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Zirconia- and hafnia-based thin films have attracted tremendous attention in the past decade because of their unexpected ferroelectric behavior at the nanoscale, which enables the downscaling of ferroelectric devices. The present work reports an unprecedented ferroelectric rhombohedral phase of ZrO2 that can be achieved in thin films grown directly on (111)-Nb:SrTiO3 substrates by ion-beam sputtering. Structural and ferroelectric characterizations reveal (111)-oriented ZrO2 films under epitaxial compressive strain exhibiting switchable ferroelectric polarization of about 20.2 μC/cm2 with a coercive field of 1.5 MV/cm. Moreover, the time-dependent polarization reversal characteristics of Nb:SrTiO3/ZrO2/Au film capacitors exhibit typical bell-shaped curve features associated with the ferroelectric domain reversal and agree well with the nucleation limited switching (NLS) model. The polarization-electric field hysteresis loops point to an activation field comparable to the coercive field. Interestingly, the studied films show ferroelectric behavior per se, without the need to apply the wake-up cycle found in the orthorhombic phase of ZrO2. Overall, the rhombohedral ferroelectric ZrO2 films present technological advantages over the previously studied zirconia- and hafnia-based thin films and may be attractive for nanoscale ferroelectric devices. © 2021 American Chemical Society. This work was supported by (i) the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding Contract UIDB/04650/2020 (ii) DST-SERB, Government of India, through Grant ECR/2017/00006, (iii) Project NECL - NORTE-01-0145-FEDER-022096 and Project UID/NAN/50024/2019. This work was also developed within the scope of the project CICECO-Aveiro Institute of Materials, refs UIDB/50011/2020 and UIDP/50011/2020, financed by national funds through the Portuguese Foundation for Science and Technology/MCTES. R.F.N., M.C.I,. and C.G. acknowledge the financial support from the Romanian Ministry of Education and Research within the project PN-III-P4-ID-PCCF2016-0047, contract 16/2018. Work at LIST was supported by the Luxembourg National Research Fund through projects PRIDE/15/10935404 “MASSENA” (S.D.) and INTER/ANR/16/11562984 “EXPAND” (H.A. and J.Í.). The authors acknowledge the CERIC–ERIC Consortium for access to experimental facilities and financial support under proposal 20192055. The authors also thank José Santos for technical support in the Thin Film Laboratory at CF-UM-UP. The equipment of the Ural Center for Shared Use “modern nanotechnology” Ural Federal University (Reg. No. 2968) was used with the financial support of the Ministry of Science and Higher Education of the RF (Project No. 075-15-2021-677).

International audience; Perovskite oxyhydride SrVO2H (V3+, d2) is a Mott insulator with a strong two-dimensional correlation due to anion ordering. In this study, we attempted electron doping by aliovalent substitution. Although Sr1-xLaxVO3 thin films (x ≤ 0.4) on a SrTiO3 substrate were topochemically reduced using CaH2, vanadium of the reduced films retained the trivalent state. Combined with the results of secondary ion mass spectroscopy, we conclude that Sr1-xLaxVO2+xH1-x is obtained, where the apical oxygen site is partially replaced by hydride anions. First-principles theoretical calculations highlight the role played by compressive biaxial strain in stabilizing the charge-compensated Sr1-xLaxVO2+xH1-x phase, rather than the electron-doped Sr1-xLaxVO2H. The present study demonstrates that topochemical reactions combined with substrate strain provide various opportunities to widen the compositional space in mixed-anion compounds. ©

