Structural and magnetic properties of LaCrO3 half

Ceramics International 42 (2016) 14499–14504

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Ceramics International journal homepage: www.elsevier.com/locate/ceramint

Structural and magnetic properties of LaCrO3 half-doped with Al Romualdo S. Silva Jr.a, Petrucio Barrozo a,n, N.O. Moreno a, J. Albino Aguiar b a b

Departamento de Física, Universidade Federal de Sergipe, Rod. Marechal Rondon, s/n, 49100-000, São Cristóvão, SE, Brazil Departamento de Física, Universidade Federal de Pernambuco, Aníbal Fernandes, s/n, 50740-560 Recife, PE, Brazil

art ic l e i nf o

a b s t r a c t

Article history: Received 15 April 2016 Received in revised form 7 June 2016 Accepted 9 June 2016 Available online 14 June 2016

Structural and magnetic properties of LaCrO3 half-doped with Al are reported in this work. Pure and halfdoped samples were prepared by combustion synthesis using urea as fuel. The crystal structure was investigated by X-ray diffraction and Rietveld analysis. A structural phase transition caused by a decrease of the chemical pressure was observed. The scanning electron microscopy (SEM) images show the formation of porous samples with particles of irregular morphologies. A quantitative Energy-dispersive X-ray spectroscopy (EDS) analysis on the surface indicates the inclusion of the Al on the structure. However, a small deficiency of La and Al was observed. Magnetization measurements as a function of temperature reveal an antiferromagnetic order in both samples. A large decrease of TN (Néel temperature) and a reduction of the frustration factor is observed in the sample doped with Al. The magnetic isothermal at 5 K shows a typical antiferromagnetic behavior with a slightly spin canting for the doped sample. & 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

Keywords: Combustion synthesis Structural transition Rietveld analysis Perovskite LaCrO3 LaAlO3

1. Introduction The study of the substitution and doping on the perovskite compound has brought significant advances in the understanding of physical properties and technological application of this material [1]. For example, it's known that the structural, electrical and magnetic properties of these compounds are strongly dependent on the level and type of the doping [2]. Recently, some studies have led to an improvement of multiferroic properties [3–7] and a better understanding of metal-insulator transition [8,9] in this material, as well as an increase storage capacity of magnetic hard disk drives [10–12] and magnetic sensors [13]. At room temperature, LaAlO3 crystallizes in a rhombohedral structure. A structural phase transition from rhombohedral to the ideal cubic perovskite structure takes place at 813 K [14,15]. This phase transition is pressure dependent and is accompanied by the rotations of the adjacent AlO6 octahedral about the [111] direction and relative compression of the LaO12 polyhedron [16]. LaAlO3 has been pointed as promising for substitute SiO2 as high-K gate dielectric due to its many advantages, such as good dielectric properties with high relative permittivity and low-temperature dependence of the resonant frequency [17]. This compound is widely used as substrate for growing thin films and it is a promising material to prepare substrates for the development of the high-speed devices [18]. Recently, it was shown that interface n

Corresponding author. E-mail address: [email protected] (P. Barrozo).

http://dx.doi.org/10.1016/j.ceramint.2016.06.059 0272-8842/& 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

