CEMAD - Caracterització elèctrica de materials i dispositiushttp://hdl.handle.net/2117/3882021-05-09T14:42:53Z2021-05-09T14:42:53Z((R)-(-)-3-Hydroxyquinuclidium)[FeCl4]; a plastic hybrid compound with chirality, ferroelectricity and long range magnetic orderingGonzález Izquiero, PalmerinaFabelo, OscarCanadillas Delgado, LauraBeobide, GarikoitzVallcorba, OriolSalgado Beceiro, JorgeSánchez Andújar, ManuelMartin, CarmenRuiz Fuentes, JavierGarcía García, José EduardoFernández Díaz, Maria Teresade Pedro, Imanolhttp://hdl.handle.net/2117/3431752021-04-06T14:50:27Z2021-04-06T14:42:56Z((R)-(-)-3-Hydroxyquinuclidium)[FeCl4]; a plastic hybrid compound with chirality, ferroelectricity and long range magnetic ordering
González Izquiero, Palmerina; Fabelo, Oscar; Canadillas Delgado, Laura; Beobide, Garikoitz; Vallcorba, Oriol; Salgado Beceiro, Jorge; Sánchez Andújar, Manuel; Martin, Carmen; Ruiz Fuentes, Javier; García García, José Eduardo; Fernández Díaz, Maria Teresa; de Pedro, Imanol
Quinuclidinium salts and their derivatives are now in the focus of materials science as building units of multifunctional materials. Their properties can be easily switchable, allowing their use in a wide range of physical applications. One type of these kinds of materials, the homochiral hybrid halometallate ferroelectric compounds, is not well understood. In this work, (R)-(-)-3-quinuclidinol hydrochloride was used in the synthesis of ((R)-(-)-3-hydroxyquinuclidium)[FeCl4]. The use of this enantiomeric cation forces crystallographic non-centrosymmetry, which was confirmed by polarimetry and circular dichroism spectroscopy. We studied the physical properties of this compound at different temperatures by single crystal, synchrotron and neutron powder X-ray diffraction, which showed a rich series of structural and magnetic phase transitions. From synchrotron powder X-ray diffraction data, a plastic phase was observed above 370 K (phase I). Between 370 K and ca. 310 K, an intermediate polar phase was detected, solved in a non-centrosymmetric polar space group (C2) (phase II). Below ca. 310 K, the compound crystallizes in the triclinic P1 non-centrosymmetric space group (phase III) which is maintained down to 4 K, followed by phase IV, which shows tridimensional magnetic ordering. The temperature evolution of the neutron diffraction data shows the appearance of new reflections below 4 K. These reflections can be indexed to a commensurate propagation vector k = (0, 0, ½). The magnetic structure below TN was solved in the Ps1 Shubnikov space group, which gives rise to an antiferromagnetic structure, compatible with the magnetometry measurements. Near room temperature, the crystal phase transition is associated with a dielectric change. In particular, the phase transition between phase III (S.G.:P1) and phase II (S.G.:C2) involves an increase of symmetry between two non-centrosymmetric space groups. Therefore, it allows, by symmetry, the emergence of ferroelectric and ferroelastic ordering. Piezoresponse force microscopy (PFM) imaging measurements provided evidence for polarization switching and a local ferroelectric behavior of phase III at room temperature. Additionally, the obtained butterfly curve and hysteresis loop by PFM exhibits a low coercive voltage of ~10 V. This value is remarkable, since it approaches those obtained for materials with application in ferroelectric random access memories (FeRAMs).