Modulation of the grain boundary properties in thermoelectric materials that have thermally activated electrical conductivity is crucial in order to achieve high performance at low temperatures. In this work, we show directly that the modulation of the potential barrier at the grain boundaries in perovskite SrTiO3 changes the low-temperature dependency of the bulk material's electrical conductivity. By sintering samples in a reducing environment of increasing strength, we produced La0.08Sr0.9TiO3 (LSTO) ceramics that gradually change their electrical conductivity behavior from thermally activated to single-crystal-like, with only minor variations in the Seebeck coefficient. Imaging of the surface potential by Kelvin probe force microscopy found lower potential barriers at the grain boundaries in the LSTO samples that had been processed in the more reducing environments. A theoretical model using the band offset at the grain boundary to represent the potential barrier agreed well with the measured grain boundary potential dependency of conductivity. The present work showed an order of magnitude enhancement in electrical conductivity (from 85 to 1287 S cm(-1)) and power factor (from 143 to 1745 mu W m(-1) K-2) at 330 K by this modulation of charge transport at grain boundaries. This significant reduction in the impact of grain boundaries on charge transport in SrTiO3 provides an opportunity to achieve the ultimate "phonon glass electron crystal" by appropriate experimental design and processing.

We present a theoretical study of the effect of electron-electron interactions and Sr doping on the electronic structure of infinite-layer (Nd,Sr)NiO$_2$ using the density functional+dynamical mean-field theory approach. In particular, we explore the impact of epitaxial compressive strain that experience (Nd,Sr)NiO$_2$ films on the electronic properties, magnetic correlations, and exchange couplings. Our results reveal the crucial importance of orbital-dependent correlation effects in the Ni $3d$ shell of Sr-doped NdNiO$_2$. Upon doping with Sr, it undergoes a Lifshitz transition which is accompanied by a reconstruction of magnetic correlations: For Sr $x0.2$ the $C$-type $(110)$ AFM sets in the unstrained (Nd,Sr)NiO$_2$, with a highly frustrated region at $x \simeq 0.2$, all within DFT+DMFT at $T=290$ K. Our results for the Néel AFM at Sr $x=0$ suggest that AFM NdNiO$_2$ appears at the verge of a Mott-Hubbard transition, providing a plausible explanation for the experimentally observed weakly insulating behavior of NdNiO$_2$ for Sr $x, 11 pages, 9 figures; the crystal structure used is under question; this may affect the result

One of the hallmarks of the Berezinskii-Kosterlitz-Thouless (BKT) transition in two-dimensional superconductors is the universal jump of the superfluid density that can be indirectly probed via the nonlinear exponent of the current-voltage I-V characteristics. Here, we compare the experimental measurements of I-V characteristics in two cases, namely NbN thin films and SrTiO3-based interfaces. While the former display a paradigmatic example of BKT-like nonlinear effects, the latter do not seem to justify a BKT analysis. Rather, the observed I-V characteristics can be well reproduced theoretically by modeling the effect of mesoscopic inhomogeneity of the superconducting state. Our results offer an alternative perspective on the spontaneous fragmentation of the superconducting background in confined two-dimensional systems.

Funding acknowledgement: SCOTAS FCHJU 256730 A lanthanum and calcium co-doped A-site deficient strontium titanate (LSCTA–) was used as alternative anode material in Solid Oxide Fuel Cells (SOFC) with an active area of 100 cm2. Cell performance was tested in both short (5 cell) stack configuration, as well as a full HEXIS Galileo system (nominally 1 kW AC). Impregnation with various electrocatalysts, such as nickel and ceria, yielded promising fuel cell performance at this scale. The system test initially produced 70% of the nominal output power and is to the authors' knowledge the first all-oxide SOFC test on this scale. The strontium titanate backbone provides sufficient electronic conductivity to ensure acceptable ohmic losses. Power densities up to 200 mA cm−2 could be obtained at 900 °C, which compares well with Ni-cermet based anodes. Degradation is however severe at 900 °C, due to impregnate coarsening, but operation at 850 °C minimizes this effect. Short stacks could be stably operated for 1,600 hours with an output power of 100 mA cm−2. Stacks are redox stable, but currently not sulphur tolerant. Postprint

An investigation of the optical properties and band structures for the conventional and Fibonacci photonic crystals (PCs) based on SrTiO3 and Sb2Te3 is made in the present research. Here, we use one-dimensional SrTiO3- and Sb2Te3-based layers. We have theoretically calculated the photonic band structure and transmission spectra of SrTiO3- and Sb2Te3-based PC superlattices. The position of minima in the transmission spectrum correlates with the gaps obtained in the calculation. The intensity of the transmission depths is more intense in the case of higher refractive index contrast between the layers. This work is supported by the projects DPTHAMIT, DPT-FOTON, NATO-SET-193 and TUBITAK under Project Nos., 113E331, 109A015, 109E301. One of the authors (Ekmel Ozbay) also acknowledges partial support from the Turkish Academy of Sciences.

