A series of compounds La 2 Mo 2−x W x O 9 (x = 0-2) were synthesized using a freeze-dried precurs... more A series of compounds La 2 Mo 2−x W x O 9 (x = 0-2) were synthesized using a freeze-dried precursor method at relatively low temperatures (673-823 K). These materials were characterised by thermogravimetric and differential thermal analysis (TG/DTA), differential scanning calorimetric (DSC), X-ray diffraction (XRD), and transmission electron microscopy (TEM) and dilatometric measurements. Oxygen stoichiometry was evaluated by coulometric titration and thermogravimetric analysis at 873-1273 K. The ionic and electronic conductivities of these materials were analysed by impedance spectroscopy and a Hebb-Wagner ion-blocking method under moderately reducing conditions. The presence of W 6+ leads to an increase of the stability range (about 10 −16 Pa for La 2 Mo 0.5 W 1.5 O 9 at 1073 K) and prevents oxygen loss and amorphisation. Within the stability range, the electronic conductivity increases gradually as the temperature increases and as the oxygen partial pressure reduces. This indicates that the electronic transport is mainly n-type as a result of the oxygen-content decreasing in the molybdate lattice. Further reduction of the oxygen partial pressure gave rise to the decomposition of La 2 Mo 2−x W x O 9 , leading to the formation of new phases with molybdenum in lower oxidation states, which further enhances the electronic conductivity. The results of the coulometric titration and the thermogravimetric studies under a dry 5% H 2 /Ar flow suggest that tungsten doped lanthanum molybdate materials can be used as electrolyte only at low temperature and under moderate reducing conditions.
The combined use of 3D Laser Range Finders (LRF) and cameras is increasingly common in the naviga... more The combined use of 3D Laser Range Finders (LRF) and cameras is increasingly common in the navigation application for autonomous mobile robots. The integration of laser range information and images requires the estimation of the Euclidean 3-dimensional transformation between the coordinate systems of the LRF and the cameras. This paper describes a new and efficient method to perform the extrinsic calibration between a 3D LRF and a stereo camera with the aid of inertial data. The main novelty of the proposed approach compared to other state of the art calibration procedures is the use of an Inertial Measurement Unit (IMU), which decreases the number of points needed to a robust calibration. Furthermore, a freely moving bright spot is the only calibration object. A set of virtual 3D points is made by waving the bright spot through the working volume in three different planes. Its projections onto the images are found with sub-pixel precision and verified by a robust RANSAC analysis. These same points are extracted according to the laser scan data and are corresponded to the virtual 3D points in the stereo pair. Experimental results presented in this paper demonstrate the accuracy of our approach. Furthermore, the applicability of the proposed technique is high, only requiring of an inertial sensor coupled to the sensor platform. This approach has been also extended for a camera network.
Commercial ceria -gadolinia powders were used to obtain bulk CGO samples, by sintering at 900 to ... more Commercial ceria -gadolinia powders were used to obtain bulk CGO samples, by sintering at 900 to 1500 -C with Co nitrate additions, or at temperatures in the range 1500 -1600 -C, without Co. These samples were characterized by impedance spectroscopy in air, at temperatures in the range 150 -600 -C, to distinguish the bulk and grain boundary behaviour. Addition of Co nitrate allows densification at lower temperatures and plays significant effects on both microstructural contributions of impedance spectra, enhancing the bulk and grain boundary conductivities and lowering their activation energy. Typical values of activation energy of bulk conductivity vary from 0.77 to 0.94 eV, and the activation energy of grain boundary conductivity were in the range 0.96 -1.05 eV. The effects of sintering additive are spoilt on raising the sintering temperature, due to depletion of Co content in grain boundaries of samples fired at high temperatures. These observations indicate that grain boundary behaviour may be determined by segregation of Co and/or Gd and the corresponding space charge layers, at least for materials prepared from high purity precursor powders. The p-type electronic conductivity is also enhanced for samples fired at relatively low temperatures with addition of Co, thus indicating that significant changes in defect chemistry occur. D
A study of optical properties and upconversion processes among Er ions in oxyfluoride glass and g... more A study of optical properties and upconversion processes among Er ions in oxyfluoride glass and glass ceramic matrix has been carried out. From optical absorption spectra, the oscillator strengths have been obtained for several transitions and they have been used to calculate the Judd-Ofelt parameters. Experimental lifetime values are compared with those obtained with the Judd-Ofelt theory. Different 31 upconversion emissions at 545, 660 and 800 nm have been obtained in Er doped glass and glass ceramics by exciting at 975 nm. A systematic investigation of the green upconversion is reported with the purpose of determining the involved upconversion mechanisms.
