Synthesis, characterization and sensitivity tests of perovskite-type LaFeO3 nanoparticles in CO and propane atmospheres

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Synthesis, characterization and sensitivity tests of perovskite-type LaFeO3 nanoparticles in CO and propane atmospheres L. Gildo-Ortiz a,n, J. Reyes-Gómez b, J.M. Flores-Álvarez b, H. Guillén-Bonilla c, M. de la L. Olvera d, V.M. Rodríguez Betancourtt e, Y. Verde-Gómez f, A. Guillén-Cervantes g, J. Santoyo-Salazar g a

Nanociencias y Nanotecnología, CINVESTAV, IPN, 07360 México Facultad de Ciencias, Universidad de Colima, 28045 Colima, México c Departamento de Ingeniería de Proyectos, CUCEI, Universidad de Guadalajara, 44410 Jalisco, México d Departamento de Ingeniería Eléctrica-SEES, CINVESTAV, IPN, 07360 México e Departamento de Química, CUCEI, Universidad de Guadalajara, 44410 Jalisco, México f Instituto Tecnológico de Cancún, 75000 Quintana Roo, México g Departamento de Física, CINVESTAV, IPN, 07360 México b

art ic l e i nf o

a b s t r a c t

Article history: Received 6 April 2016 Received in revised form 3 September 2016 Accepted 4 September 2016

Nanoparticles of perovskite-type LaFeO3 were synthesized by a simple process using stoichiometric lanthanum and iron nitrates, ethylenediamine, and distilled water as a solvent. Microwave radiation, with a power of
350 W, was applied for solvent evaporation. The obtained precursor powders were calcined at 200, 400, 500, 600 and 700 °C in static air, and analyzed by X-ray diffraction and cyclic voltammetry. The samples showed catalytic activity and high physical and chemical stability. The calcined powders at 700 °C were analyzed through scanning and transmission electron microscopy; agglomerated nanoparticles, forming a porous structure, were observed with an average size of 28 nm. Their magnetic properties correspond to magnetization up to 0.83 emu/g and coercivity of 182 Oe. Pellets from these powders were prepared to measure the sensitivity to CO and propane gases, obtaining high performance at different gas concentrations and operation temperatures. & 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

Keywords: A. Powders: Chemical preparation B. Electron microscopy D. Perovskites E. Sensors

1. Introduction Advances in the preparation of new transition metal oxides have allowed the development of complex materials such as the perovskite-type oxides. These compounds are grouped among the advanced materials due to their special physical and chemical properties [1–10]. Materials with a perovskite-type structure take the general form of ABO3 [11,12], where A stands generally for a lanthanide or an alkaline earth element, such as La, Pr, Nd, Gd, Sm and Sr; B represents a transition metal, mainly Co, Fe and Ni [13]. Several combinations that can be accomplished through A and B yield a great variety of compounds with highly relevant chemical and physical properties for technological applications [14], e.g. gas sensors, electrodes for solid oxide fuel cells (SOFC), catalysts, magnetic devices, among others [15–20]. Since past decades, several investigation groups have used different synthesis methods to obtain perovskite-type materials, being the ceramic method the n

Corresponding author. E-mail address: [email protected] (L. Gildo-Ortiz).

most commonly employed [14]. Nevertheless, other chemical routes have been explored [21], such as the synthesis of Sm1  xBaxCoO3 through an aqueous solution method [22], LaFeO3 through sol-gel route [23], BaTiO3 by means of a sol-precipitation process [24] and LaCoO3 through a glycine nitrate (G/N) plus EDTA route [25]. These synthesis routes allowed obtaining nanomaterials with high porosity and specific morphologies of a great relevance due to its potential applications. Recently, the research on perovskite-type oxides as possible gas sensors has been extensive, due to the high thermal stability, catalytic activity and semiconductor behavior of the oxides [26,27]. For example, CaxPb1  xTiO3 has been studied as a possible humidity sensor [28], SmFeO3 is considered for the detection of NO2 and CO [29], and SrFeO3 is a strong candidate as an ethanol vapors sensor [17]. The lanthanum ferrite, LaFeO3, is being nowadays heavily investigated because it shows an excellent electric response in different gases. Different authors [30–33] report the successful use of this perovskite-type oxide, with different morphologies (ranging from thin films to hollow fibers) for detecting triethylamine, CO, NO and NO2. A pending issue is, notwithstanding the foregoing, to determine the best microstructure

http://dx.doi.org/10.1016/j.ceramint.2016.09.027 0272-8842/& 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

Please cite this article as: L. Gildo-Ortiz, et al., Synthesis, characterization and sensitivity tests of perovskite-type LaFeO3 nanoparticles in CO and propane atmospheres, Ceramics International (2016), http://dx.doi.org/10.1016/j.ceramint.2016.09.027i

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of the oxide for a better application. In this work, LaFeO3 nanoparticles were synthesized making strong emphasis on the microstructure of the oxide, and its physical and chemical properties were analyzed in order to explore its possible application as a carbon monoxide and propane sensor.

