title: Structural and electrical characterisation of some ABO₃ perovskites

authors: Phillips, Roslyn June

abstract: Powder X-ray diffraction and Raman spectroscopy have been used to characterise the electrolyte materials La₁₋ₓSrₓGaO₃₋δ (x = 0-0.2) and LaGa₁₋yMyO₃₋δ (y = 0-0.2, M = Cr, Mg). XRD of La₁₋ₓSrₓGaO₃₋δ (x = 0-0.2) showed the secondary phase of SrGa₃O₇ at >5 mol% Sr. The cell deformed with increasing Sr dopant concentration. In the XRD patterns of LaGa₁₋yCryO₃₋δ (y = 0-0.2) the cell also deformed with increasing Cr dopant concentration. The peak at ca. 32° showed a second peak at 32.37°, likely to be due to a phase change, since the peaks did not alter in relative intensity with increase in dopant concentration (above x = 0). LaGa₁₋yMgyO₃₋δ (y = 0-0.2) showed, from the powder X-ray diffraction pattern, the formation of the secondary phase of La₄Ga₂O₉ at >5 mol% Mg. Raman spectra of LaGaO₃ showed 18 features at room temperature, and 14 at -196 °C with the disappearance of the band at 92 cm⁻¹.  Raman spectra of the doped material, LaGa₁₋yMgyO₃₋δ at y = 0-0.2 showed the formation of a secondary phase of La₄Ga₂O₉ with bands at 243, 295 and 356 cm⁻¹ which become more predominant at 20 mol % Mg.

LaFeO₃ was prepared using a reverse-strike coprecipitation method. The Raman spectrum of LaFeO₃ were obtained at both low-temperature and room temperature, with 9 bands observed of a predicted 24 Raman active modes. Mode assignment was determined from comparison of the Raman profile and band position with perovskites with the same structure, namely, SmAlO₃ and LaGaO₃ and are as follows: 102 (B₁g ), ca.140 (B₂g), 150 (B₁g), 176 (Ag), 227 (B₃g), 261 (Ag), 289 (Ag), 413 (Ag), 429 (B₃g). LaFe₁₋ₓMgₓO₃ was prepared using a reverse-strike coprecipitation method. The XRD patterns obtained at room temperature showed single phase, but also included small amounts of impurity of La₂O₃ and La₂MgOₓ. Lattice calculations based on FeLaO₃ showed that Mg dopant concentration had a minor effect on the overall unit cell volume, with the minimum volume achieved being 241.68Å³ at 1450 °C, 15%Mg concentration. In summary, Mg-doped LaFeO₃ produced a single phase material in the range 0-20 mol% Mg as observed from X-ray diffraction. However, a small amount of impurities in each of the samples was observed, containing La₂O₃ and La₂MgOₓ. The presence of the impurities suggested that an extra calcination step be included in the processing of the material.

LaGdO₃ was fabricated using reverse strike co-precipitation method and sintered at temperature of 1350, 1400 and 1450 °C. X-ray diffraction showed the presence of a single monoclinic phase. Raman spectroscopy showed a spectrum similar for that reported for the B-type rare earth oxide Gd₂O₃ and the band positions of the low temperature Raman spectrum were assigned in comparison with this. A total of 18 bands were identified. Intense broad profile in the region 1000-2000 cm⁻¹ was observed for LaGdO₃, likely due to fluorescent/luminescent bands.

The acceptor-doped perovskite proton conductor SrCe₁₋ₓYₓO₃₋δ (x=0.025 to 0.20, δ = x/2) was prepared and characterised using X-ray diffraction and AC impedance spectroscopy, and the effect of the yttrium dopant concentration on structure and electrical properties has been investigated. X-ray diffraction studies showed a decrease in lattice volume with increasing yttrium content. Electrical conductivity studies were made as a function of oxygen partial pressure, and a partial pressure of water vapour of 0.001 and 0.01 atm. The total conductivity was separated into different components by fitting procedures and regions of ionic and p-type conduction were identified. At 800°C, and at the water vapour partial pressure of 0.01 atm, the ionic conductivity showed a maximum at a doping level of x = 0.10, reaching a value of 5 mS/cm. The conductivity component appearing at low oxygen partial pressure, which according to recent studies may be regarded as protonic rather than n-type, decreased with doping, while the p-type component at high oxygen partial pressure increased.