In this paper, an approach for fitting a circle to 2-D data which represent only a small part of ... more In this paper, an approach for fitting a circle to 2-D data which represent only a small part of the curve is described. This approach deals with the particular case where data is specified in terms of its Cartesian coordinates and the errors in both coordinates are not independent. Besides, an associated uncertainty ellipse which describes the measurement error and
Aims Stevioside is a natural plant glycoside isolated from the plant Stevia rebaudiana which has ... more Aims Stevioside is a natural plant glycoside isolated from the plant Stevia rebaudiana which has been commercialized as a sweetener in Japan for more than 20 years. Previous animal studies have shown that stevioside has an antihypertensive effect. This study was to designed to evaluate the effect of stevioside in human hypertension. Methods A multicentre, randomized, double-blind, placebo-controlled study was undertaken. This study group consisted of 106 Chinese hypertensive subjects with diastolic blood pressure between 95 and 110 mmHg and ages ranging from 28 to 75 years with 60 subjects (men 34, women 26; mean t s.d., 54.1t3.8 years) allocated to active treatment and 46 (men 19, women 27; mean t s.d., 53.7t4.1 years) to placebo treatment. Each subject was given capsules containing stevioside (250 mg) or placebo thrice daily and followed-up at monthly intervals for 1 year. Results After 3 months, the systolic and diastolic blood pressure of the stevioside group decreased signi®cantly (systolic: 166.0t9.4±152.6t6.8 mmHg; diastolic: 104.7t5.2±90.3t3.6 mmHg, P<0.05), and the effect persisted during the whole year. Blood biochemistry parameters including lipid and glucose showed no signi®cant changes. No signi®cant adverse effect was observed and quality of life assessment showed no deterioration. Conclusions This study shows that oral stevioside is a well tolerated and effective modality that may be considered as an alternative or supplementary therapy for patients with hypertension.
A facile and versatile method using polymethyl methacrylate (PMMA) microspheres as pore formers h... more A facile and versatile method using polymethyl methacrylate (PMMA) microspheres as pore formers has been developed to prepare thin layer oxide materials with controlled macroporous microstructure. Several mixed oxides with fluorite and perovskite-type structures, i.e. doped zirconia, ceria, ferrites, manganites, and NiO-YSZ composites have been prepared and characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption and mercury porosimetry. The synthesised materials are nanocrystalline and present a homogeneous pore distribution and relatively high specific surface area, which makes them interesting for SOFC and catalysis applications in the intermediate temperature range. r
Hepatitis C virus (HCV) shows substantial nucleotide sequence diversity distributed throughout th... more Hepatitis C virus (HCV) shows substantial nucleotide sequence diversity distributed throughout the viral genome, with many variants showing only 68-79% overall sequence homology. This has led to problems in diagnosis of HCV using commercial immunoassays. Based on clustering of homologous sequences, various genotypes and subtypes of HCV have been described from different geographical regions. In the present study, 11 isolates from India were genotyped using sequence comparison for part of the non-structural (NS5) and structural (core) regions. Parts of the genome covering 451 bp (nt 9-459) of the core gene and a 249 bp fragment (nt 7959-8207) of the NS5 gene were reverse transcribed and amplified using nested polymerase chain reaction (RT-PCR). The amplified fragments were cloned and sequenced. The classification into genotypes was done on the basis of phylogenetic analysis. Four isolates showed sequence homology to type 1b. Two of the isolates were classified as type 3a. One isolate was classified as type 3b and the remaining four isolates were found to be variants of type 3 but did not belong to any designated subtype. On the basis of phylogenetic analysis two of the unclassified isolates were put into a new subtype of 3 named as 3g. In one of these variants, parts of a 5&#39;-noncoding (5&#39; NCR; 204 bp), envelope-E1 (435 bp), and NS3 (502 bp) regions were also amplified, cloned, and sequenced. This study demonstrates the type 3 variants including a new subtype (3g) to be the major cause of HCV infection in India.