2. Experimental 2.1. Synthesis of LaFeO3 An aqueous synthesis route containing ethylenediamine was used to obtain the oxide. The synthesis was as follows: three solutions were prepared using 0.004 mol of La(NO3)3  6H2O (Alfa Aesar, 99%), 0.004 mol of Fe(NO3)3  9H2O (Monterrey, 98%) and 2 mL of ethylenediamine (Sigma, Z99%) using 5 mL of distilled water as a solvent. Each solution was stirred at 375 rpm for 15 min; thereafter, the ethylenediamine and ferric nitrate solutions were mixed (yielding a fine brownish precipitate) and the lanthanum nitrate was slowly added to such mixture. The resulting colloidal suspension was continuously stirred at room temperature during 24 h. The solvent was then evaporated by means of a typical microwave oven (General Electric, model JES769WK) in cycles of 60–90 s at
350 W (the suspension's temperature was of 90 °C during each cycle). After the solvent's evaporation, a brownish paste was obtained, which was then heated at 200 °C during 8 h. The resulting precursor powder was divided in 4 portions, which were calcined at 400, 500, 600, and 700 °C, respectively. The calcination was as follows: starting at room temperature, the powders were heated at a rate of 100 °C/h in a set point control furnace (Neycraft Vulcan, model A-550); thereafter, the sample was kept at the given calcination temperature for 5 h. 2.2. LaFeO3 powders characterization All the calcined powders were analyzed by means of XRD (RIGAKU SmartLab diffractometer, CuKα radiation, 2θ scanning angle of 20–70°, at 0.02° steps with duration of 1 s). The microstructures were observed using SEM (JEOL JSM-6390LV, high vacuum, secondary electron emission). In order to observe the oxide nanoparticles by means of TEM (JEOL JEM-2010, accelerating voltage of 200 kV), the powders were dispersed in isopropyl alcohol for 5 min and were placed on a formvar carbon copper grid, 400 mesh. The magnetic characterization was made using a magnetometer (VSM-VersaLab CryoFree), applying a cyclic magnetic field in the range 30 a þ30 kOe, at room temperature.

2.3.2. Solutions The working solution was a Briton-Robinson buffer of pH 2 with 0.15 mol L  1 of potassium chloride as electrolyte. The buffer was prepared mixing equal volumes (0.04 mol L  1) of boric, acetic and phosphoric acids. 2.3.3. Instrumentation The voltamperometric tests were performed using a potentiostat (PAR, model VersaStat 3) and software (VersaStudio v2.20.4631). A three-electrodes cell was used: the MCPEs as working electrodes (surface area: 7.067 0.01 mm2), a graphite rod (Alfa Aesar, Johnson Matthey 99.9995%, surface area: 0.857 0.01 cm2) as a counter electrode, and a saturated calomel electrode (SCE) as the reference electrode. The results are reported as potential vs. SCE potential. 2.4. Sensitivity tests The gas sensitivity tests of the LaFeO3 were performed in two atmospheres: carbon monoxide (CO) and propane (C3H8). For the tests, the electrical resistance of LaFeO3 pellets (diameter: 12 mm, thickness: 500 mm) was recorded at different temperatures and gas concentrations. The pellets were prepared with 0.5 g of LaFeO3 powders pressed at a rate of 0.5 t / mm2 for 90 min with a manual pressure machine (Simplex Ital Equip-25 t). Two ohmic contacts were attached to the pellets’ surface by means of colloidal silver (Alfa Aesar,4 99%). The pellets were placed inside a measurement chamber in a vacuum of 10  3 Torr. The partial pressure inside the chamber, as a reference for the gas concentration, was continuously monitored by means of a simple detector (Leybold, model TM20). The electrical resistance was recorded using a digital multimeter (Keithley 2001). The gas detection system was set up as reported elsewhere [35]. The gas sensitivity (S) was calculated by means of the relative difference of electrical conductances: S¼ (GG–G0)/G0 where GG and G0 are the electrical conductances in the sampled gas (CO or C3H8) and air, respectively.

