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A structural crossover from non-ergodic to ergodic phase in niobium doped (Na0.41K0.09Bi0.5)TiO3, i.e., (Na0.41K0.09Bi0.50)1−x/2(Ti1−xNbx)O3 was investigated using high resolution x-ray diffraction and Raman spectroscopy. The diffraction studies reveal the co-existence of cubic (Pm3m), rhombohedral (R3c), and tetragonal (P4bm) phases for lower concentrations of niobium, i.e., for x ≤ 0.005 and the emergence of the pseudo-cubic (Pm3m) structure for higher niobium contents (for x ≥ 0.0075). On the other hand, Raman spectroscopy reveals the augmentation of the tetragonal phase with niobium content. These observations advocate the crossover from the non-ergodic to ergodic phase with niobium content. The presence of the pseudo-cubic phase (Pm3m), especially for x ≥ 0.0075, does not indicate the existence of the long-range cubic phase; rather, it models the contribution of nano-regions with the tetragonal symmetry as indicated in the Raman measurements. It further suggests that, with the incorporation of niobium, the size polar nano-regions diminish that leads to the crossover from the non-ergodic to ergodic phase. [ABSTRACT FROM AUTHOR]

Pigeonpea (Cajanus cajan), an important food legume crop in the semi-arid regions of the world and the second most important pulse crop in India, has an average crop productivity of 780 kg/ha. The relatively low crop yields may be attributed to non-availability of improved cultivars, poor crop husbandry and exposure to a number of biotic and abiotic stresses in pigeonpea growing regions. Narrow genetic diversity in cultivated germplasm has further hampered the effective utilization of conventional breeding as well as development and utilization of genomic tools, resulting in pigeonpea being often referred to as an ‘orphan crop legume’. To enable genomics-assisted breeding in this crop, the pigeonpea genomics initiative (PGI) was initiated in late 2006 with funding from Indian Council of Agricultural Research under the umbrella of Indo-US agricultural knowledge initiative, which was further expanded with financial support from the US National Science Foundation’s Plant Genome Research Program and the Generation Challenge Program. As a result of the PGI, the last 3 years have witnessed significant progress in development of both genetic as well as genomic resources in this crop through effective collaborations and coordination of genomics activities across several institutes and countries. For instance, 25 mapping populations segregating for a number of biotic and abiotic stresses have been developed or are under development. An 11X-genome coverage bacterial artificial chromosome (BAC) library comprising of 69,120 clones have been developed of which 50,000 clones were end sequenced to generate 87,590 BAC-end sequences (BESs). About 10,000 expressed sequence tags (ESTs) from Sanger sequencing and ca. 2 million short ESTs by 454/FLX sequencing have been generated. A variety of molecular markers have been developed from BESs, microsatellite or simple sequence repeat (SSR)-enriched libraries and mining of ESTs and genomic amplicon sequencing. Of about 21,000 SSRs identified, 6,698 SSRs are under analysis along with 670 orthologous genes using a GoldenGate SNP (single nucleotide polymorphism) genotyping platform, with large scale SNP discovery using Solexa, a next generation sequencing technology, is in progress. Similarly a diversity array technology array comprising of ca. 15,000 features has been developed. In addition, >600 unique nucleotide binding site (NBS) domain containing members of the NBS-leucine rich repeat disease resistance homologs were cloned in pigeonpea; 960 BACs containing these sequences were identified by filter hybridization, BES physical maps developed using high information content fingerprinting. To enrich the genomic resources further, sequenced soybean genome is being analyzed to establish the anchor points between pigeonpea and soybean genomes. In addition, Solexa sequencing is being used to explore the feasibility of generating whole genome sequence. In summary, the collaborative efforts of several research groups under the umbrella of PGI are making significant progress in improving molecular tools in pigeonpea and should significantly benefit pigeonpea genetics and breeding. As these efforts come to fruition, and expanded (depending on funding), pigeonpea would move from an ‘orphan legume crop’ to one where genomics-assisted breeding approaches for a sustainable crop improvement are routine.