Additions of 2 mol% CoO1.333 into gadolinia-doped ceria (CGO) solid electrolyte considerably impr... more Additions of 2 mol% CoO1.333 into gadolinia-doped ceria (CGO) solid electrolyte considerably improve sinterability and make it possible to obtain Ce0.8Gd0.2O2−δ ceramics with 95–99% density at 1173–1373 K. The effect of cobalt oxide on the total electrical conductivity in air is negligible if the sintering is performed at 1173 K, although p-type electronic conduction measured at 900–1200 K increases with
The apatite La 10-x 0 x (Ge 5.5 Al 0.5 O 24 )O 2.75-1.5x (10x ) 9. 80, 9.75, 9.67, 9.60, 9.50, an... more The apatite La 10-x 0 x (Ge 5.5 Al 0.5 O 24 )O 2.75-1.5x (10x ) 9. 80, 9.75, 9.67, 9.60, 9.50, and 9.40) series has been prepared and the single phase existence range has been established, 9.75 g 10x g 9.45. The hexagonal crystal structures of La 9.5 0 0.5 (Ge 5.5 Al 0.5 O 24 )O 2 have been determined at room temperature, 500°C, and 900°C from neutron powder diffraction data using the Rietveld method. The room-temperature unit cell parameters were a ) 9.9206(4) Å, c ) 7.2893(3) Å, V ) 621.29(6) Å 3 , and Z ) 1, and this refinement converged to R WP ) 3.03 and R F ) 1.30%. The most important structural result is the presence of interstitial oxygen ion associated with vacancies at the apatite oxide anions channels. Oxide ion conductivities have been measured by impedance spectroscopy. La 9.5 0 0.5 (Ge 5.5 Al 0.5 O 24 )O 2 shows very high oxide conductivity, 0.16(1) S‚cm -1 at 800°C, with negligible electronic contribution. The ionic transport number, obtained by combination of impedance and ion-blocking data, is higher than 0.99 in the studied oxygen partial pressure range, 0.21 to 10 -20
... Keywords: Natural landmark extraction; Mobile robot navigation; Adaptive curvature estimation... more ... Keywords: Natural landmark extraction; Mobile robot navigation; Adaptive curvature estimation; Covariance matrix. ... corners or walls) which can be described by items as line segments, corners or curve ... Applying vision to feature extraction leads to increase CPU usage due to the ...
Thermogravimetric analysis of yttrium–barium cobaltite phase, recently reported as YBaCo4O7, show... more Thermogravimetric analysis of yttrium–barium cobaltite phase, recently reported as YBaCo4O7, showed a higher oxygen content at temperatures below 1000K. This phase, equilibrated with atmospheric oxygen at room temperature, contains approximately 8.5 oxygen atoms per formula unit, suggesting that the dominant oxidation state of cobalt is +3. The high effective paramagnetic moment, μeff=5.55μB per Co ion, supports such conclusion and indicates
La2Mo2O9 ceramics have been prepared from freeze-dried precursors and their properties compared t... more La2Mo2O9 ceramics have been prepared from freeze-dried precursors and their properties compared to those of lantanum molybdate obtained by conventional solid state (SS) reaction. All materials have been characterized by X-ray diffraction, scanning electron microscopy and thermal analysis (TGA/DTA/DSC and dilatometry) to characterize the phase formation and phase transition. When the freeze-dried method was applied, the synthesis temperature required to
The effect of the structural phase transition on the electrical and electrochemical properties of... more The effect of the structural phase transition on the electrical and electrochemical properties of GdBaCo2O5+x has been analysed in order to evaluate its suitability as an electrode material for high-temperature applications, in particular as a cathode for Solid Oxide Fuel Cells (SOFCs). X-ray diffraction evolution with the temperature and differential scanning calorimetry were used to determine structural features of the
