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High-entropy ceramics have potential to improve the mechanical properties and high-temperature stability over traditional ceramics, and high entropy nitrides and carbonitrides (HENs and HECNs) are particularly attractive for high temperature and high hardness applications. The synthesis of 5 bulk HENs and 4 bulk HECNs forming single-phase materials is reported herein among 11 samples prepared. The hardness of HENs and HECNs increased by an average of 22% and 39%, respectively, over the rule-of-mixtures average of their monocarbide and mononitride precursors. Similarly, elastic modulus values increased by an average of 17% in nitrides and 31% in carbonitrides over their rule-of-mixtures values. The enhancement in mechanical properties is tied to an increase in the configurational entropy and a decrease in the valence electron concentration, providing parameters for tuning mechanical properties of high-entropy ceramics.

Ternary nitride semiconductors with wurtzite-derived crystal structures are an emerging class of materials for optoelectronic applications compatible with GaN and related III-V compounds. In particular, II-IV-V2 materials such as ZnSnN2 and ZnGeN2 have been very actively studied for applications in photovoltaics and light emitting devices. However, many other possible wurtzite-derived ternary nitrides have not been reported, and hence their optical and electrical properties remain unknown. Here, we report on Zn2SbN3-the first Sb-based nitride and a photoactive semiconductor. Surprisingly, Zn2SbN3 contains Sb in the highest (5+) oxidation state, and in the unusual tetrahedral coordination. This new Zn2SbN3 material has a solar-matched 1.6-1.7 eV band gap and shows near-band-edge room-temperature photoluminescence, demonstrating its promise as an optoelectronic semiconductor. Finally, Zn2SbN3 can be synthesized at low temperature under a wide range of processing conditions, despite being metastable according to theoretical calculations. All these results, as well as the band position measurements, indicate that Zn2SbN3 is a promising emerging semiconductor for applications as an absorber in photovoltaic-and photoelectrochemical solar cells.

Ternary nitride semiconductors with wurtzite-derived crystal structures are an emerging class of materials for optoelectronic applications compatible with GaN and related III-V compounds. In particular, II-IV-V2 materials such as ZnSnN2 and ZnGeN2 have been very actively studied for applications in photovoltaics and light emitting devices. However, many other possible wurtzite-derived ternary nitrides have not been reported, and hence their optical and electrical properties remain unknown. Here, we report on Zn2SbN3-the first Sb-based nitride and a photoactive semiconductor. Surprisingly, Zn2SbN3 contains Sb in the highest (5+) oxidation state, and in the unusual tetrahedral coordination. This new Zn2SbN3 material has a solar-matched 1.6-1.7 eV band gap and shows near-band-edge room-temperature photoluminescence, demonstrating its promise as an optoelectronic semiconductor. Finally, Zn2SbN3 can be synthesized at low temperature under a wide range of processing conditions, despite being metastable according to theoretical calculations. All these results, as well as the band position measurements, indicate that Zn2SbN3 is a promising emerging semiconductor for applications as an absorber in photovoltaic-and photoelectrochemical solar cells.

The design and tailoring of material color for both aesthetic and functionality is an ongoing topic of materials science and engineering research. In this work, a method is developed to tune and predict color and pseudogap energy of any compositional variation of B1-rocksalt structured Group 4 and 5 transition metal carbonitride. Optical properties of bulk multicomponent transition metal carbonitrides were characterized using reflectivity spectra. Optical pseudogap energies were extrapolated using the Tauc method, and color appearance was quantified in the Commission Internationale de l’Eclairage (CIE) Lightness*Chroma*hue (L*C*h) color space. Variations of color parameters chroma and hue were analyzed in terms of pseudogap energies and electronic band structures. Compositional variations were utilized to predictably tune aspects of the electronic structure, including the specificity of electronic transitions and the energy at which they occur, to tailor the material’s color appearance and facilitate the formation of new carbonitride colors.

This article explores distinctive features of a 5-year international education development project set in rural northern Peru (PROMEB, the "Proyecto de Mejoramiento de la Educacion Basica"). Grounded within a partnership between teacher educators from Peru, Mexico and Canada, and rural Peruvian teachers, students and their communities, we offer reflections on a teacher education initiative which sought to support action-orientated inquiries as a mechanism for school/community development. Set against a background of poverty, hunger, isolation and an "educational crisis", we outline our pedagogy and describe two projects. We then reflect on the influences of our engagements and on associated tensions and ambiguities in our methods. We hope that such discussions might offer insights for others involved in international school/community development projects of this type.

This article responds to Bruce Collet's article "From Refuge to Polis: Shifting the Rationale for Religiosity in Schools." In this rejoinder my intention is to shift the discussion from school-as-refuge to school-as-polis and to ask whether the integration interests of recent immigrants and refugees might not be better served by a more inclusive approach to religiosity in schools that is less about collective exception and more about social transformation.