3. Results and discussion 3.1. XRD analysis Fig. 1 shows the X-ray diffraction patterns of the calcined powders at 200, 400, 500, 600 and 700 °C. The main diffraction peaks corresponding to a perovskite-type LaFeO3 are present since

2.3. Voltamperometric analysis using carbon paste electrodes (CPE) 2.3.1. CPEs preparation Unmodified CPEs were prepared as reported elsewhere [34]; a mixing 0.2 g of graphite powder (Alfa-Aesar, particle size: 2– 15 mm, 99.9995% purity) and 100 μL of paraffin oil (Golden Bell, ρ ¼ 0.85 g cm  3) in an agate mortar. The resulting paste was packed inside a polyethylene tube (inner diameter: 3 mm, length: 7 cm) with a plug for pressing the paste or for getting rid of it when its reaction finished. The electric contact of the paste was made using a platinum wire welded to a copper wire. By exuding 0.1 mm of paste from the tube and polishing the new surface over a paper sheet, the electrode's surface was regenerated before each experiment. After preparation, the electrodes were immersed in deionized water for 24 h. The modified CPEs were prepared mixing 0.16 g of graphite powder, 0.04 g of the synthesized powders, 100 μL of paraffin oil (this ratio graphite/sample/oil turned out to be the optimum) and using the procedure before mentioned.

Fig. 1. X-ray diffraction patterns of the calcined powders at 200, 400, 500, 600 and 700 °C.

Please cite this article as: L. Gildo-Ortiz, et al., Synthesis, characterization and sensitivity tests of perovskite-type LaFeO3 nanoparticles in CO and propane atmospheres, Ceramics International (2016), http://dx.doi.org/10.1016/j.ceramint.2016.09.027i

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the sample calcined at 200 °C. Such peaks are located on the 2θ positions (in °): 22.6, 32.3, 38.1, 39.7, 41.4, 46.2, 47.8, 52.1, 53.6, 57.4 and 67.4, which can be indexed, according to the file PDF 01-0880641, to the diffraction planes as follow: (001), (121), (112), (220), (131), (202), (212), (103), (311), (123) and (242), respectively. This corresponds to an orthorhombic crystal structure with space group Pnma and cell parameters: a ¼5.56 Å, b¼ 7.85 Å and c ¼5.55 Å. The unit cell of LaFeO3 consists of 4 perovskite-type distorted units [36]. It is also shown in Fig. 1 that the peak intensity rises with the calcination temperature, which suggests that the samples’ crystallinity improves with temperature. The peak width is an indication of the presence of nanocrystalline materials. An important aspect of our work is the fact that the synthesis temperatures of the LaFeO3 were relatively lower than those reported in the literature. For example, using solid state reaction methods, and lanthanum and iron oxides as precursor mixtures, reported temperatures have been over 1300 °C [37]. And by means of “soft chemistry methods”, temperatures between 500 and 950 °C have been reached [38]. Therefore, according to all consulted reports, the microwave-assisted aqueous solution method, used here, can be regarded as an economical and practical route for synthesizing the LaFeO3, because diffraction peaks, though of low intensity, can be found even from
200 °C. 3.2. Electrochemical analysis by means of cyclic voltamperometry Solid-state gas sensors are based on resistance changes caused by exposure of the sensor surface to a target species. Gas sensors should exhibit a stable and reproducible response for a period of time. Therefore, used gas-sensing materials should be characterized by high chemical stability. In this work, the physical and chemical stability of LaFeO3 was analyzed by electrochemical tests. This property provides an opportunity to work in different mediums [39]. Two cyclic voltamperograms with only CPE are shown in Fig. 2. The potential scanning began in the positive direction in the CV forward and in the negative direction in the CV reverse, starting both with an open circuit potential (OCP) of 0.5 V in a range of 2 to  2 V at a scan rate of 100 mV s  1. In the CV forward, 5 peaks are mainly seen, and were denoted as A, B, C, D and E, respectively, while in the CV reverse, only two peaks, A and E, are observed. The reduction peak E at  2 V is due to the H2 gas formation by electrolysis (in both cases). Peak A, which starts at 1.3 V, is due to the addition of the species oxidation of the electrolyte and the buffer, and the O2 gas formation by the electrolysis. The reduction currents B (at 0.5 V), C (at 1 V) and D (at  1.6 V) appear only when the oxidation peak A is

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Fig. 3. Cyclic voltamperograms obtained with the perovskite-MCPEs. The potential scanning started in the positive direction.