phenomena between two insulate layers LaAlO3/SrTiO3 can result in the formation of a two-dimensional gas of electrons [19], and also to superconductivity [20] and ferromagnetism [21]. The mechanisms responsible for these properties are still under research. LaCrO3 compound has been extensively studied in the last years due to its high chemical stability and good electrical properties at high temperature, this enables it for use as interconnects for solid oxide fuel cell (SOFC's) [22,23]. LaCrO3 undergoes a structural phase transition at 540 K from orthorhombic to rhombohedral system [24]. By extrapolation c /a ratio obtained by X-ray diffraction and differential thermal analysis (DTA) data Geller and Raccah [25] suggested that LaCrO3 can present a cubic structure for temperatures above 1900 K. This compound presents a G-type antiferromagnetic order (AFM) below 290 K and is a p-type semiconductor with activation energy of 0.19 eV [26]. The Néel temperature of LaCrO3 increases with the applied pressure in accordance with the Bloch phenomenological rule [27]. The increase of the TN is accompained by a linear reduction of the structural phase transition temperature and of the magnetic moment [28]. When LaCrO3 is half-doped with Mn is observed a reduction of the magnetic transition temperature, an increase of the magnetic moment and a change of the electrical conduction mechanism close to room temperature [26]. In this work we describe a new preparation route for pure, and half-doped with Al, LaCrO3, by the combustion method. The effect of the chemical pressure, induced by partial substitution of the Cr3 þ (RCr3 þ ¼0.615 Å) by Al3 þ (RAl3 þ ¼0.535 Å), on the structural and magnetic properties in samples obtained at high temperatures after heat treatment is also investigated.

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R.S. Silva Jr. et al. / Ceramics International 42 (2016) 14499–14504

2. Material and methods LaCrO3 and LaCr0.5Al0.5O3 samples were prepared by the combustion method. The combustion method is based on the generation of a highly exothermic and self-sustaining reaction. The reaction was done in an open-air reactor using a stoichiometric mixture of reactants and urea (CH4N2O) as fuel. The cation precursor reagents used in this synthesis were La, Al and Cr nitrates. The amount of fuel was calculated by the elemental stoichiometric coefficient ϕe which reflects the relationship between the total valence of the “fuel” and “oxidizer” as described by S. R. Jain et al. [29]. ϕe ¼ 1 was considered for stoichiometrically balanced reactions. The total valence of the reactants and of the fuel was calculated considering that nitrogen has zero valence. The total molar ratio was 1:1:6 (La:Cr:Urea) for LaCrO3 and 1:0.5:0.5:6.0 (La: Cr:Al:Urea) for LaCr0.5Al0.5O3. The reactants were diluted in a small amount of deionized water. The solution was heated up to 100 °C to evaporate the water excess and form a gel. The temperature was then increased up to 300 °C where the ignition took place and a self-propagating reaction occurred, resulting in a fine powder with a doping dependent color (see inset of Fig. 1). The powder was then calcined at 500 °C for 12 h to burn the organics residues, followed by a new heat treatment at 1300 °C for 12 h.

Fig. 1. Experimental (Black cross), calculated (Red line) and difference (Blue dot) curves from the Rietveld refinement for samples calcined at 1300 °C for 12 h using Co-kα radiation: LaCrO3 (a) and LaAl0.5Cr0.5O3 (b). The inset in (a) and (b) shows a photograph of the powder after calcination at 500 °C for 12 h. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Powder X-ray diffraction (XRD) data were obtained at room temperature with a Rigaku diffractometer DMAX100 using Cu-Kα radiation tube operated at 40 kV and 40 mA. XRD data were taken in a step scan mode in the range of 20–80° (2θ) with step sizes of 0.02° and a scan speed of 0.02°/min. The structural parameters were extracted by using Rietveld refinement of the diffraction patterns using the General Structure Analysis System (GSAS) software. The Bragg peaks were modeled with the pseudo-Voigt function, and the background was estimated using a shifted Chebyshev function with interpolation between selected background points. The morphology, microstructure and particle size of LaCrO3 and LaCr0.5Al0.5O3 were examined by scanning electron microscopy (SEM) using JEOL microscope model JSN-5900 with an accelerating voltage of 15.0 kV, work distance of 10 mm and amplification of 25.000 times. The samples were covered with a 20 nm gold thin film in order to obtain better images. The magnetic properties were carried out with a VersaLab magnetometer (Quantum Design), for magnetic fields up to 3 T in the temperature range 50–350 K.