2021-04-06T14:42:56ZGonzález Izquiero, PalmerinaFabelo, OscarCanadillas Delgado, LauraBeobide, GarikoitzVallcorba, OriolSalgado Beceiro, JorgeSánchez Andújar, ManuelMartin, CarmenRuiz Fuentes, JavierGarcía García, José EduardoFernández Díaz, Maria Teresade Pedro, ImanolQuinuclidinium salts and their derivatives are now in the focus of materials science as building units of multifunctional materials. Their properties can be easily switchable, allowing their use in a wide range of physical applications. One type of these kinds of materials, the homochiral hybrid halometallate ferroelectric compounds, is not well understood. In this work, (R)-(-)-3-quinuclidinol hydrochloride was used in the synthesis of ((R)-(-)-3-hydroxyquinuclidium)[FeCl4]. The use of this enantiomeric cation forces crystallographic non-centrosymmetry, which was confirmed by polarimetry and circular dichroism spectroscopy. We studied the physical properties of this compound at different temperatures by single crystal, synchrotron and neutron powder X-ray diffraction, which showed a rich series of structural and magnetic phase transitions. From synchrotron powder X-ray diffraction data, a plastic phase was observed above 370 K (phase I). Between 370 K and ca. 310 K, an intermediate polar phase was detected, solved in a non-centrosymmetric polar space group (C2) (phase II). Below ca. 310 K, the compound crystallizes in the triclinic P1 non-centrosymmetric space group (phase III) which is maintained down to 4 K, followed by phase IV, which shows tridimensional magnetic ordering. The temperature evolution of the neutron diffraction data shows the appearance of new reflections below 4 K. These reflections can be indexed to a commensurate propagation vector k = (0, 0, ½). The magnetic structure below TN was solved in the Ps1 Shubnikov space group, which gives rise to an antiferromagnetic structure, compatible with the magnetometry measurements. Near room temperature, the crystal phase transition is associated with a dielectric change. In particular, the phase transition between phase III (S.G.:P1) and phase II (S.G.:C2) involves an increase of symmetry between two non-centrosymmetric space groups. Therefore, it allows, by symmetry, the emergence of ferroelectric and ferroelastic ordering. Piezoresponse force microscopy (PFM) imaging measurements provided evidence for polarization switching and a local ferroelectric behavior of phase III at room temperature. Additionally, the obtained butterfly curve and hysteresis loop by PFM exhibits a low coercive voltage of ~10 V. This value is remarkable, since it approaches those obtained for materials with application in ferroelectric random access memories (FeRAMs).Toward a new PTCR material based on the Na2Ti6O13/Na2Ti3O7 systemBasilio, L.A.L.Silva, J.H.L.Xavier, F.Aguilera, LianetGuerrero, FidelAntonelli, EduardoAnglada-Rivera, JoséGarcía García, José EduardoSilva, R.S.Leyet, Yurimilerhttp://hdl.handle.net/2117/3425932021-03-29T01:03:15Z2021-03-26T11:57:40ZToward a new PTCR material based on the Na2Ti6O13/Na2Ti3O7 system
Basilio, L.A.L.; Silva, J.H.L.; Xavier, F.; Aguilera, Lianet; Guerrero, Fidel; Antonelli, Eduardo; Anglada-Rivera, José; García García, José Eduardo; Silva, R.S.; Leyet, Yurimiler
Mixed phases of sodium titanate ceramics are obtained using both conventional and laser sintering methods. It was observed a clear dependence on the structural, microstructural and electrical resistivity with the employed sintering method. The temperature dependence of the resistivity in the ceramics shows an increase of three orders of magnitude in a narrow range of temperatures, thereby indicating a noticeable positive temperature coefficient of resistivity (PTCR) effect. To explain this observed abnormal behavior, a model based on the structure of the Na2Ti6O13/Na2Ti3O7 composite is proposed. A new class of PTCR materials is reported.