Increasing temperature from 973 to 1173 K leads to a substantial increase of the electronic contr... more Increasing temperature from 973 to 1173 K leads to a substantial increase of the electronic contribution to the total conductivity of undoped lanthanum molybdate and La 2 Mo 2 O 9 -based solid electrolytes, including La 2 Mo 1.7 W 0.3 O 9 , La 2 Mo 1.95 V 0.05 O 9 and La 1.7 Bi 0.3 Mo 2 O 9 , where the stabilization of -La 2 Mo 2 O 9 down to room temperature was confirmed by high-resolution X-ray diffraction (XRD) and differential scanning calorimetry (DSC) data. In air, the ion transference numbers determined by the modified Faradaic efficiency (FE) technique, decrease from 0.991-0.997 at 973-1023 K down to 0.977-0.984 at 1173 K. Reducing oxygen partial pressure also increases electronic conduction evaluated by the emf and oxygen permeability (OP) measurements, which indicates that the electronic transport is n-type, resulting from decreasing oxygen content in the molybdate lattice. The level of n-type electronic conductivity in air is quite similar for all La 2 Mo 2 O 9 -based ceramics. The results show that these materials can be used as solid electrolytes only under oxidizing conditions and only at temperatures below 1073 K. Their practical applications may also be complicated due to relatively high thermal expansion coefficients (CTEs), (14.1-14.8) × 10 −6 K −1 at 300-700 K and (16.4-22.5) × 10 −6 K −1 at 850-1070 K, which are close to those of stabilized ␦-Bi 2 O 3 and ␥-Bi 2 VO 5.5 electrolytes.
A modified freeze-dried method has been used to obtain polycrystalline powders of the ionic condu... more A modified freeze-dried method has been used to obtain polycrystalline powders of the ionic conductor La2Mo2O9. Such ceramic powders were characterized by TG/DTA, XRD, SEM and TEM, and their sinterability was analysed by dilatometry and isothermal sintering ...
A series of compounds La 2 Mo 2−x W x O 9 (x = 0-2) were synthesized using a freeze-dried precurs... more A series of compounds La 2 Mo 2−x W x O 9 (x = 0-2) were synthesized using a freeze-dried precursor method at relatively low temperatures (673-823 K). These materials were characterised by thermogravimetric and differential thermal analysis (TG/DTA), differential scanning calorimetric (DSC), X-ray diffraction (XRD), and transmission electron microscopy (TEM) and dilatometric measurements. Oxygen stoichiometry was evaluated by coulometric titration and thermogravimetric analysis at 873-1273 K. The ionic and electronic conductivities of these materials were analysed by impedance spectroscopy and a Hebb-Wagner ion-blocking method under moderately reducing conditions. The presence of W 6+ leads to an increase of the stability range (about 10 −16 Pa for La 2 Mo 0.5 W 1.5 O 9 at 1073 K) and prevents oxygen loss and amorphisation. Within the stability range, the electronic conductivity increases gradually as the temperature increases and as the oxygen partial pressure reduces. This indicates that the electronic transport is mainly n-type as a result of the oxygen-content decreasing in the molybdate lattice. Further reduction of the oxygen partial pressure gave rise to the decomposition of La 2 Mo 2−x W x O 9 , leading to the formation of new phases with molybdenum in lower oxidation states, which further enhances the electronic conductivity. The results of the coulometric titration and the thermogravimetric studies under a dry 5% H 2 /Ar flow suggest that tungsten doped lanthanum molybdate materials can be used as electrolyte only at low temperature and under moderate reducing conditions.