3. Results and discussion Fig. 1 shows the X-ray diffraction (XRD) pattern with Rietveld refinement of LaCrO3 (Fig. 1(a)) and LaCr0.5Al0.5O3 (Fig. 1(b)) samples, heat-treated at 1300 °C for 12 h. The Rietveld refinements of the patterns were performed starting from an orthorhombic phase, Pnma (62) indexed with the ICSD card-79344 for LaCrO3 and a rhombohedral phase, belonging to R-3c (167) space group, indexed with the ICSD card-164511 for LaCr0.5Al0.5O3 sample. XRD patterns were recorded also for the samples obtained just after combustion and those heat-treated at 500 °C (data not shown). LaCrO3 is formed just after combustion, but the impurity free halfdoped sample is only obtained after being heat-treated at 1300 °C for 12 h. Images of the powder obtained from the combustion reaction after calcination at 500 °C are shown in the inset of Fig. 1. There is a visible color difference between the pristine sample (greenish powder) and the half-doped sample (yellowish powder). The color of the LaCrO3 remains green after all heat treatments, but the half-doped sample (LaCr0.5Al0.5O3) change the color at high temperatures. After the combustion, this compound is yellow and darkens when the temperature increases changing to greenishyellow color at 1300 °C. The origin of the green color of LaCrO3 is well-established and is attributed to optical transition between the Cr 3d electrons [30]. The doping color dependence of LaCrO3, is until now, controversial. The yellow color obtained in La or O deficient LaCrO3 can be attributed to a Cr valence change, as observed in the SrTiO3 compound which becomes orange when doped with Cr [31]. Such valence change is not expected to occur in the half-doped (LaCr0.5Al0.5O3) compound. This is in concordance with the Cr valence obtained by a linear fit on the paramagnetic region of the magnetic susceptibility as a function of temperature, as shown in the Fig. 8, that indicates a valence state 3þ for the Cr in both compounds. In this case, the change of the color could be attributed to: 1- Changes in the content of La and/or O content; 2- Reduction of the distortions in the structure as show in Figs. 3 and 4; 3- Changes on the hybridization of the Cr 3d orbitals. Further investigations are necessary in order to elucidate the change of color in these compounds. A structural phase transition on the half-doped sample can be verified by the changes of the main peak located between 37° and 39° as shown in Fig. 2. It's known that the structural transition from orthorhombic-to-rhombohedral on the LaCrO3 compound may occur by increasing temperature [24] or pressure [28]. The partial substitution of the Cr3 þ by Al3 þ ion induces a structural phase transition from orthorhombic to rhombohedral structure. As


(121)

LaCrO3

(200)

LaCr0.5Al0.5O3

31,5

32,0

32,5

(104)

(110)

1300°C/12h (002)

Intensity (arb.units)

14501

33,0

33,5

2θ (°) Fig. 2. Zoom of the main peak of X-ray diffraction pattern for LaCrO3 (black line) and LaCr0.5Al0.5O3 (red line). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Fig. 4. Crystal structure obtained with program VESTA using the refined atomic coordinates of LaCr0.5Al0.5O3 sample.

Table 1 Crystallographic parameters obtained by Rietveld analysis.

Fig. 3. Crystal structure obtained with program VESTA using the refined atomic coordinates of LaCrO3 sample.