text: Structural and electrical characterisation of some ABO₃ perovskites Powder X-ray diffraction and Raman spectroscopy have been used to characterise the electrolyte materials La₁₋ₓSrₓGaO₃₋δ (x = 0-0.2) and LaGa₁₋yMyO₃₋δ (y = 0-0.2, M = Cr, Mg). XRD of La₁₋ₓSrₓGaO₃₋δ (x = 0-0.2) showed the secondary phase of SrGa₃O₇ at >5 mol% Sr. The cell deformed with increasing Sr dopant concentration. In the XRD patterns of LaGa₁₋yCryO₃₋δ (y = 0-0.2) the cell also deformed with increasing Cr dopant concentration. The peak at ca. 32° showed a second peak at 32.37°, likely to be due to a phase change, since the peaks did not alter in relative intensity with increase in dopant concentration (above x = 0). LaGa₁₋yMgyO₃₋δ (y = 0-0.2) showed, from the powder X-ray diffraction pattern, the formation of the secondary phase of La₄Ga₂O₉ at >5 mol% Mg. Raman spectra of LaGaO₃ showed 18 features at room temperature, and 14 at -196 °C with the disappearance of the band at 92 cm⁻¹.  Raman spectra of the doped material, LaGa₁₋yMgyO₃₋δ at y = 0-0.2 showed the formation of a secondary phase of La₄Ga₂O₉ with bands at 243, 295 and 356 cm⁻¹ which become more predominant at 20 mol % Mg.

LaFeO₃ was prepared using a reverse-strike coprecipitation method. The Raman spectrum of LaFeO₃ were obtained at both low-temperature and room temperature, with 9 bands observed of a predicted 24 Raman active modes. Mode assignment was determined from comparison of the Raman profile and band position with perovskites with the same structure, namely, SmAlO₃ and LaGaO₃ and are as follows: 102 (B₁g ), ca.140 (B₂g), 150 (B₁g), 176 (Ag), 227 (B₃g), 261 (Ag), 289 (Ag), 413 (Ag), 429 (B₃g). LaFe₁₋ₓMgₓO₃ was prepared using a reverse-strike coprecipitation method. The XRD patterns obtained at room temperature showed single phase, but also included small amounts of impurity of La₂O₃ and La₂MgOₓ. Lattice calculations based on FeLaO₃ showed that Mg dopant concentration had a minor effect on the overall unit cell volume, with the minimum volume achieved being 241.68Å³ at 1450 °C, 15%Mg concentration. In summary, Mg-doped LaFeO₃ produced a single phase material in the range 0-20 mol% Mg as observed from X-ray diffraction. However, a small amount of impurities in each of the samples was observed, containing La₂O₃ and La₂MgOₓ. The presence of the impurities suggested that an extra calcination step be included in the processing of the material.

LaGdO₃ was fabricated using reverse strike co-precipitation method and sintered at temperature of 1350, 1400 and 1450 °C. X-ray diffraction showed the presence of a single monoclinic phase. Raman spectroscopy showed a spectrum similar for that reported for the B-type rare earth oxide Gd₂O₃ and the band positions of the low temperature Raman spectrum were assigned in comparison with this. A total of 18 bands were identified. Intense broad profile in the region 1000-2000 cm⁻¹ was observed for LaGdO₃, likely due to fluorescent/luminescent bands.

The acceptor-doped perovskite proton conductor SrCe₁₋ₓYₓO₃₋δ (x=0.025 to 0.20, δ = x/2) was prepared and characterised using X-ray diffraction and AC impedance spectroscopy, and the effect of the yttrium dopant concentration on structure and electrical properties has been investigated. X-ray diffraction studies showed a decrease in lattice volume with increasing yttrium content. Electrical conductivity studies were made as a function of oxygen partial pressure, and a partial pressure of water vapour of 0.001 and 0.01 atm. The total conductivity was separated into different components by fitting procedures and regions of ionic and p-type conduction were identified. At 800°C, and at the water vapour partial pressure of 0.01 atm, the ionic conductivity showed a maximum at a doping level of x = 0.10, reaching a value of 5 mS/cm. The conductivity component appearing at low oxygen partial pressure, which according to recent studies may be regarded as protonic rather than n-type, decreased with doping, while the p-type component at high oxygen partial pressure increased.