The combined use of 3D Laser Range Finders (LRF) and cameras is increasingly common in the naviga... more The combined use of 3D Laser Range Finders (LRF) and cameras is increasingly common in the navigation application for autonomous mobile robots. The integration of laser range information and images requires the estimation of the Euclidean 3-dimensional transformation between the coordinate systems of the LRF and the cameras. This paper describes a new and efficient method to perform the extrinsic calibration between a 3D LRF and a stereo camera with the aid of inertial data. The main novelty of the proposed approach compared to other state of the art calibration procedures is the use of an Inertial Measurement Unit (IMU), which decreases the number of points needed to a robust calibration. Furthermore, a freely moving bright spot is the only calibration object. A set of virtual 3D points is made by waving the bright spot through the working volume in three different planes. Its projections onto the images are found with sub-pixel precision and verified by a robust RANSAC analysis. These same points are extracted according to the laser scan data and are corresponded to the virtual 3D points in the stereo pair. Experimental results presented in this paper demonstrate the accuracy of our approach. Furthermore, the applicability of the proposed technique is high, only requiring of an inertial sensor coupled to the sensor platform. This approach has been also extended for a camera network.
Commercial ceria -gadolinia powders were used to obtain bulk CGO samples, by sintering at 900 to ... more Commercial ceria -gadolinia powders were used to obtain bulk CGO samples, by sintering at 900 to 1500 -C with Co nitrate additions, or at temperatures in the range 1500 -1600 -C, without Co. These samples were characterized by impedance spectroscopy in air, at temperatures in the range 150 -600 -C, to distinguish the bulk and grain boundary behaviour. Addition of Co nitrate allows densification at lower temperatures and plays significant effects on both microstructural contributions of impedance spectra, enhancing the bulk and grain boundary conductivities and lowering their activation energy. Typical values of activation energy of bulk conductivity vary from 0.77 to 0.94 eV, and the activation energy of grain boundary conductivity were in the range 0.96 -1.05 eV. The effects of sintering additive are spoilt on raising the sintering temperature, due to depletion of Co content in grain boundaries of samples fired at high temperatures. These observations indicate that grain boundary behaviour may be determined by segregation of Co and/or Gd and the corresponding space charge layers, at least for materials prepared from high purity precursor powders. The p-type electronic conductivity is also enhanced for samples fired at relatively low temperatures with addition of Co, thus indicating that significant changes in defect chemistry occur. D
A study of optical properties and upconversion processes among Er ions in oxyfluoride glass and g... more A study of optical properties and upconversion processes among Er ions in oxyfluoride glass and glass ceramic matrix has been carried out. From optical absorption spectra, the oscillator strengths have been obtained for several transitions and they have been used to calculate the Judd-Ofelt parameters. Experimental lifetime values are compared with those obtained with the Judd-Ofelt theory. Different 31 upconversion emissions at 545, 660 and 800 nm have been obtained in Er doped glass and glass ceramics by exciting at 975 nm. A systematic investigation of the green upconversion is reported with the purpose of determining the involved upconversion mechanisms.
In this paper, an approach for fitting a circle to 2-D data which represent only a small part of ... more In this paper, an approach for fitting a circle to 2-D data which represent only a small part of the curve is described. This approach deals with the particular case where data is specified in terms of its Cartesian coordinates and the errors in both coordinates are not independent. Besides, an associated uncertainty ellipse which describes the measurement error and
Aims Stevioside is a natural plant glycoside isolated from the plant Stevia rebaudiana which has ... more Aims Stevioside is a natural plant glycoside isolated from the plant Stevia rebaudiana which has been commercialized as a sweetener in Japan for more than 20 years. Previous animal studies have shown that stevioside has an antihypertensive effect. This study was to designed to evaluate the effect of stevioside in human hypertension. Methods A multicentre, randomized, double-blind, placebo-controlled study was undertaken. This study group consisted of 106 Chinese hypertensive subjects with diastolic blood pressure between 95 and 110 mmHg and ages ranging from 28 to 75 years with 60 subjects (men 34, women 26; mean t s.d., 54.1t3.8 years) allocated to active treatment and 46 (men 19, women 27; mean t s.d., 53.7t4.1 years) to placebo treatment. Each subject was given capsules containing stevioside (250 mg) or placebo thrice daily and followed-up at monthly intervals for 1 year. Results After 3 months, the systolic and diastolic blood pressure of the stevioside group decreased signi®cantly (systolic: 166.0t9.4±152.6t6.8 mmHg; diastolic: 104.7t5.2±90.3t3.6 mmHg, P<0.05), and the effect persisted during the whole year. Blood biochemistry parameters including lipid and glucose showed no signi®cant changes. No signi®cant adverse effect was observed and quality of life assessment showed no deterioration. Conclusions This study shows that oral stevioside is a well tolerated and effective modality that may be considered as an alternative or supplementary therapy for patients with hypertension.