2021-03-26T11:57:40ZBasilio, L.A.L.Silva, J.H.L.Xavier, F.Aguilera, LianetGuerrero, FidelAntonelli, EduardoAnglada-Rivera, JoséGarcía García, José EduardoSilva, R.S.Leyet, YurimilerMixed phases of sodium titanate ceramics are obtained using both conventional and laser sintering methods. It was observed a clear dependence on the structural, microstructural and electrical resistivity with the employed sintering method. The temperature dependence of the resistivity in the ceramics shows an increase of three orders of magnitude in a narrow range of temperatures, thereby indicating a noticeable positive temperature coefficient of resistivity (PTCR) effect. To explain this observed abnormal behavior, a model based on the structure of the Na2Ti6O13/Na2Ti3O7 composite is proposed. A new class of PTCR materials is reported.Performance assessment of ultrasonic waves for bubble control in cryogenic fuel tanksSuñol Galofre, Francesc XavierOchoa Guerrero, Diego A.Granados Jiménez, MartaGonzález Cinca, RicardoGarcía García, José Eduardohttp://hdl.handle.net/2117/3349882021-01-17T04:26:00Z2021-01-07T12:32:04ZPerformance assessment of ultrasonic waves for bubble control in cryogenic fuel tanks
Suñol Galofre, Francesc Xavier; Ochoa Guerrero, Diego A.; Granados Jiménez, Marta; González Cinca, Ricardo; García García, José Eduardo
An efficient long-term storage of cryogenic propellants is a challenge for future space exploration missions. The vapour bubbles formed as a result of boil-off in the tank walls can generate foam structures, which could be hazardous in different operations in orbit. A recently proposed approach to control the dynamics of bubbles is based on the generation of an acoustic field by means of a piezoelectric transducer. This technology needs to be validated at cryogenic temperatures in order to be applicable in space. In this perspective, different piezoelectric elements and matching layer materials have been tested at cryogenic temperatures to assess their performance at such environmental conditions. We consider the use of soft PZT piezoceramics coupled with an epoxy resin as the matching layer. Experimental data reveal that epoxy resin-based acoustic matching layers exhibit a linear increase in the transmittance of the acoustic amplitude at cryogenic conditions. The peak-to-peak amplitude increases as temperature decreases up to a factor of 1.6. This result opens the possibility of generating and transmitting acoustic waves at cryogenic temperatures, which could be used in the recently proposed technology to control the dynamics of vapour bubbles in cryogenic fuel tanks.
2021-01-07T12:32:04ZSuñol Galofre, Francesc XavierOchoa Guerrero, Diego A.Granados Jiménez, MartaGonzález Cinca, RicardoGarcía García, José EduardoAn efficient long-term storage of cryogenic propellants is a challenge for future space exploration missions. The vapour bubbles formed as a result of boil-off in the tank walls can generate foam structures, which could be hazardous in different operations in orbit. A recently proposed approach to control the dynamics of bubbles is based on the generation of an acoustic field by means of a piezoelectric transducer. This technology needs to be validated at cryogenic temperatures in order to be applicable in space. In this perspective, different piezoelectric elements and matching layer materials have been tested at cryogenic temperatures to assess their performance at such environmental conditions. We consider the use of soft PZT piezoceramics coupled with an epoxy resin as the matching layer. Experimental data reveal that epoxy resin-based acoustic matching layers exhibit a linear increase in the transmittance of the acoustic amplitude at cryogenic conditions. The peak-to-peak amplitude increases as temperature decreases up to a factor of 1.6. This result opens the possibility of generating and transmitting acoustic waves at cryogenic temperatures, which could be used in the recently proposed technology to control the dynamics of vapour bubbles in cryogenic fuel tanks.Bifurcation analysis in a self-oscillating series resonant converterPonce, EnriqueBenadero García-Morato, LuisEl Aroudi, Abdelalihttp://hdl.handle.net/2117/1831462020-07-23T21:13:13Z2020-04-03T17:26:33ZBifurcation analysis in a self-oscillating series resonant converter
Ponce, Enrique; Benadero García-Morato, Luis; El Aroudi, Abdelali
In this paper, the dynamics of a dc-ac resonant self-oscillating LC series inverter is analyzed from the point of view of piecewise smooth dynamical systems. The system under study is defined by two symmetric configurations and its bifurcation analysis is performed in a one dimensional parameter space. This analysis reveals that a non smooth transition takes place between two strongly different dynamical behaviors. The first one is an oscillating regime, which is the one used in applications and it involves a repetitive switching sequence between the system configurations. This behavior is exhibited whenever the open loop equilibrium corresponding to the system configurations are foci. The second one is a non desired stationary regime corresponding to the equilibrium points of node type whose stable manifolds preclude the appearance of oscillations.