generated. Peak B only forms when the electrolyte is KCl, hence the peak is linked to the electrolyte’s reduction. Peaks C and D only appear when the electrolyte combines with the B-R buffer, hence they are related to the buffer's reduction. Voltamperograms obtained with the perovskite-MCPE are depicted in Fig. 3. In all cases, the potential scanning began in the positive direction with an OCP of 0.5 V in a range of 2 to  2 V at 100 mV s  1. The same current peaks were obtained as the CPE, which shows that the powders calcined at, and above, 400 °C were not chemically nor physically modified, even with the used acidic pH (¼2). In addition, because of a no redox peak was observed, no other compound was formed during the reaction. Comparing the peaks linked to the electrolyte's reduction (peak B) for both types of electrodes (CPE and perovskite-MCPEs), a difference in the potentials is evident: 0.5 V and
0.2 V, respectively. This displacement to lower potentials means that the electrolyte's reduction is being promoted by the use of the perovskite-type oxide [40], i.e. the reduction reaction is being catalyzed [41]. The voltamperogram of the calcined sample at 200 °C shows a difference with those of the other perovskites. The reduction and oxidation peaks F and F′, respectively, depend on the oxidation peak A, because they will not appear if the latter is not generated. Such peaks are an indication that other species, different to the perovskite, are present and chemically active. Gorbunov et al [42]. report that the ethylenediamine and the transition-metal nitrates generate complexes which decompose at temperatures above 200 °C, which suggests that peaks F and F′ are due to redox reactions of metallic complexes still in the sample. The diffractogram corresponding to the mentioned sample (see Fig. 1), which shows lower crystallinity, indicates the existence of other species formed during the synthesis process. This results demonstrate the high physical and chemical stability of LaFeO3 samples synthesized at, and above, 400 °C. 3.3. SEM analysis

Fig. 2. Cyclic voltamperograms obtained with the CPE. The potential scanning was in the positive (forward) and the negative (reverse) directions.

Fig. 4 shows two typical SEM micrographs of LaFeO3 powders after calcination at 700 °C. These micrographs present two magnifications: a) 200X and b) 5000X. A sponge-like morphology can be seen in Fig. 4(a). This morphology is the result of the agglomeration of very small particles, which have a lot of macropores (size: 2–15 mm) distributed along their surface. At a greater magnification (5000X, Fig. 4b), smaller pores (
0.3 mm) also can be observed. This porosity can be attributed to particle coalescence due to the chelating effect of the ethylenediamine and the released gases during the thermal decomposition of the organic material in the sample [43].

Please cite this article as: L. Gildo-Ortiz, et al., Synthesis, characterization and sensitivity tests of perovskite-type LaFeO3 nanoparticles in CO and propane atmospheres, Ceramics International (2016), http://dx.doi.org/10.1016/j.ceramint.2016.09.027i

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Fig. 4. SEM images of LaFeO3 powders (calcined at 700 °C) at two magnifications: a) 200X and b) 5000X.

3.4. TEM analysis Fig. 5 shows two TEM images of the oxide's surface from sample obtained at 700 °C. It is evident an agglomeration of LaFeO3 nanoparticles with almost the same particle size in the range of 9.1–54 nm with an average sized estimated of 27.7 nm, with a standard deviation of 9.5 nm (Fig. 6). More details of the surface features can be found at higher magnifications (Fig. 5b), where irregularities in the shape and some pores of size
5 nm can be identified. The high porosity of the LaFeO3 surface is fully evident. Inset in Fig. 5(b) shows also a selected area electron diffraction pattern (SAED) to confirm the oxide's polycrystalline nature. The effect of ethylenediamine in the formation of very small structures of materials, like nanorods, nanowires, and nanoparticles, has been discussed in previous studies. The microstructure is influenced by the presence of ethylenediamine [43,44] because it acts as a template, which at a first step is incorporated to the inorganic grid and afterwards escapes leaving nanocrystals of certain morphology [45]. These morphologies follow the crystallization principles of LaMer and Dinegar [43,44,46]. 3.5. Magnetic properties The results shown in what follows correspond to the LaFeO3 powders synthesized at 700 °C. Fig. 7 shows a hysteresis loop of the LaFeO3 measured at room temperature and a maximum applied field (Hmax) of 30 kOe, yielding a maximum magnetization (Mmax) of 0.83 emu/g, which indicates that the LaFeO3 exhibits a weak ferromagnetic behavior. The coercivity (HC) was 182 Oe.

Fig. 6. Particle size distribution of LaFeO3 synthesized at 700 °C.

These results are in agreement with those reported by Tang et al [47]. with saturation magnetization M of 0.514 emu/g for nanoparticles with sizes ranging 80–100 nm of the same oxide, synthesized by burning the precursor solutions using microwave radiation (at 850 W). The magnetization can be changed according the particle size, shape and its distribution, the remanence energy is reduced as a function of particle size. This is dissipated by the nanoparticles as the particle size is diminished [48].

Fig. 5. TEM images of the LaFeO3 nanoparticles (prepared at 700 °C) and electron diffraction pattern (inset).

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Fig. 7. Hysteresis loop M–H of LaFeO3 nanoparticles (synthesized at 700 °C), measured at 300 K.

Fig. 9. Sensitivity of LaFeO3 (synthesized at 700 °C) to several propane gas concentrations and temperatures.