A facile and versatile method using polymethyl methacrylate (PMMA) microspheres as pore formers h... more A facile and versatile method using polymethyl methacrylate (PMMA) microspheres as pore formers has been developed to prepare thin layer oxide materials with controlled macroporous microstructure. Several mixed oxides with fluorite and perovskite-type structures, i.e. doped zirconia, ceria, ferrites, manganites, and NiO-YSZ composites have been prepared and characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption and mercury porosimetry. The synthesised materials are nanocrystalline and present a homogeneous pore distribution and relatively high specific surface area, which makes them interesting for SOFC and catalysis applications in the intermediate temperature range. r
Hepatitis C virus (HCV) shows substantial nucleotide sequence diversity distributed throughout th... more Hepatitis C virus (HCV) shows substantial nucleotide sequence diversity distributed throughout the viral genome, with many variants showing only 68-79% overall sequence homology. This has led to problems in diagnosis of HCV using commercial immunoassays. Based on clustering of homologous sequences, various genotypes and subtypes of HCV have been described from different geographical regions. In the present study, 11 isolates from India were genotyped using sequence comparison for part of the non-structural (NS5) and structural (core) regions. Parts of the genome covering 451 bp (nt 9-459) of the core gene and a 249 bp fragment (nt 7959-8207) of the NS5 gene were reverse transcribed and amplified using nested polymerase chain reaction (RT-PCR). The amplified fragments were cloned and sequenced. The classification into genotypes was done on the basis of phylogenetic analysis. Four isolates showed sequence homology to type 1b. Two of the isolates were classified as type 3a. One isolate was classified as type 3b and the remaining four isolates were found to be variants of type 3 but did not belong to any designated subtype. On the basis of phylogenetic analysis two of the unclassified isolates were put into a new subtype of 3 named as 3g. In one of these variants, parts of a 5&#39;-noncoding (5&#39; NCR; 204 bp), envelope-E1 (435 bp), and NS3 (502 bp) regions were also amplified, cloned, and sequenced. This study demonstrates the type 3 variants including a new subtype (3g) to be the major cause of HCV infection in India.
Additions of 2 mol% CoO1.333 into gadolinia-doped ceria (CGO) solid electrolyte considerably impr... more Additions of 2 mol% CoO1.333 into gadolinia-doped ceria (CGO) solid electrolyte considerably improve sinterability and make it possible to obtain Ce0.8Gd0.2O2−δ ceramics with 95–99% density at 1173–1373 K. The effect of cobalt oxide on the total electrical conductivity in air is negligible if the sintering is performed at 1173 K, although p-type electronic conduction measured at 900–1200 K increases with
The apatite La 10-x 0 x (Ge 5.5 Al 0.5 O 24 )O 2.75-1.5x (10x ) 9. 80, 9.75, 9.67, 9.60, 9.50, an... more The apatite La 10-x 0 x (Ge 5.5 Al 0.5 O 24 )O 2.75-1.5x (10x ) 9. 80, 9.75, 9.67, 9.60, 9.50, and 9.40) series has been prepared and the single phase existence range has been established, 9.75 g 10x g 9.45. The hexagonal crystal structures of La 9.5 0 0.5 (Ge 5.5 Al 0.5 O 24 )O 2 have been determined at room temperature, 500°C, and 900°C from neutron powder diffraction data using the Rietveld method. The room-temperature unit cell parameters were a ) 9.9206(4) Å, c ) 7.2893(3) Å, V ) 621.29(6) Å 3 , and Z ) 1, and this refinement converged to R WP ) 3.03 and R F ) 1.30%. The most important structural result is the presence of interstitial oxygen ion associated with vacancies at the apatite oxide anions channels. Oxide ion conductivities have been measured by impedance spectroscopy. La 9.5 0 0.5 (Ge 5.5 Al 0.5 O 24 )O 2 shows very high oxide conductivity, 0.16(1) S‚cm -1 at 800°C, with negligible electronic contribution. The ionic transport number, obtained by combination of impedance and ion-blocking data, is higher than 0.99 in the studied oxygen partial pressure range, 0.21 to 10 -20
... Keywords: Natural landmark extraction; Mobile robot navigation; Adaptive curvature estimation... more ... Keywords: Natural landmark extraction; Mobile robot navigation; Adaptive curvature estimation; Covariance matrix. ... corners or walls) which can be described by items as line segments, corners or curve ... Applying vision to feature extraction leads to increase CPU usage due to the ...