2020-04-03T17:26:33ZPonce, EnriqueBenadero García-Morato, LuisEl Aroudi, AbdelaliIn this paper, the dynamics of a dc-ac resonant self-oscillating LC series inverter is analyzed from the point of view of piecewise smooth dynamical systems. The system under study is defined by two symmetric configurations and its bifurcation analysis is performed in a one dimensional parameter space. This analysis reveals that a non smooth transition takes place between two strongly different dynamical behaviors. The first one is an oscillating regime, which is the one used in applications and it involves a repetitive switching sequence between the system configurations. This behavior is exhibited whenever the open loop equilibrium corresponding to the system configurations are foci. The second one is a non desired stationary regime corresponding to the equilibrium points of node type whose stable manifolds preclude the appearance of oscillations.Polymorphic phase boundary in piezoelectric oxidesGarcía García, José EduardoRubio Marcos, Fernandohttp://hdl.handle.net/2117/1831242020-07-23T20:38:17Z2020-04-03T15:08:44ZPolymorphic phase boundary in piezoelectric oxides
García García, José Eduardo; Rubio Marcos, Fernando
The design of phase boundaries has now become a consolidated strategy to improve the functional properties of piezoelectric oxides because of the unique properties that may be obtained in their vicinity. In particular, polymorphic phase boundaries (PPBs) have attracted significant interest in recent years because they represent a significant breakthrough in terms of enhanced piezoelectric activity of lead-free piezoelectric oxides. PPBs are temperature-driven phase transitions where both intrinsic and extrinsic contributions maximize, thereby enhancing the macroscopic properties of piezoelectric materials. This tutorial discusses potassium–sodium–niobate-based systems as model materials to reveal some of the most relevant advances in the design of PPBs through compositional modifications. We focus on how PPBs can be modulated by engineered doping and also discuss the direct relation between PPBs and the enhancement of piezoelectric activity. Finally, we briefly describe the main experimental techniques for detecting PPBs.
2020-04-03T15:08:44ZGarcía García, José EduardoRubio Marcos, FernandoThe design of phase boundaries has now become a consolidated strategy to improve the functional properties of piezoelectric oxides because of the unique properties that may be obtained in their vicinity. In particular, polymorphic phase boundaries (PPBs) have attracted significant interest in recent years because they represent a significant breakthrough in terms of enhanced piezoelectric activity of lead-free piezoelectric oxides. PPBs are temperature-driven phase transitions where both intrinsic and extrinsic contributions maximize, thereby enhancing the macroscopic properties of piezoelectric materials. This tutorial discusses potassium–sodium–niobate-based systems as model materials to reveal some of the most relevant advances in the design of PPBs through compositional modifications. We focus on how PPBs can be modulated by engineered doping and also discuss the direct relation between PPBs and the enhancement of piezoelectric activity. Finally, we briefly describe the main experimental techniques for detecting PPBs.Performance assessment of ultrasonic waves for bubble control in LOX tanksSuñol Galofre, Francesc XavierOchoa Guerrero, Diego A.Granados, MartaGarcía García, José EduardoGonzález Cinca, Ricardohttp://hdl.handle.net/2117/1829362020-07-23T23:24:11Z2020-04-02T12:07:56ZPerformance assessment of ultrasonic waves for bubble control in LOX tanks
Suñol Galofre, Francesc Xavier; Ochoa Guerrero, Diego A.; Granados, Marta; García García, José Eduardo; González Cinca, Ricardo
2020-04-02T12:07:56ZSuñol Galofre, Francesc XavierOchoa Guerrero, Diego A.Granados, MartaGarcía García, José EduardoGonzález Cinca, RicardoDynamic analysis of self-oscillating H-bridge inverters with state feedbackBenadero García-Morato, LuisTorres Peral, FranciscoPonce Núñez, EnriqueEl Aroudi, Abdelalihttp://hdl.handle.net/2117/1759802021-01-31T01:28:08Z2020-01-28T19:38:52ZDynamic analysis of self-oscillating H-bridge inverters with state feedback
Benadero García-Morato, Luis; Torres Peral, Francisco; Ponce Núñez, Enrique; El Aroudi, Abdelali
This paper presents a comprehensive approach to analyze the dynamics of a generalized model of resonant inverters using nonsmooth dynamical system theory. The model simultaneously covers both parallel and series resonant inverters under state feedback control. The multi-parametric physical space is
reduced to a plane, which is divided in several regions with different dynamical behavior. The boundaries separating these regions are located by solving their corresponding equations and it is found that they all emerge from a singular point in the parameter plane. Suitability for applications of these regions is emphasized, thus providing useful criteria for parameter selection.