Understanding of structural, optical, and electrical properties of thin films are very important for a reliable device performance. In the present work, the effect of postdeposition annealing on stoichiometric SrTiO3 (STO) thin films grown by radio frequency magnetron sputtering at room temperature on p-type Si (100) and quartz substrates were studied. Highly transparent and well adhered thin films were obtained in visible and near infrared regions. As-deposited films were amorphous, while nanocrystalline and polycrystalline phases of the STO thin films formed as a function of annealing temperature. Films annealed at 300 degrees C showed nanocrystallinity with some amorphous phase. Crystallization started after 15 min annealing at 700 degrees C, and further improved for films annealed at 800 degrees C. However, crystallinity reduced for films which were annealed at 900 degrees C. The optical and electrical properties of STO thin films affected by postdeposition annealing at 800 degrees C: E-g values decreased from 4.50 to 4.18 eV, n(lambda) values (at 550 nm) increased from 1.81 to 2.16. The surface roughness increased with the annealing temperature due to the increased crystallite size, densification and following void formation which can be seen from the scanning electron microscopy images. The highest dielectric constants (46 at 100 kHz) observed for films annealed at 800 degrees C; however, it was lower for 300 degrees C annealed (25 at 100 kHz) and as-deposited (7 at 100 kHz) STO films having similar to 80 nm thickness. (C) 2017 American Vacuum Society.

Nas últimas décadas, o consumo de dispositivos eletrônicos e a alta demanda por armazenamento de dados tem mostrado grandes oportunidades para a criação de novas tecnologias que garantam as necessidades mundiais na área de computação e desenvolvimento. Alguns materiais multiferroicos tem sido amplamente estudados e o BiFeO3, considerado o único material multiferroico em temperatura ambiente, ganhou destaque como candidato para produção de dispositivos lógicos e de memória. O uso de técnicas de crescimento como a deposição por laser pulsado permitiu a produção de filmes finos de BiFeO3 com elevado controle de qualidade. Heteroestruturas de filmes multiferroicos de BiFeO3 e LaBiFeO3 foram crescidas com diferentes espessuras sobre substratos de SrTiO3(100), DyScO3(110) e SrTiO3/Si(100) para avaliação e teste de suas propriedades elétricas e magnéticas. Filmes ferromagnéticos de Co0,9Fe0,1 foram depositados por sputtering sobre os filmes multiferroicos para avaliação da interação interfacial entre ordenamentos magnéticos. Técnicas como fotolitografia foram utilizadas para padronização de microdispositivos gravados sobre as amostras. Tanto os filmes finos de BiFeO3 como os de LaBiFeO3 foram crescidos epitaxialmente sobre os substratos já cobertos com uma camada buffer de SrRuO3 usado como contato elétrico inferior. A estrutura cristalina romboédrica das ferritas de bismuto foi confirmada pelos dados de difração de raios X, bem como a manutenção de tensão estrutural causada pela rede cristalina do substrato para amostras de 20 nm. Os valores de coeficiente do tensor piezelétrico d33 foram da ordem de 0,15 V (∼ 60 kV.cm-2) para amostras com 20 nm de espessura enquanto que os valores de voltagem coerciva para as análises de histerese elétrica foram da ordem de 0,5 V para as mesmas amostras. A relação de coercividade elétrica com a espessura corresponde ao perfil encontrado na literatura pela relação E≈d-2/3. As amostras de CoFe/BFO e CoFe/LBFO depositadas em diferentes substratos apresentam acoplamento interfacial entre ordenamento ferromagnético e antiferromagnético com momento ferromagnético de rede. For the last few decades, the consumption of electronic devices and the high demand for data storage have shown great opportunities to create modern technologies that assure the worldwide needs in computing and development. Some multiferroic materials have been extensively studied and BiFeO3, considered the only multiferroic material at room temperature, has received attention as a candidate to produce logic and memory devices. The use of growth techniques such as pulsed laser deposition allowed the production of thin films of BiFeO3 with high quality control. Multiferroic film heterostructures of BiFeO3 and LaBiFeO3 were grown with different thicknesses on SrTiO3 (100), DyScO3 (110) and SrTiO3/Si (100) substrates to evaluate and test their electrical and magnetic properties. The allow Co0.9Fe0.1 ferromagnetic films were deposited by sputtering on the multiferroic films to evaluate the interfacial interaction between magnetic ordering. Techniques such as photolithography were used to pattern microdevices on the samples. Both the BiFeO3 and LaBiFeO3 thin films were grown epitaxially on the substrates already covered with a SrRuO3 buffer layer used as the lower electrical contact. The rhombohedral crystalline structure of the bismuth ferrites was confirmed by the X-ray diffraction data as well as the strain maintenance caused by the crystal lattice of the substrate for 20 nm samples. The coefficient values of the piezoelectric tensor d33 were around 0.15 V (∼ 60 kV.cm-2) for 20 nm thick samples whereas the coercive voltage values for the electrical hysteresis analyzes were about 0.5 V for the same samples. The relation between electric coercivity and the thickness corresponds to the profile found in the literature by the relation E≈d-2/3. The samples of CoFe/BFO and CoFe/LBFO deposited in different substrates present interfacial coupling between ferromagnetic and antiferromagnetic arrangement with net ferromagnetic moment.

