressure effects on the magnetic structure of stoichiometric and anion-deficient manganites are analyzed.

Concentration-dependent structural transition in the La0.70Sr0.30MnO3−δ system

The crystal structure of anion-deficient La0.70Sr0.30MnO3−δ manganites (δ = 0, 0.10, 0.15, and 0.20) has been studied by powder neutron diffraction at room temperature. The crystal structures of the stoichiometric La0.70Sr0.30MnO3 and anion-deficient La0.70Sr0.30MnO2.90 samples are satisfactorily described by the rhombohedral R $$\bar 3$$ c space group. The anion-deficient La0.70Sr0.30MnO2.85 sample separates into two perovskite phases with the R $$\bar 3$$ c and I4/mcm space groups. The crystal structure of La0.70Sr0.30MnO2.80 cannot be described by a single perovskite phase in the I4/mcm space group. It is found that the clustering of oxygen vacancies is the cause of structural phase separation at 293 K in anion-deficient La0.70Sr0.30MnO3−δ manganites.