2020-01-28T19:38:52ZBenadero García-Morato, LuisTorres Peral, FranciscoPonce Núñez, EnriqueEl Aroudi, AbdelaliThis paper presents a comprehensive approach to analyze the dynamics of a generalized model of resonant inverters using nonsmooth dynamical system theory. The model simultaneously covers both parallel and series resonant inverters under state feedback control. The multi-parametric physical space is
reduced to a plane, which is divided in several regions with different dynamical behavior. The boundaries separating these regions are located by solving their corresponding equations and it is found that they all emerge from a singular point in the parameter plane. Suitability for applications of these regions is emphasized, thus providing useful criteria for parameter selection.Evidence for a dynamics crossover and its implication on the freezing temperature determination of relaxor ferroelectricsLevit Valenzuela, RafaelOchoa Guerrero, Diego A.Martínez García, Julio CesarGarcía García, José Eduardohttp://hdl.handle.net/2117/1719972020-10-01T00:28:17Z2019-11-08T15:35:17ZEvidence for a dynamics crossover and its implication on the freezing temperature determination of relaxor ferroelectrics
Levit Valenzuela, Rafael; Ochoa Guerrero, Diego A.; Martínez García, Julio Cesar; García García, José Eduardo
Relaxor ferroelectrics are characterized by a broadened and dispersive permittivity peak in their temperature-dependent dielectric spectra. Although several models have been proposed to explain the nature of these materials, understanding their relaxation dynamics still remains open and requires additional theoretical and experimental explanations. Particularly, a precise determination of the freezing temperature still remains controversial because the influence of dynamic ruptures at temperatures approaching the freezing states (dynamic crossovers) has never evaluated before. In this paper, a model-free approach for describing the super-Arrhenius behaviour in glassy systems is validated for relaxor ferroelectrics. As a result, a predicted dynamic change at a specific temperature (crossover temperature) is evidenced by a derivative-based representation of the relaxation time data. The Stickel function is suggested as a more straightforward but model-dependent method for obtaining the dynamic crossover temperature. Furthermore, the divergence (freezing) temperature is obtained on the basis of the Grüneisen-style activation energy temperature index without assuming any model equation for parameterizing the relaxation data. The influence of the dynamic change occurrences on the freezing temperature determination is also considered, showing that the dynamic crossover temperature determination is a key factor for a proper finding of the freezing temperature in relaxor ferroelectrics.
2019-11-08T15:35:17ZLevit Valenzuela, RafaelOchoa Guerrero, Diego A.Martínez García, Julio CesarGarcía García, José EduardoRelaxor ferroelectrics are characterized by a broadened and dispersive permittivity peak in their temperature-dependent dielectric spectra. Although several models have been proposed to explain the nature of these materials, understanding their relaxation dynamics still remains open and requires additional theoretical and experimental explanations. Particularly, a precise determination of the freezing temperature still remains controversial because the influence of dynamic ruptures at temperatures approaching the freezing states (dynamic crossovers) has never evaluated before. In this paper, a model-free approach for describing the super-Arrhenius behaviour in glassy systems is validated for relaxor ferroelectrics. As a result, a predicted dynamic change at a specific temperature (crossover temperature) is evidenced by a derivative-based representation of the relaxation time data. The Stickel function is suggested as a more straightforward but model-dependent method for obtaining the dynamic crossover temperature. Furthermore, the divergence (freezing) temperature is obtained on the basis of the Grüneisen-style activation energy temperature index without assuming any model equation for parameterizing the relaxation data. The influence of the dynamic change occurrences on the freezing temperature determination is also considered, showing that the dynamic crossover temperature determination is a key factor for a proper finding of the freezing temperature in relaxor ferroelectrics.Delay effects on the limit cycling behavior in resonant inverters with state feedbackBenadero García-Morato, LuisEl Aroudi, AbdelaliPonce, Enriquehttp://hdl.handle.net/2117/1708262020-07-23T21:42:03Z2019-10-24T17:42:30ZDelay effects on the limit cycling behavior in resonant inverters with state feedback
Benadero García-Morato, Luis; El Aroudi, Abdelali; Ponce, Enrique
Bifurcations of limit cycles in an H-bridge LC resonant inverter are reexamined taking into account a time delay in the switching transition. The analysis is accomplished by means of a model of the inverter that compresses, in only three parameters, all the elements associated to both series and parallel topologies of the inverter, to the parasitic effects, to the state feedback control, and to the switching time delay. Emphasis is made in the deviation of preexisting bifurcations without delay and the new ones arising when the time delay is taken into account. It is shown from the analysis and numerical simulations that the delay can degrade the quality of oscillations and even inhibit them, but it is also demonstrated that to some extent, this drawback can be compensated by an appropriate state feedback.