At interfaces between complex oxides it is possible to generate electronic systems with unusual electronic properties, which are not present in the isolated oxides. One important example is the appearance of superconductivity at the interface between insulating oxides, although, until now, with very low Tc. We report the occurrence of high Tc superconductivity in the bilayer CaCuO2/SrTiO3, where both the constituent oxides are insulating. In order to obtain a superconducting state, the CaCuO2/SrTiO3 interface must be realized between the Ca plane of CaCuO2 and the TiO2 plane of SrTiO3. Only in this case extra oxygen ions can be incorporated in the interface Ca plane, acting as apical oxygen for Cu and providing holes to the CuO2 planes. A detailed hole doping spatial profile has been obtained by STEM/EELS at the O K-edge, clearly showing that the (super)conductivity is confined to about 1-2 CaCuO2 unit cells close to the interface with SrTiO3. The results obtained for the CaCuO2/SrTiO3 interface can be extended to multilayered high Tc cuprates, contributing to explain the dependence of Tc on the number of CuO2 planes in these systems., 14 pages, 4 figures

For materials based on ferrites and manganites with DD degrees(2+) and D'D degrees(2+) cations substituted into D sublattice, the functional properties are studied and the prospects as electrode materials for solid-oxide fuel cells are assessed. The electronic conductivity of materials based on La(0.5)A(0.5)Mn(0.5)Ti(0.5)O(3-delta) is shown to decrease with the increase in the ionic radius of alkali-earth substituent; however, for La0.5D'D degrees 0.5Mn0.5Ti0.5O3-delta and La0.5D'D degrees 0.5Fe0.5Ti0.5O3-delta, the appearance of n-conduction is observed during reduction, which may provide adequate conductivity under anodic conditions. Under the conditions of fuel cell operation, the thermal expansion coefficients of these materials are (13.0-13.5) x 10(-6) K-1. The thermal and chemical expansion increases with the increase in the radius of alkali-earth cation; the latter value does not exceed 0.2%, which is acceptable for preparation of electronic layers. The transition of oxygen through membranes based on materials studied is determined to the large extent by the kinetics of surface exchange which depends on the rate of delivery of oxygen vacancies to the surface. Doping of ferrites with chromium or titanium decreases the electronic and ionic conductivity; however, the presence of substituents in D' sublattice makes it possible to stabilize the perovskite phase in a wide range of NEuro(D-2), decrease the thermal and chemical expansion, and prevent to the large extent the ordering of oxygen vacancies, which allows one to consider these materials as the candidates for electrodes in symmetrical solid-oxide fuel cells.