3.6. Gas sensitivity

sensitivities were 0, 0.47, 1.21, 1.57, 2.05 and 3.04 for propane concentrations of 0, 5, 50, 100, 200, and 300 ppm, respectively, while at 350 °C the sensitivity increases to 0, 0.83, 2.06, 4, 11.2 and 31.4 for the same propane concentrations range. The observed sensitivity trend has been widely reported in the literature for different oxides [43,49,50]. The gas sensing mechanism of materials like the LaFeO3 involves the chemisorption of the oxygen and its subsequent reaction with the sampled gas. In fact, the ionization state of the chemisorbed oxygen depends on the working temperature: below 150 °C, molecular O2  species are mainly found; above 150 °C, more reactive O  and O2  atomic species dominate [51,52]. The formation of atomic oxygen species at high temperatures increases the solid-gas interactions, hence the sensitivity of the gases is improved. In addition, the sensitivity rises with the gas concentration, no matter what gas it is, since the more gas concentration the more desorption reactions. At low temperatures (o150 °C) there is no enough thermal energy to promote desorption, no matter the gas concentration. In addition, the sensitivity decreased when the test gases were removed from the chamber, indicating that LaFeO3 nanoparticles had a high performance for the different gas concentrations and temperatures. The gas sensitivity results were compared with similar previous works finding that we have succeeded obtaining a

Figs. 8 and 9 show the sensitivities of the LaFeO3 nanoparticles (synthesized at 700 °C) as a function of the gas concentrations. Carbon monoxide sensitivity tests were performed at the following gas concentrations: 0, 5, 50, 100 and 200 ppm and at temperatures: 23, 150, 250 and 350 °C. The sensitivity, as a function of the CO concentration, is shown in Fig. 8(a); a zoom of the temperatures 23, 150 and 250 °C is depicted in Fig. 8(b). At 23 and 150 °C, the LaFeO3 did not show variation of the sensitivity to any CO concentration. However, when the CO was injected to the measurement chamber at 250 and 350 °C, variations of the oxide's electrical resistance were detected. At 250 °C, the calculated sensitivities were 0, 0.03, 0.04, 0.06 and 0.09 for CO concentrations of 0, 5, 50, 100 and 200 ppm, respectively, while at 350 °C the sensitivities increased to 0, 0.08, 1.08, 6.11 and 17 for the same CO concentrations range. It is evident that LaFeO3 is clearly sensitive to concentration change of CO, and that sensitivity is affected by the temperature. The sensitivity tests in propane, with the same temperatures as the CO, are shown in Fig. 9. Again, below 150 °C no significant variations on the electrical resistance were found, but only when the propane was injected at 250 and 350 °C (like for the CO) a variation on the sensitivity was observed. At 250 °C, the calculated

Fig. 8. a) Sensitivity of LaFeO3 (synthesized at 700 °C) to several CO gas concentrations and temperatures, b) zoom to the range 23–250 °C.

Please cite this article as: L. Gildo-Ortiz, et al., Synthesis, characterization and sensitivity tests of perovskite-type LaFeO3 nanoparticles in CO and propane atmospheres, Ceramics International (2016), http://dx.doi.org/10.1016/j.ceramint.2016.09.027i

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better sensitivity. For example, ZnSb2O6 showed maximum sensitivities of
7 (CO) and
1.5 (propane) at a temperature of 250 °C and a gas concentration of 300 ppm [53]; for CoSb2O6, the maximum sensitivities were
7 (CO) and
5 (propane) at 350 °C and a gas concentration of 300 ppm [49], while ZnO showed a maximum sensitivity of
6 at 300 °C and a propane concentration of 300 ppm [35]. A sensitivity of
10 (CO) and
40 (propane) was reached for perovskite-type LaCoO3 nanoparticles (average size of 70 nm) at 350 °C and a gas concentration of 200 and 300 ppm, respectively [43]. Part of this success is due to the fact that the gas response of materials depends on the microstructure. The gas sensitivity of the sensor material is enhanced with decreasing particle size down to the nanometer scale. In addition, perovskite oxides can provide microstructural and morphological stability to improve the sensor performance [54].

[9]

[10]

[11]

[12] [13]

[14] [15]

4. Conclusions

[16]

Porous LaFeO3 nanoparticles were synthesized by means of a microwave-assisted aqueous solution method. This is an interesting alternative route for the synthesis of such perovskite-type oxides because it can be successfully accomplished at lower temperatures than those employed with other methods. The LaFeO3 powders prepared at and above 400 °C exhibited great physical and chemical stability, apart from the catalytic activity they showed during the electrochemical tests. The magnetic behavior of the oxide was relatively weak, with a maximum magnetization of 0.83 emu/g and a coercivity of 182 Oe. The LaFeO3 nanoparticles were very sensitive to CO and propane at different gas concentrations and working temperatures. Maximum values of the sensitivity were approximately 17 and 31 for CO and propane respectively, at the maximum gas concentration and the highest temperature. Our results greatly encourage the use of this oxide, especially prepared by our method, as a gas sensor.