Vanadium–tellurite glasses, tetragonal TeO2 and orthorhombic V2O5 crystalline samples were characterized for their atomic structure properties by synchrotron X‐ray diffraction, pair distribution function analysis, reverse Monte Carlo simulations (RMC) and Rietveld analysis. The pair correlation function, G(r), of V2O5 shows the first peak at 1.61 Å. G(r) of TeO2 shows three peaks at 1.57, 2.13 and 2.88 Å due to Te–O linkages of three different lengths, whereas the Te–Te atomic pair correlation shows a peak at 3.85 Å. The average coordination number of V with O in crystalline V2O5 is 4.39 while that of Te with O in crystalline TeO2 is 3.71. G(r) of the vanadium tellurite glass shows the first peak at 1.90 Å due to overlapping Te–O and V–O atomic pair correlations. The RMC analysis on diffraction data of glasses found that the V–O coordination number is in the range 5.27–5.59 and the Te–O coordination number is 5.39–5.67. However, it is found that these coordination numbers cannot be clearly defined due to short‐range disorder. [ABSTRACT FROM AUTHOR]

This article was originally published online on 28 July 2023 without the affiliation for author Vasant Sathe. Publisher's note: "Structural evaluation in vicinity of composition induced non-ergodic to ergodic crossover in niobium doped (Na0.41K0.09Bi0.5)TiO3" [J. Appl. Phys. All footnote identifiers and affiliations are correct as they appear above. [Extracted from the article]

The microstructure and residual stress are investigated in W/B4C x-ray multilayer (ML) mirrors as a function of the number of layer pairs (N) varying from 20 to 400 at a fixed period, d ≈ 1.9 nm. The microstructure is analyzed using the x-ray reflectivity (XRR) and rocking scan methods. The total residual stress in the ML film is derived using the substrate curvature measurement method, whereas the stress in W layers of MLs is separately determined by grazing incidence x-ray diffraction measurements based on the sin2 χ method using synchrotron. The successive order Bragg peaks in XRR measured curves indicate good quality of the ML structure in terms of interface roughness and thickness errors. As N increases, the interface width of B4C and W varies in the range of 0.15–0.22 nm and 0.26–0.44 nm, respectively. The contribution of physical roughness to the interface width is significantly lower (∼sub-angstrom) compared to interfacial diffuseness (angstrom level) along with a small (few nanometers) correlation length in the ML structures as observed by rocking scan measurements. The residual stresses both in the W layers and in the ML film are compressive in nature. The total stress in the ML film decreases from −1.444 GPa to −0.389 GPa with increasing N. Measured residual stress in the ML film and W layers is correlated considering a net combined tensile stress arising from B4C layers and interfaces. The ML film with N = 400 shows the least residual stress and is suitable for large layer pair ML optics. Microstructure and stress are correlated considering the mechanism of film growth at the early stage and is discussed. [ABSTRACT FROM AUTHOR]

In this report, the effect of rare-earth (RE3+) ion substitution on structural, microstructural, and electrical properties in barium bismuth titanate (BaBi4Ti4O15) (BBTO) Aurivillius ceramics has been investigated. The Rietveld refinements on X-ray diffraction (XRD) patterns confirm that all the samples have an orthorhombic crystal system with A21am space group. Meanwhile, temperature dependent synchrotron XRD patterns reveal that the existence of dual phase in higher temperature region. The randomly oriented plate-like grains are experimentally strived to confirm the distinctive feature of bismuth layered Aurivillius ceramics. The broad band dielectric spectroscopic investigation signifies a shifting of ferroelectric phase transition (Tm) towards low temperature region with a decrease of the RE3+-ionic radii in BBTO ceramics. The origin of diffuse ferroelectric phase transitions followed by stabilization of the relaxor ferroelectric nature at high frequency region is explained using suitable standard models. The temperature dependent ac and dc conductivity results indicate the presence of double ionized oxygen vacancies in BBTO ceramics, whereas the dominance of single ionized oxygen vacancies is observed in RE-substituted BBTO ceramics. The room temperature polarization vs. electric field (P–E) hysteresis loops are shown to be well-shaped symmetric for BBTO ceramics, whereas slim asymmetric ferroelectric characteristics developed at RE-substituted BBTO ceramics. [ABSTRACT FROM AUTHOR]

The plasmonic responses of silver nanoparticle grating structures of different periods made on silver halide based electron microscope film are investigated. Raster scan of the conventional scanning electron microscope (SEM) is used to carry out electron beam lithography for fabricating the plasmonic nanoparticle grating (PNG) structures. Morphological characterization of the PNG structures, carried out by the SEM and the atomic force microscope, indicates that the depth of the groove decreases with a decrease in the grating period. Elemental characterization performed by the energy dispersive spectroscopy and the x-ray diffraction shows the presence of nanoparticles of silver in the PNG grating. The optical characterization of the gratings shows that the localized surface plasmon resonance peak shifts from 366 to 378 nm and broadens with a decrease in grating period from 10 to 2.5 μm. The surface enhanced Raman spectroscopy of the Rhodamine-6G dye coated PNG structure shows the maximum enhancement by two orders of magnitude in comparison to the randomly distributed silver nanoparticles having similar size and shape as the PNG structure. [ABSTRACT FROM AUTHOR]