Modified strontium titanates have received much attention recently for their potential as anode material in solid oxide fuel cells (SOFC). Their inherent redox stability and superior tolerance to sulphur poisoning and coking as compared to Ni based cermet anodes could improve durability of SOFC systems dramatically. Various substitution strategies can be deployed to optimise materials properties in these strontium titanates, such as electronic conductivity, electrocatalytic activity, chemical stability and sinterability, and thus mechanical strength. Substitution strategies not only cover choice and amount of substituent, but also perovskite defect chemistry, distinguishing between A-site deficiency (A1-xBO3) and cation-stoichiometry (ABO3+δ). Literature suggests distinct differences in the materials properties between the latter two compositional approaches. After discussing the defect chemistry of modified strontium titanates, this paper reviews three different A-site deficient donor (La, Y, Nb) substituted strontium titanates for their electrical behaviour and fuel cell performance. Promising performances in both electrolyte as well as anode supported cell designs have been obtained, when using hydrogen as fuel. Performances are retained after numerous redox cycles. Long term stability in sulphur and carbon containing fuels still needs to be explored in greater detail. This journal is

SrTiO3 particle-composed films were grown on Si substrates via picosecond ultrafast pulsed laser deposition. We have investigated the effect of laser pulse repetition rate (0.2-8.2 MHz) and fluence (0.079-1.57 J cm-2) on the morphology, crystallinity and stoichiometry of the films. X-ray diffraction, energy dispersive X-ray spectroscopy and Rutherford backscattering spectroscopy measurements demonstrated that the as-grown films were nearly stoichiometric and composed of large particles when a pulse repetition rate of 0.2 MHz was employed. However, at the higher repetition rate of 8.2 MHz the particle size decreased and the stoichiometry was altered. Finally, we attribute the formation of micron-size particle-composed films to the slow translation speed in relation to the high pulse repetition rates (kHz-MHz regime). © 2014 Elsevier B.V. All rights reserved. 336 278 282 278-282

Cobalt-substituted SrTiO3 films (SrTi0.70Co0.30O3-δ) were grown on SrTiO3 substrates using pulsed laser deposition under oxygen pressures ranging from 1 μTorr to 20 mTorr. The effect of oxygen pressure on structural, magnetic, optical, and magneto-optical properties of the films was investigated. The film grown at 3 μTorr has the highest Faraday rotation (FR) and magnetic saturation moment (Ms). Increasing oxygen pressure during growth reduced Ms, FR and optical absorption in the nearinfrared. This trend is attributed to decreasing Co2+ ion concentration and oxygen vacancy concentration with higher oxygen partial pressure during growth. © 2015 Optical Society of America.

This work investigates the impact of the exposition to SOFC anode operating conditions on SrTiO3-based compounds, with A-site or B-site substitution: 10 at.% lanthanum or 20 at.% niobium, respectively. Structural and surface stability of the materials after the reaction was examined (post-mortem analysis) using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). These techniques have allowed us to obtain bulk and surface information of the samples which will have a crucial relevance in revealing possible modifications accomplished during system operation. These modifications could play an important role in the degradation of the cell. Structural analysis of materials before and after reduction did not show the formation of secondary phases, indicating a good stability of their crystalline structures for both samples under the conditions employed. In turn, surface study by means of XPS evidenced a surface enrichment in strontium oxide species for raw samples just after annealing. Nevertheless, exposure to the reducing environment caused an accumulation on the surface of the cations that occupy B positions in the perovskite structure oxides. At the same time, lanthanum segregation to the surface after the exposition to the reducing treatment was revealed as well. Achieved identification of the cationic diffusion processes that happened throughout cell operation will help us to understand and eventually minimize the degradation of the anode materials.