[17] [18]

[19]

[20]

[21] [22] [23] [24]

[25] [26]

Acknowledgments

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Lorenzo Gildo Ortiz is thankful to Consejo Nacional de Ciencia y Tecnología (CONACyT) for the postdoctoral fellowship received (convocatory 2016-3, 41560). Special thanks to Marcela Guerrero Cruz and Darío Pozas Zepeda for their technical assistance during the development of this work.

[28]

References

[31]

[1] D.D. Athayde, D.F. Souza, A.M.A. Silva, D. Vasconcelos, E.H.M. Nunes, J.C. Diniz Da Costa, W.L. Vasconcelos, Review of perovskite ceramic synthesis and membrane preparation methods, Ceram. Int. 42 (2016) 6555–6571. [2] P.H. Tchoua-Ngamou, N. Bahlawane, Chemical vapor deposition and electric characterization of perovskite oxides LaMO3 (M ¼ Co, Fe, Cr and Mn) thin films, J. Solid State Chem. 182 (2009) 849–854. [3] H. Abdullah, M.S. Zulfakar, S.K. Chen, Effect of Mn-site for Al substitution on structural, electrical and magnetic properties in La0.67Sr0.33Mn1  xAlxO3 thin films by sol-gel method, J. Nanomater. 2014 (2014) 9. [4] K. Kimura, K. Wagatsuma, T. Tojo, R. Inada, Y. Sakurai, Effect of composition on lithium-ion conductivity for perovskite-type lithium-strontium-tantalum-zirconium-oxide solid electrolytes, Ceram. Int. 42 (2016) 5546–5552. [5] M.L. Norton, H.Y. Tang, Superconductivity at 32 K in electrocrystallized Ba-KBi-O, Chem. Mater. 3 (1991) 431–434. [6] A.K. Azad, J. Zaini, P.I. Petra, L.C. Ming, S.-G. Eriksson, Effect of Nd-doping on structural, thermal and electrochemical properties of LaFe0.5Cr0.5O3 perovskites, Ceram. Int. 42 (2016) 4532–4538. [7] G. Carabalí, E. Chavira, I. Castro, E. Bucio, L. Huerta, J. Jiménez-Mier, Novel solgel methodology to produce LaCoO3 by acrylamide polymerization assisted by γ-irradiation, Radiat. Phys. Chem. 81 (2012) 512–518. [8] L.M. Rodríguez-Martínez, J.P. Attfield, Structural effects of cation size variance

[29]

[30]

[32]

[33]

[34]

[35]

[36]

[37]

[38]