year: 1999

title: Digital storytelling in an L2 context, and its impact on student communication, engagement, and motivation.

authors: Norton, Howard John

subjects: digital storytelling

abstract: The communicative second language (L2) classroom requires a dual focus. On the one hand, students must be motivated (willing) to communicate, and teachers need to create activities that promote and facilitate peer interaction. Allied to this, is a need for accuracy. However, some L2 learners communicate rarely, if at all, while others struggle to achieve accuracy due to the constraints of time and space, and a lack of teacher feedback in class. This study has adopted the visual (and conceptual) metaphor of Yin and Yang to symbolize the equilibrium needed within the ideal communicative L2 classroom. This study explores the behaviours and perspectives of a group of L2 learners creating culture-based digital stories on VoiceThread. It examines whether this digital storytelling project can have an impact on students’ communicative experience, both online and in the classroom, their motivation and engagement, and their levels of spoken output in class.

This interpretive study recognizes learner behaviours and perspectives as being unique to both the individual and the setting. A literature review presents an overview of digital storytelling, as well as research relevant to the pedagogical, affective, and technological aspects of this study. Data was collected through observation, interviews, and analysis of the digital stories. Findings indicate this digital storytelling project had a positive impact upon students’ communicative experience in different ways, which emphasizes the value of a subjectivist approach. The results also suggest high levels of motivation and communication.

This study suggests the constituent elements of this digital storytelling project can enhance the overall communicative experience, promote spoken communication in the classroom, and motivate students. This thesis concludes by offering a series of recommendations for educators, to facilitate meaningful interactivity, and place the student and their culture at the centre of the learning experience.

text: Digital storytelling in an L2 context, and its impact on student communication, engagement, and motivation. The communicative second language (L2) classroom requires a dual focus. On the one hand, students must be motivated (willing) to communicate, and teachers need to create activities that promote and facilitate peer interaction. Allied to this, is a need for accuracy. However, some L2 learners communicate rarely, if at all, while others struggle to achieve accuracy due to the constraints of time and space, and a lack of teacher feedback in class. This study has adopted the visual (and conceptual) metaphor of Yin and Yang to symbolize the equilibrium needed within the ideal communicative L2 classroom. This study explores the behaviours and perspectives of a group of L2 learners creating culture-based digital stories on VoiceThread. It examines whether this digital storytelling project can have an impact on students’ communicative experience, both online and in the classroom, their motivation and engagement, and their levels of spoken output in class.

This interpretive study recognizes learner behaviours and perspectives as being unique to both the individual and the setting. A literature review presents an overview of digital storytelling, as well as research relevant to the pedagogical, affective, and technological aspects of this study. Data was collected through observation, interviews, and analysis of the digital stories. Findings indicate this digital storytelling project had a positive impact upon students’ communicative experience in different ways, which emphasizes the value of a subjectivist approach. The results also suggest high levels of motivation and communication.

This study suggests the constituent elements of this digital storytelling project can enhance the overall communicative experience, promote spoken communication in the classroom, and motivate students. This thesis concludes by offering a series of recommendations for educators, to facilitate meaningful interactivity, and place the student and their culture at the centre of the learning experience.

year: 2014

title: Planning and governance under the LGA: Lessons from the RMA experience.

authors: Borrie, Nancy

subjects: New Zealand

abstract: The purpose of this report is to identify ways in which experiences gained from the
RMA as a devolved and co-operative planning mandate can enable local and central
government and other stakeholders to more effectively implement the LGA. The
report is based on findings from the FRST-funded research programme on Planning
under Co-operative Mandates (PUCM). We argue in this report that the experiences gained from the RMA can inform
effective implementation of the LGA in three important respects: Preparation and implementation of LTCCPs; The community consultation process for formulating community outcomes;
and Māori participation in planning and governance.

text: Planning and governance under the LGA: Lessons from the RMA experience. The purpose of this report is to identify ways in which experiences gained from the
RMA as a devolved and co-operative planning mandate can enable local and central
government and other stakeholders to more effectively implement the LGA. The
report is based on findings from the FRST-funded research programme on Planning
under Co-operative Mandates (PUCM). We argue in this report that the experiences gained from the RMA can inform
effective implementation of the LGA in three important respects: Preparation and implementation of LTCCPs; The community consultation process for formulating community outcomes;
and Māori participation in planning and governance.

year: 2004-06-01