reported by Cordischi et al. [32] LaCr1 xAlxO3 presents a rhombohedral structure for xZ 0.2. Therefore, regardless the heat treatment temperature and the method used to prepare LaCr0.5Al0.5O3, this sample has rhombohedral structure at room temperature. In this work is shown that reducing the chemical pressure by doping also results in a structural transition from orthorhombicto-rhombohedral that also is followed by a reduction of the CrO6 octahedral distortion. The reduction of the distortion can be confirmed by the increase of the bonding angle B–O–B calculated from Rietveld refinement. In the undoped sample the B-O-B angle on the ab-plane is θ ¼162.03(0)° for Cr–O2–Cr and θ ¼156.18(8)° for Cr–O1–Cr that is very close to the value found by K. Oikawa et al. [24]. In half-doped sample, the B–O–B angle is θ ¼165.45(0)° for (Cr, Al)-O-(Cr, Al) that is very close to 180° and indicate a distortion reduction of the octahedral BO6. Figs. 3 and 4 show the crystal structure obtained from the parameters summarized in Table 1 using the VESTA software for LaCrO3 and LaCr0.5Al0.5O3 respectively. Figs. 5(a) and 5(b) show SEM images of LaCrO3 and LaCr0.5Al0.5O3, respectively. It's observed samples with particles of irregular morphologies with grain size around 200 nm. The backscattered electron imaging (data not shown) reveal that pure and half-doped samples have surface homogeneity, and no secondary phase could be observed. The Energy Dispersive X-ray Spectroscopy (EDS) done on pristine and half-doped samples are shown in Fig. 6. The gold (Au) signal is attributed to the conductive layer

Parameters

LaCrO3

LaAl0.5Cr0.5O3

Space group a (Å) b (Å) c (Å) α (°) β (°) γ (°) La x Y Z Frac. Uiso (Cr, Al) x Y Z Frac. Cr/Al Uiso O1 x Y Z Frac. Uiso O2 x Y Z Frac. Uiso Volume (Å3) Rp (%) Rwp (%) R (F2) χ2

Pnma 5.4789 7.7529 5.5148 90 90 90 0.0185 0.2500 0.0030 1.00 0.0038 0 0 0.5 1.00/ 0.0038 0.4985 0.2500 0.0741 1.00 0.0038 0.2879 0.0290 0.7342 1.00 0.0038 234.25 6.13 7.71 11.64 1.85

R-3c 5.4434 5.4434 13.2167 90 90 120 0 0 0.2500 0.99 0.0125 0 0 0 0.53/0.47 0.0125 0.5450 0.0000 0.2500 0.47 0.0223 – – – – – 339.16 5.34 6.98 3.64 1.24

deposit on the surface. We analyzed the ratio between the cations in A and B site of the perovskite, using the lines Al-K, Cr-L and LaM in different regions of the samples. In the pristine sample, we obtained a La/Cr ratio of 0.977 0.04. For half-doped samples, La/Cr, La/Al, La/(Cr þAl) and Cr/Al ratios were 1.60 70.01, 2.03 70.08, 0.89 70.01 and 1.277 0.06 respectively. These results give an indication of a small deficiency of La and Al on the samples probably due to the high temperature of thermal treatment. These results are in concordance with the Rietveld refinement where the better fit only was possible when including a La and Cr deficiency. Fig. 7 shows the temperature dependence of the magnetic susceptibility (χ ¼ Μ/Η) under Zero Field Cooled (ZFC) and Field


1.5

ZFC , FC , ,

LaCrO3 LaCr0.5Al0.5O3

H=10 KOe

1.0

-5

(10 emu/Oe g Cr)

14502

0.5 50

100

150

200

250

300

350

T (K) Fig. 7. ZFC and FC magnetic susceptibility (χ) versus temperature (T) for LaCrO3 (black) and LaCr0.5 Al0.5O3 (red) samples measured at H ¼10 kOe. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Fig. 5. Scanning Electron Microscopy (SEM) images for LaCrO3 (a) and LaCr0.5Al0.5O3 (b) samples.

LaCrO3

Cr-L O-K

Counts

LaCr0.5Al0.5O3

La-L Al- K

C-K

0

La-M

1

Cr-K La-L La-L

Au

La-L Cr-K

La-L

2

3

4

5

6

7

E(keV) Fig. 6. EDS analysis of LaCrO3 (black line) and LaCr0.5 Al0.5O3 (red line). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Cooled (FC) protocols for pure (black dots) and half-doped (red dots) sample. The Néel temperature was taken as the being the temperature given by the difference between the FC and ZFC curves. A strong decrease in the Néel temperature from 287 K (LaCrO3) to 140 K (LaCr0.5Al0.5O3) is observed.