in magnetoresistive manganese oxide perovskites, Chem. Mater. 11 (1999) 1504–1509. S.A. Sunshine, L.F. Schneemeyer, T. Siegrist, D.C. Douglass, J.V. Waszczak, R. J. Cava, E.M. Gyorgy, D.W. Murphy, Stabilization of strontium analogues of barium yttrium cuprate perovskites via chemical substitution, Chem. Mater. 1 (1989) 331–335. H. Tavakkoli, M. Yazdanbakhsh, Fabrication of two perovskite-type oxide nanoparticles as the new adsorbents in efficient removal of a pesticide from aqueous solutions: kinetic, thermodynamic, and adsorption studies, Microporous Mesoporous Mater. 176 (2013) 86–94. J.D.G. Fernandes, D.M.A. Melo, L.B. Zinner, C.M. Salustiano, Z.R. Silva, A. E. Martinelli, M. Cerqueira, C.A. Júnior, E. Longo, M.I.B. Bernardi, Low-temperature synthesis and single-phase crystalline LaNiO3 perovskite via Pechini method, Mater. Lett. 53 (2002) 122–125. C.N.R. Rao, The world perovskite oxides: from dielectrics to superconductors, Phys. C. 153–155 (1988) 1762–1768. Y. Wang, X. Yang, L. Lu, X. Wang, Experimental study on preparation of LaMO3 (M ¼ Fe, Co, Ni) nanocrystals and their catalytic activity, Thermochim. Acta 443 (2006) 225–230. F. Li, H. Zheng, D. Jia, X. Xin, Z. Xue, Synthesis of perovskite-type composite oxides nanocrystals by solid-state reactions, Mater. Lett. 53 (2002) 282–286. A. Worayingyong, P. Kangvansura, S. Kityakarn, Schiff base complex sol–gel method for LaCoO3 perovskite preparation with high-adsorbed oxygen, Coll. Surf. A 320 (2008) 123–129. M. Popa, J.M. Calderon-Moreno, Lanthanum cobaltite nanoparticles using the polymeric precursor method, J. Eur. Ceram. Soc. 29 (2009) 2281–2287. Y. Wang, J. Chen, X. Wu, Preparation and gas-sensing properties of perovskitetype SrFeO3 oxide, Mater. Lett. 49 (2001) 361–364. J. Prado-Gonjal, A.M. Arévalo-López, E. Morán, Microwave-assisted synthesis. A fast and efficient route to produce LaMO3 (M ¼ Al, Cr, Mn, Fe, Co) perovskite materials, Mater. Res. Bull. 46 (2011) 222–230. D. Kuscer, J. Holc, M. Hrovat, D. Kolar, Correlation between the defect structure, conductivity and chemical stability of La1  ySryFe1  xAlxO3-δ cathodes for SOFC, J. Eur. Ceram. Soc. 21 (2001) 1817–1820. A. Nemudry, M. Weiss, I. Gainutdinov, V. Boldyrev, R. Schollhorn, Room temperature electrochemical redox reactions of the defect perovskite SrFeO2.5 þ x, Chem. Mater. 10 (1998) 2403–2411. M. Popa, M. Kakihana, Synthesis of lanthanum cobaltite (LaCoO3) by the polymerizable complex route, Solid State Ion. 151 (2002) 251–257. E. Delgado, C.R. Michel, CO2 and O2 sensing behavior of nanostructured barium-doped SmCoO3, Mater. Lett. 60 (2006) 1613–1616. J. Feng, T. Liu, Y. Xu, J. Zhao, Y. He, Effects of PVA content on the synthesis of LaFeO3 via sol-gel route, Ceram. Int. 37 (2011) 1203–1207. R.Z. Hou, P. Ferreira, P.M. Vilarinho, A facil route for synthesis of mesoporous barium titanate crystallites, Microporous Mesoporous Mater. 110 (2008) 392–396. K. Kleveland, M.A. Einarsrud, T. Grande, Sintering of LaCoO3 based ceramics, J. Eur. Ceram. Soc. 20 (2000) 185–193. M.A. Peña, J.L.G. Fierro, Chemical structures and performance of perovskite oxides, Chem. Rev. 101 (2001) 1981–2017. A.V. Salker, N.J. Choi, J.H. Kwak, B.S. Joo, D.D. Lee, Thick films of In, Bi and Pd metal oxides impregnated in LaCoO3 perovskite as carbon monoxide sensor, Sens. Actuat. B 106 (2005) 461–467. L. Jingbo, L. Wenchao, Z. Yanxi, W. Zhimin, Preparation and characterization of Li þ -modified CaxPb1  xTiO3 film for humidity sensor, Sens. Actuators B 75 (2001) 11–17. M.C. Carotta, G. Martinelli, Y. Sadaoka, P. Nunziante, E. Traversa, Gas-sensitive electrical properties of perovskite-type SmFeO3 thick films, Sens. Actuators B 48 (1998) 270–276. M.C. Carotta, G. Martinelli, L. Crema, C. Malagu, M. Merli, G. Ghitti, E. Traversa, Nanostructured thick-film gas sensors for atmospheric pollutant monitoring: quantitative analysis on field tests, Sens. Actuators B 76 (2001) 336–342. J.W. Yoon, M.L. Grilli, E. Di-Bartolomeo, R. Polini, E. Traversa, The NO2 response of solid electrolyte sensor made using nano-sized LaFeO3 electrodes, Sens. Actuators B 76 (2001) 483–488. P. Song, Q. Wang, Z. Zhang, Z. Yang, Synthesis and Gas sensing properties of biomorphic LaFeO3 Hollow Fibers templated from Cotton, Sens. Actuators B 147 (2010) 248–254. X. Chu, S. Zhou, W. Zhang, H. Shui, Trimethylamine sensing properties of nano-LaFeO3 prepared using solid-state reaction in the presence of PEG400, Mater. Sci. Eng. B 164 (2009) 65–69. I. Lázaro, N. Martínez-Medina, I. Rodríguez, I. González, The use of carbon paste electrodes with non-conducting binder for the study of minerals: Chalcopyrite, Hydrometallurgy 38 (1995) 277–287. H. Gómez, J.L. González, G.A. Torres, J. Rodríguez, A. Maldonado, M.L. Olvera, D. R. Acosta, M. Avendaño, L. Castañeda, Chromium and ruthenium-doped zinc oxide thin films for propane sensing applications, Sensors 13 (2013) 3432–3444. W.Y. Lee, H.J. Yun, J.W. Yoon, Characterization and magnetic properties of LaFeO3 nanofibers synthesized by electrospinning, J. Alloy. Compd. 583 (2014) 320–324. S.M. Selbach, J.R. Tolchard, A. Fossdal, T. Grande, Non-linear thermal evolution of the crystal structure and phase transitions of LaFeO3 investigated by high temperature X-ray diffraction, J. Solid State Chem. 196 (2012) 249–254. T. Liu, Y. Xu, Synthesis of nanocrystalline LaFeO3 powders via glucose sol–gel route, Mater. Chem. Phys. 129 (2011) 1047–1050.