In this work we have systematically investigated the evolution of structure and stoichiometry in SrCuO2 films grown on TiO2-terminated SrTiO3 substrates as a function of the substrate temperature. Depending on the growth temperature SrCuO2/SrTiO3 films can exhibit either a pure tetragonal high-pressure phase, or a pure orthorhombic low-pressure phase, or a mixed phase. Our results indicate that at low substrate temperatures the non-equilibrium state of the growth process is responsible for the stabilization of the metastable tetragonal high-pressure structure in SrCuO2 thin films grown on (0 0 1) SrTiO3 substrates, whose lattice matches the metastable structure. In addition, at higher substrate temperatures thermodynamics become dominant over other factors and the SrCuO2 thin films are stabilized in the thermodynamically stable orthorhombic phase. © 2014 Elsevier B.V. All rights reserved. 320 852 857 852-857

In this article, we present novel sample preparation methods using a helium ion microscope (HIM). We report the possibility of reshaping, at room temperature, thin metal lines on an electron-transparent membrane: A set of platinum bridges with standard geometry (300 × 200 × 15 nm) was modified at room temperature into different shapes using focused helium (He)-ion beam. Also the applicability of the HIM as a tool for precise modification of silicon (Si) and strontium titanate (SrTiO3) lamellae is shown and discussed. We demonstrated that in situ heating (e.g., at 600 °C) of the samples during He-beam illumination by use of a specially developed heating stage enables production of thin Si and SrTiO3 samples without significant artifacts. The quality of such cuts was inspected by transmission electron microscopy with high-resolution imaging, and the diffraction patterns were analyzed. Copyright © Materials Research Society 2013.

In this article, we present novel sample preparation methods using a helium ion microscope (HIM). We report the possibility of reshaping, at room temperature, thin metal lines on an electron-transparent membrane: A set of platinum bridges with standard geometry (300 × 200 × 15 nm) was modified at room temperature into different shapes using focused helium (He)-ion beam. Also the applicability of the HIM as a tool for precise modification of silicon (Si) and strontium titanate (SrTiO3) lamellae is shown and discussed. We demonstrated that in situ heating (e.g., at 600 °C) of the samples during He-beam illumination by use of a specially developed heating stage enables production of thin Si and SrTiO3 samples without significant artifacts. The quality of such cuts was inspected by transmission electron microscopy with high-resolution imaging, and the diffraction patterns were analyzed. Copyright © Materials Research Society 2013.

In the present study stoichiometric, b-axis oriented La5Ca 9Cu24O41 thin films were grown by pulsed laser deposition on (1 1 0) SrTiO3 substrates in the temperature range 600-750 °C. High resolution transmission electron microscopy was employed to investigate the growth mechanism and the epitaxial relationship between the SrTiO3 substrates and the La5Ca9Cu 24O41 films grown at 700 °C. The 3-ω method was used to measure the cross-plane thermal conductivity of La5Ca 9Cu24O41 films in the temperature range 50-350 K. The observed glass-like behavior is attributed to atomic-scale defects, grain boundaries and an interfacial layer formed between film and substrate. © 2011 Elsevier B.V. All rights reserved. 520 4613 4616 4613-4616