This paper offers reflections on two transformative teacher education projects. The first a global communities module is set in a university in Vancouver and utilizes the lens of social ecology to examine the roles of teachers in bringing an awareness of local/global issues to their students' learning experiences. The second, a Canadian International Development Agency (CIDA) teacher education project located in rural Peru, involves the collaboration of universities in Canada, Mexico and Peru. The projects are united in their use of "critical place-based" transformative teacher education agendas and democratic participatory methods. We use our experiences in these projects combined with relevant literature to explore three questions: (1) What inspirations might be drawn from our critical place-based participatory approaches? (2) What might these approaches offer in response to the United Nation's Decade of Education for Sustainable Development [UNDESD]? (3) Does the UN Decade provides a conceptual framework to instigate and support social and ecological transformation?

This paper begins with the observation that, for a variety of social, political, and economic reasons, many universities are beginning to rethink the nature of their relations with local communities and asks about the place of Faculties of Education in such processes of reconsideration. It describes recent initiatives at York University as examples of what might be possible.

Defines education for sustainability and contrasts its ethical positions with current approaches to career development. Argues that sustainability is a useful framework for locating vocational education within the context of efforts to address equity, social justice, and economic and environmental issues. (SK)

This article uses discourse theory in arguing that learning disabilities, by explaining several contradictions and anomalies of schooling, function to sustain dominant assumptions of schooling and society and to maintain inequitable distribution of social goods. Educators are urged to actively confront the inequities of schooling and society. (Author/DB)

Calls for resolution of the ambiguities and contradictions of the language and the practices of whole language. Attempts to elucidate conflicting conceptions and practices among whole-language advocates and thereby make whole language even stronger. (MG)

Time-resolved photoluminescence (TRPL) measurements are used to evaluate and distinguish the roles of S diffusion, initial absorber quality and Ad[Cl.sub.2] treatment on recombination in polycrystalline CdTe. Low-temperature PL, cathodoluminescence and scanning electron images have shown how defect chemistry, grain-boundary passivation, and morphology are affected by S diffusion and the Cd[Cl.sub.2] treatments.

World-record power conversion efficiencies for Cu(In,Ga)Se2 (CIGS) solar cells have been achieved via a post-deposition treatment with alkaline metals, which increases the open-circuit voltage and fill factor. We explore the role of the potassium fluoride (KF) post-deposition treatment in CIGS by employing energy- and time-resolved photoluminescence spectroscopy and electrical characterization combined with numerical modeling. The bulk carrier lifetime is found to increase with post-deposition treatment from 255 ns to 388 ns, which is the longest charge carrier lifetime reported for CIGS, and within ∼40% of the radiative limit. We find evidence that the post-deposition treatment causes a decrease in the electronic potential fluctuations. These potential fluctuations have previously been shown to reduce the open-circuit voltage and the device efficiency in CIGS. Additionally, numerical simulations based on the measured carrier lifetimes and mobilities show a diffusion length of ∼10 lm, which is ∼4 times larger than the film thickness. Thus, carrier collection in the bulk is not a limiting factor for device efficiency. By considering differences in doping, bandgap, and potential fluctuations, we present a possible explanation for the voltage difference between KF-treated and untreated samples. [ABSTRACT FROM AUTHOR]

Solar cells based on kesterite absorbers consistently show lower voltages than those based on chalcopyrites with the same bandgap. We use three different experimental methods and associated data analysis to determine minority-carrier lifetime in a 9.4%-efficient Cu2ZnSnSe4 device. The methods are cross-sectional electron-beam induced current, quantum efficiency, and time-resolved photoluminescence. These methods independently indicate minority-carrier lifetimes of a few nanoseconds. A comparison of current-voltage measurements and device modeling suggests that these short minority-carrier lifetimes cause a significant limitation on the voltage produced by the device. The comparison also implies that low minority-carrier lifetime alone does not account for all voltage loss in these devices. [ABSTRACT FROM AUTHOR]

Central to a pedagogy of work education is a practice that must acknowledge experience as legitimate curricular content while simultaneously challenging both its substance and its form. Several variations of how work experience is constituted by students are discussed, and the pedagogical implications of each is explored. (Author/BJV)

Assesses the potential of occupational analysis to redefine the aims of work education to afford students increased participation in the social and economic changes characterizing contemporary work. Faults the prevalence of "social efficiency" over "social growth" in educational objectives, advocating instructional emphasis on interrelations between technological, organizational, and political factors. (DMM)

Time-resolved photoluminescence measurements on glass/SnO2/CdTe and glass/SnO2/CdTe/CdS structures indicate that the CdCl2 process, without any S present, significantly reduces recombination. However, S diffusion is required for lifetimes comparable to those observed in high-efficiency solar cells. Low-temperature photoluminescence, cathodoluminescence, and scanning electron images indicate how defect chemistry, grain-boundary passivation, and morphology are affected by S diffusion and the CdCl2 treatment. [ABSTRACT FROM AUTHOR]

The changes in dominant recombination mechanisms of Cu(In,Ga)Se[sub 2] thin films grown from (In,Ga)[sub 2]Se[sub 3] precursors are investigated using energy- and time-resolved photoluminescence. The results are analyzed with a rate-equation analysis and correlated with n/p diode measurements on processed devices. The experimental results quantify a change in the dominant radiative process and an improvement in the underlying material quality. These observations support a growth model incorporating changes in the dominant defect states and recombination mechanisms during this final stage of the growth process. Additionally, evidence is presented that supports the passivation of near-surface recombination sites by CdS. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]