Fig. 8. Inverse of the FC magnetic susceptibility versus temperature for pure sample (a) and half-doped (b) for H ¼10 kOe. The dashed line represents a fit according to the Curie-Weiss law. (For interpretation of the references to color in this figure, the reader is referred to the web version of this article.)

Fig. 8 shows the inverse of the FC magnetic susceptibility (χ 1) as a function of temperature (T) for pure (Fig. 8(a)) and half-doped (Fig. 8(b)) samples. The blue dashed line is the linear fit of the curves in the paramagnetic region in accordance with the CurieC

Weiss law χ= T − θ , where C is the Curie constant,

θ is the Weiss

temperature and T is the temperature. The negative value of the


4. Conclusion

LaCr0.5 Al0.5 O3 T = 50 K T = 150 K T = 300 K

4 0

M (10 μB /f.u.)

-4

-3

-3 M ( 1 0 μ B /f.u .)

8

0.4 0.0

-0.4 -1000

-8

μ

0

0

-30

-20

-10

14503

0

10

H (Oe)

20

1000

30

H (kOe) Fig. 9. Magnetization as a function of applied magnetic field for LaCr0.5Al0.5O3 at 50 K, 150 K and 300 K. The inset shows the low-field behavior at 50 K.

Weiss temperature indicates that pure and half-doped sample present an antiferromagnetic order. We can see from Figs. 7 and 8 that the structural transition induced by chemical pressure does not modify the antiferromagnetic order of the samples. A strong reduction of the Néel temperature ( TN ) and an increase of the Weiss temperature ( θ is observed, followed by a reduction of the frustration factor ( f = θ /TN )) from 9.02 for the pure sample to 2.29 for the halfdoped sample. This shows that frustration effects are reduced with increasing Al content, leading to a better stabilization of the antiferromagnetic ordering of the chromium atoms. The reduction of the Néel temperature in the compounds here studied is in concordance with the Bloch's rules, where the reduction of the chemical pressure induced an increase of the lattice parameter and consequently a reduction of the ordering temperature [27]. Similar results were obtained by Zhou et al. [28] using an external pressure. In this case, an increase of the external pressure increases the Néel temperature and also induce a shift of the spin alignment in the [111] direction of the octahedron. Further studies are necessary for a better understand the temperature and magnetic field dependences of the magnetic structure of the LaCr0.5Al0.5O3. To respond to this issue is necessary to use techniques such as neutron or synchrotron X-ray diffraction as a function of temperature and magnetic field. The Curie-Weiss temperatures for both samples were found to be negative, indicating a predominance of antiferromagnetic interaction between Cr3 þ ions. The experimental effective magnetic moments obtained from the high-temperature data were 3.80 mB for LaCrO3 and 2.58 mB for LaCr0.5Al0.5O3, As the Al3 þ does not have magnetic moment (S ¼0) the calculated magnetic moment is given by the expression μ=g x S(S + 1) μB where g = 2, x = 1 for pure sample and x = 0.5 for half doped sample. Assuming that all Cr ions have valence 3þ (S¼ 3/2) we obtain that the theoretical magnetic moment is 3.87 mB and 2.74 mB for pure and half-doped sample, respectively. These values are in concordance with those experimentally obtained, corroborating that a Cr3 þ state is indeed observed in both samples. Magnetization curves as a function of applied magnetic field for a half-doped sample at different temperatures are shown in Fig. 9. We can observe a typical paramagnetic behavior at 150 K and 300 K. At 50 K it is observed a small opening of the magnetic isotherm which can be attributed to the canting of the Cr3 þ spins antiferromagnetic ordered.