Composições cerâmicas de CaxSr1-xTi1-yFeyO3-δ, x = 0, 0,5 e 1,0, y = 0 e 0,35, foram preparadas por meio de síntese reativa de CaCO3, SrCO3, TiO2 e Fe2O3 e pela técnica dos precursores poliméricos. Os pós-cerâmicos foram avaliados por meio de análise térmica (termogravimétrica e térmica diferencial), difração de raios X e microscopia eletrônica de varredura. Compactos cerâmicos sinterizados foram analisados por difração de raios X, microscopia eletrônica de varredura, microscopia de varredura por sonda e espectroscopia de impedância. A força eletromotriz gerada entre duas faces paralelas de amostras cilíndricas foi monitorada na faixa de temperatura 600 - 1100 oC para pressão parcial de oxigênio de ~50 ppm, utilizando-se uma bomba eletroquímica de oxigênio com transdutores de zircônia estabilizada com ítria. Foram refinadas, por meio de análise de Rietveld as estruturas cristalinas determinadas na análise por difração de raios X: perovskita cúbica (x = 0) e perovskita ortorrômbica (x 0). A condutividade elétrica foi analisada por medidas de espectroscopia de impedância na faixa de freqüências 5 Hz-13 MHz da temperatura ambiente até ~200 C. A deconvolução dos diagramas de impedância [-Z\"() x Z\'()] na faixa de temperaturas 300 < T(K) < 500 mostra dois semicírculos atribuídos às contribuições intragranular (grãos) e intergranular (contornos de grão) à resistividade elétrica. Os compactos sinterizado utilizando pós preparados pela síntese de estado sólido apresentam valores de resistividade intergranular e intragranular maiores que os compactos preparados com pós obtidos pela síntese química. O sinal elétrico (força eletromotriz) gerado sob exposição a oxigênio mostra que esses compostos podem ser utilizados em dispositivos sensores de oxigênio entre 600 e 1100C. Análises topográficas em microscópio de varredura por sonda em superfícies polidas e atacadas termicamente mostram detalhes morfológicos dos grãos, permitindo concluir que compactos sinterizados preparados com pós obtidos pela rota química são menos porosos que os preparados com pós obtidos pela rota convencional de síntese de estado sólido. Estes resultados estão de acordo com os resultados de medidas de espectroscopia de impedância. CaxSr1-xTi1-yFeyO3-δ, x = 0, 0.5 and 1.0, y = 0 and 0.35, ceramic compounds were synthesized by reactive solid state synthesis of CaCO3, SrCO3, TiO2 and Fe2O3, and by the polymeric precursor technique. The ceramic powders were evaluated by thermogravimetry and differential thermal analysis, X-ray diffraction and scanning electron microscopy. Sintered ceramic pellets were analyzed by X-ray diffraction, scanning electron microscopy, scanning probe microscopy and impedance spectroscopy. The electromotive force resulting from the exposing the pellets to partial pressure de oxygen in the ~50 ppm in the 600-1100 oC range was monitored using an experimental setup consisting of an oxygen electrochemical pump with yttria-stabilized zirconia transducer and sensor. Rietveld analysis of the X-ray data allowed for determining the crystalline structures: cubic perovskite (y = 0) and orthorhombic perovskite (y 0). The electrical conductivity was determined by the two probe impedance spectroscopy measurements in the 5 Hz-13 MHz frequency range from room temperature to approximately 200 C. The deconvolution of the [-Z\"() x Z\'()] impedance diagrams in the 300 < T(K) < 500 range shows two semicircles due to intragranular (bulk) and intergranular (grain boundary) contributions to the electrical resistivity. Sintered pellets using powders prepared by the ceramic route present higher inter- and intragranular resistivity values than pellets prepared with chemically synthesized powders. The emf signal under exposure oxygen shows that these compounds may be used in oxygen sensing devices in the 600 - 1100 C range. Scanning probe microscopy topographic analysis of the polished and thermally etched surfaces of the pellets gave details of grain morphology, showing that pellets prepared with powders synthesized by the chemical route are less porous than the ones obtained by the ceramic route. These results are in agreement with the impedance spectroscopy results.

Superlattices consist of two ferromagnets La0.7Sr 0.3MnO3 (LSMO) and SrRuO3 (SRO) were grown in (110)-orientation on SrTiO3 (STO) substrates. The x-ray diffraction and Raman spectra of these superlattices show the presence of in-plane compressive strain and orthorhombic structure of less than 4 u.c. thick LSMO spacer, respectively. Magnetic measurements reveal several features including reduced magnetization, enhanced coercivity, antiferromagnetic coupling, and switching from antiferromagnetic to ferromagnetic coupling with magnetic field orientations. These magnetic properties are explained by the observed orthorhombic structure of spacer LSMO in Raman scattering which occurs due to the modification in the stereochemistry of Mn at the interfaces of SRO and LSMO. � 2014 AIP Publishing LLC.