2019-10-24T17:42:30ZBenadero García-Morato, LuisEl Aroudi, AbdelaliPonce, EnriqueBifurcations of limit cycles in an H-bridge LC resonant inverter are reexamined taking into account a time delay in the switching transition. The analysis is accomplished by means of a model of the inverter that compresses, in only three parameters, all the elements associated to both series and parallel topologies of the inverter, to the parasitic effects, to the state feedback control, and to the switching time delay. Emphasis is made in the deviation of preexisting bifurcations without delay and the new ones arising when the time delay is taken into account. It is shown from the analysis and numerical simulations that the delay can degrade the quality of oscillations and even inhibit them, but it is also demonstrated that to some extent, this drawback can be compensated by an appropriate state feedback.The generalized Vogel-Fulcher-Tamman equation for describing the dynamics of relaxor ferroelectricsLevit Valenzuela, RafaelMartínez García, Julio CesarOchoa Guerrero, Diego A.García García, José Eduardohttp://hdl.handle.net/2117/1684852020-07-23T20:39:34Z2019-09-19T17:50:04ZThe generalized Vogel-Fulcher-Tamman equation for describing the dynamics of relaxor ferroelectrics
Levit Valenzuela, Rafael; Martínez García, Julio Cesar; Ochoa Guerrero, Diego A.; García García, José Eduardo
Relaxor ferroelectrics (RF) are outstanding materials owing to their extraordinary dielectric, electromechanical, and electro-optical properties. Although their massive applications, they remain to be one of the most puzzling solid-state materials because understanding their structural local order and relaxation dynamics is being a long-term challenge in materials science. The so-called Vogel-Fulcher-Tamman (VFT) relation has been extensively used to parameterize the relaxation dynamics in RF, although no microscopic description has been firmly established for such empirical relation. Here, we show that VFT equation is not always a proper approach for describing the dielectric relaxation in RF. Based on the Adam-Gibbs model and the Grüneisen temperature index, a more general equation to disentangle the relaxation kinetic is proposed. This approach allows to a new formulation for the configurational entropy leading to a local structural heterogeneity related order parameter for RF. A new pathway to disentangle relaxation phenomena in other relaxor ferroics could have opened.
2019-09-19T17:50:04ZLevit Valenzuela, RafaelMartínez García, Julio CesarOchoa Guerrero, Diego A.García García, José EduardoRelaxor ferroelectrics (RF) are outstanding materials owing to their extraordinary dielectric, electromechanical, and electro-optical properties. Although their massive applications, they remain to be one of the most puzzling solid-state materials because understanding their structural local order and relaxation dynamics is being a long-term challenge in materials science. The so-called Vogel-Fulcher-Tamman (VFT) relation has been extensively used to parameterize the relaxation dynamics in RF, although no microscopic description has been firmly established for such empirical relation. Here, we show that VFT equation is not always a proper approach for describing the dielectric relaxation in RF. Based on the Adam-Gibbs model and the Grüneisen temperature index, a more general equation to disentangle the relaxation kinetic is proposed. This approach allows to a new formulation for the configurational entropy leading to a local structural heterogeneity related order parameter for RF. A new pathway to disentangle relaxation phenomena in other relaxor ferroics could have opened.