Please cite this article as: L. Gildo-Ortiz, et al., Synthesis, characterization and sensitivity tests of perovskite-type LaFeO3 nanoparticles in CO and propane atmospheres, Ceramics International (2016), http://dx.doi.org/10.1016/j.ceramint.2016.09.027i

L. Gildo-Ortiz et al. / Ceramics International ∎ (∎∎∎∎) ∎∎∎–∎∎∎ [39] G. Korotcenkov, Metal oxides for solid-state gas sensors: what determines our choice? Mater. Sci. Eng. B 139 (2007) 1–23. [40] S.R. Hosseini, J.B. Raoof, S. Ghasemi, Z. Gholami, Synthesis of Pt–Cu/poly (oAnisidine) nanocomposite onto carbon paste electrode and its application for methanol oxidation, Int. J. Hydrog. Energy 40 (2015) 292–302. [41] R.J. Voorhoeve, D.W. Johnson, J.P. Remeika, P.K. Gallagher, Perovskite oxides: material science in catalysis, Science 195 (1997) 827–833. [42] V.V. Gorbunov, A.A. Shidlovskii, L.F. Shmagin, Combustion of transition-metal ethylenediamine nitrates, Combust, Explos. Shock 19 (1983) 172–173. [43] L. Gildo, H. Guillén, J. Santoyo, M.L. Olvera, T.V.K. Karthik, E. Campos, J. Reyes, Low-temperature synthesis and gas sensitivity of perovskite-type LaCoO3 nanoparticles, J. Nanomater. 2014 (2014) 8. [44] A. Guillén, V.M. Rodríguez, M. Flores, O. Blanco, J. Reyes, L. Gildo, H. Guillén, Dynamic response of CoSb2O6 trirutile-type oxides in a CO2 atmosphere at low-temperatures, Sensors 2014 (2014) 15802–15814. [45] X. Wang, Y. Li, Solution-based synthetic strategies for 1-D nanostructures, Inorg. Chem. 45 (2006) 7522–7534. [46] V.K. LaMer, R.H. Dinegar, Theory, production and mechanism of formation of monodispersed hydrosols, J. Am. Chem. Soc. 72 (1950) 4847–4854. [47] P. Tang, Y. Tong, H. Chen, F. Cao, G. Pan, Microwave-assisted synthesis of

[48]

[49]

[50] [51] [52] [53]

[54]

7

nanoparticulate perovskite LaFeO3 as a high active visible-light photocatalyst, Curr. Appl. Phys. 13 (2013) 340–343. A.H. Lu, E. Salabas, F. Schuth, Magnetic nanoparticles: synthesis, protection, functionalization, and application, Angew. Chem. Int. Ed. 46 (2007) 1222–1243. H. Guillén, L. Gildo, M.L. Olvera, J. Santoyo, V.M. Rodríguez, A. Guillén, J. Reyes, Sensitivity of mesoporous CoSb2O6 nanoparticles to gaseous CO and C3H8 at low temperatures, J. Nanomater. 2015 (2015) 9. G.F. Fine, L.M. Cavanagh, A. Afonja, R. Binions, Metal oxide semi-conductor gas sensors in environmental monitoring, Sensors 10 (2010) 5469–5502. M. Siemons, U. Simon, High throughput screening of the sensing properties of doped SmFeO3, Solid State Phenom. 128 (2007) 225–236. S.C. Chang, Oxygen chemisorption on tin oxide: correlation between electrical conductivity and EPR measurements, J. Vac. Sci. Technol. 17 (1980) 366–369. H. Guillén, V.M. Rodríguez, J.T. Guillén, J. Reyes, L. Gildo, M. Flores, M.L. Olvera, J. Santoyo, CO and C3H8 sensitivity behavior of zinc antimonate prepared by a microwave-assisted solution method, J. Nanomater. 2015 (2015) 8. J.W. Fergus, Perovskite oxides for semiconductor-based gas sensors, Sens. Actuators B 123 (2007) 1169–1179.

Please cite this article as: L. Gildo-Ortiz, et al., Synthesis, characterization and sensitivity tests of perovskite-type LaFeO3 nanoparticles in CO and propane atmospheres, Ceramics International (2016), http://dx.doi.org/10.1016/j.ceramint.2016.09.027i