LaCrO3 pure and Al half-doped samples prepared by combustion method were successful obtained. The pristine sample (LaCrO3) presents an orthorhombic structure with space group Pnma (62) and the Al half-doped sample (LaAl0.5Cr0.5O3) is formed in a rhombohedral structure with space group R-3c, due to the difference of the ionic radius of Al3 þ and Cr3 þ . SEM micrographs reveal that the samples exhibit a spherical formation with size around 200 nm and irregular morphologies. EDS analysis reveals a small deficiency of La in the half-doped sample by EDS. The negative value of Weiss temperature indicates that pure and halfdoped sample orders antiferromagnetically. A strong reduction of the magnetic transition temperature is observed in the half-doped sample. A small irreversibility between the ZFC and FC magnetization curves below 140 K and a small opening of the hysteresis loop at 50 K is observed in the half-doped sample.

Acknowledgments This work was supported by the Brazilian science agencies CAPES (grant PNPD 2498/2011), CNPq (grants 443458/2014-6, 307552/2012-8 and 141911/2012-3) and FACEPE (grant APQ-1038/ 1.05-12).

References [1] J.B. Goodenough, Electronic and ionic transport properties and other physical aspects of perovskites, Rep. Prog. Phys. 67 (2004) 1915. [2] J. Dho, N.H. Hur, Magnetic and transport properties of lanthanum perovskites with B-site half doping, Solid State Commun. 138 (2006) 152. [3] T.-C. Han, I.-Chu Wu, and H.-K. Hsu, Effects of Cr doping on the magnetic properties of multiferroic YMnO3, J. Appl. Phys. 115 (2014) 17D906. [4] H. Naganuma, J. Miura, S. Okamura, Ferroelectric, electrical and magnetic properties of Cr, Mn, Co, Ni, Cu added polycrystalline BiFeO3 films, Appl. Phys. Lett. 93 (2008) 052901. [5] H. Zhang, W. Liu, P. Wu, X. Hai, M. Guo, X. Xi, J. Gao, X. Wang, F. Guo, X. Xu, C. Wang, G.L.W. Chu, S. Wang, Novel behaviors of multiferroic properties in Na-Doped BiFeO3 nanoparticles, Nanoscale 6 (2014) 10831. [6] G. Dong, G. Tan, Y. Luo, W. Liu, A. Xia, H. Ren, Charge defects and highly enhanced multiferroic properties in Mn and Cu co-doped BiFeO3 thin films, Appl. Surf. Sci. 305 (2014) 55. [7] T.D. Rao, R. Ranjith, S. Asthana, Enhanced magnetization and improved insulating character in Eu substituted BiFeO3, J. Appl. Phys. 115 (2014) 124110. [8] M. Imada, A. Fujimori, Y. Tokura, Metal-insulator transitions, Rev. Mod. Phys. 70 (1998) 1039. [9] K.H.L. Zhang, Y. Du, P.V. Sushko, M.E. Bowden, V. Shutthanandan, S. Sallis, L.F. J. Piper, S.A. Chambers, Hole-induced insulator-to-metal transition in La1 xSrxCrO3 epitaxial films, Phys. Rev. B 91 (2015) 155129. [10] S. Mathews, R. Ramesh, T. Venkatesan, J. Benedetto, Ferroelectric field effect transistor based on epitaxial perovskite heterostructures, Science 276 (1997) 238. [11] D.M. Newns, Y. Heights, J.Z. Sun, M. Lake, Ferroelectric Drive for Data Storage, United States Patent, US 6515957 B1, 2003. [12] K. Ito, H. Takahashi, Magnetic read head and hard disk drive, United States Patent, US 7209328 B2, 2007. [13] M. McCormack, S. Jin, T.H. Tiefel, R.M. Fleming, Julia M. Phillips, R. Ramesh, Very large magnetoresistance in perovskite-like La-Ca‐Mn-O thin films, Appl. Phys. Lett. 64 (1994) 22. [14] S. Geller, V.B. Bala, Crystallographic studies of perovskite-like compounds. II. Rare earth alluminates, Acta Cryst. 9 (1956) 1019. [15] C.J. Howard, B.J. Kennedy, B.C. Chakoumakos, Neutron powder diffraction study of rhombohedral rare-earth aluminates and the rhombohedral to cubic phase transition, J. Phys. Condens. Matter 12 (2000) 349. [16] P. Bouvier, J. Kreisel, Pressure-induced phase transition in LaAlO3, J. Phys. Condens. Matter. 14 (2002) 3981. [17] J. Zylberberg, Z.-G. Ye, Improved dielectric properties of bismuth-doped LaAlO3, J. Appl. Phys. 100 (2006) 086102. [18] J.M. Phillips, Substrate selection for high-temperature superconducting thin films, J. Appl. Phys. 79 (1996) 1829. [19] A. Ohtomo, H.Y. Hwang, A high-mobility electron gas at the LaAlO3/SrTiO3 heterointerface, Nature 427 (2004) 423. [20] N. Reyren, S. Thiel, A.D. Caviglia, L. Fitting Kourkoutis, G. Hammerl, C. Richter, C.W. Schneider, T. Kopp, A.-S. Retschi, D. Jaccard, M. Gabay, D.A. Muller, J.M. Triscone, J. Mannhart, Superconducting interfaces between insulating