Thermogravimetric analysis of yttrium–barium cobaltite phase, recently reported as YBaCo4O7, show... more Thermogravimetric analysis of yttrium–barium cobaltite phase, recently reported as YBaCo4O7, showed a higher oxygen content at temperatures below 1000K. This phase, equilibrated with atmospheric oxygen at room temperature, contains approximately 8.5 oxygen atoms per formula unit, suggesting that the dominant oxidation state of cobalt is +3. The high effective paramagnetic moment, μeff=5.55μB per Co ion, supports such conclusion and indicates
La2Mo2O9 ceramics have been prepared from freeze-dried precursors and their properties compared t... more La2Mo2O9 ceramics have been prepared from freeze-dried precursors and their properties compared to those of lantanum molybdate obtained by conventional solid state (SS) reaction. All materials have been characterized by X-ray diffraction, scanning electron microscopy and thermal analysis (TGA/DTA/DSC and dilatometry) to characterize the phase formation and phase transition. When the freeze-dried method was applied, the synthesis temperature required to
The effect of the structural phase transition on the electrical and electrochemical properties of... more The effect of the structural phase transition on the electrical and electrochemical properties of GdBaCo2O5+x has been analysed in order to evaluate its suitability as an electrode material for high-temperature applications, in particular as a cathode for Solid Oxide Fuel Cells (SOFCs). X-ray diffraction evolution with the temperature and differential scanning calorimetry were used to determine structural features of the
Increasing temperature from 973 to 1173 K leads to a substantial increase of the electronic contr... more Increasing temperature from 973 to 1173 K leads to a substantial increase of the electronic contribution to the total conductivity of undoped lanthanum molybdate and La 2 Mo 2 O 9 -based solid electrolytes, including La 2 Mo 1.7 W 0.3 O 9 , La 2 Mo 1.95 V 0.05 O 9 and La 1.7 Bi 0.3 Mo 2 O 9 , where the stabilization of -La 2 Mo 2 O 9 down to room temperature was confirmed by high-resolution X-ray diffraction (XRD) and differential scanning calorimetry (DSC) data. In air, the ion transference numbers determined by the modified Faradaic efficiency (FE) technique, decrease from 0.991-0.997 at 973-1023 K down to 0.977-0.984 at 1173 K. Reducing oxygen partial pressure also increases electronic conduction evaluated by the emf and oxygen permeability (OP) measurements, which indicates that the electronic transport is n-type, resulting from decreasing oxygen content in the molybdate lattice. The level of n-type electronic conductivity in air is quite similar for all La 2 Mo 2 O 9 -based ceramics. The results show that these materials can be used as solid electrolytes only under oxidizing conditions and only at temperatures below 1073 K. Their practical applications may also be complicated due to relatively high thermal expansion coefficients (CTEs), (14.1-14.8) × 10 −6 K −1 at 300-700 K and (16.4-22.5) × 10 −6 K −1 at 850-1070 K, which are close to those of stabilized ␦-Bi 2 O 3 and ␥-Bi 2 VO 5.5 electrolytes.
A modified freeze-dried method has been used to obtain polycrystalline powders of the ionic condu... more A modified freeze-dried method has been used to obtain polycrystalline powders of the ionic conductor La2Mo2O9. Such ceramic powders were characterized by TG/DTA, XRD, SEM and TEM, and their sinterability was analysed by dilatometry and isothermal sintering ...
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