14504


oxides, Science 317 (2007) 1196. [21] A. Brinkman, M. Huijben, M. Van Zalk, J. Huijben, U. Zeitler, J.C. Maan, W.G. Van der Wiel, G. Rijnders, D.H.A. Blank, H. Hilgenkamp, Magnetic effects at the interface between non-magnetic oxides, Nat. Mater. 6 (2007) 493. [22] G. Pudmich, B.A. Boukamp, M. Gonzalez-Cuenca, W. Jungen, W. Zipprich, F. Tietz, Chromite/titanate based perovskites for application as anodes in solid oxide fuel cells, Solid State Ion. 135 (2000) 433. [23] J.W. Fergus, Lanthanum chromite-based materials for solid oxide fuel cell interconnects, Solid State Ion. 171 (2004) 1. [24] K. Oikawa, T. Kamiyama, T. Hashimoto, Y. Shimojyo, Y. Morii, Structural phase transition of orthorhombic LaCrO3 studied by neutron powder diffraction, J. Solid State Chem. 154 (2000) 524. [25] S. Geller, P.M. Raccah, Phase transitions in perovskitelike compounds of the rare earths, Phys. Rev. B 2 (1970) 1967. [26] P. Barrozo, J. Albino Aguiar, Ferromagnetism in Mn half-doped LaCrO3, J. Appl. Phys. 113 (2013) 17E309.

[27] D. Bloch, The 103 law for the volume dependence of superexchange, J. Phys. Chem. Solids 27 (1966) 881. [28] J.-S. Zhou, J.A. Alonso, A. Muñoz, M.T. Fernndez-Díaz, J.B. Goodenough, Magnetic structure of LaCrO3 perovskite under high pressure from in situ neutron diffraction, Phys. Rev. Lett. 106 (2011) 057201. [29] S.R. Jain, K.C. Adiga, V.R.P. Verneker, A new approach to thermochemical calculations of condensed fuel-oxidizer mixtures, Combust. Flame 40 (1981) 71. [30] K.P. Ong, P. Blaha, P. Wu, Origin of the light green color and electronic ground state of LaCrO3, Phys. Rev. B 77 (2008) 073102. [31] G.I. Meijer, U. Staub, M. Janousch, S.L. Johnson, B. Delley, T. Neisius, Valence states of Cr and the insulator-to-metal transition in Cr-doped SrTiO3, Phys. Rev. B 72 (2005) 155102. [32] D. Cordischi, S. De Rossi, M. Faticanti, G. Minelli, P. Porta, LaAl1-xCrxO3 perovskite-type solid solutions: structural, electronic, magnetic properties and catalytic activity towards CO oxidation, Phys. Chem. Chem. Phys. 4 (2002) 3085.