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Papers by Jacob Hormadaly

Published in 2012 in Cambridge UK Philadelphia by Woodhead Publishing, 2012

ABSTRACT Co_2SnO4 is a cubic (space group Fd\=3m) II-IV inverse spinel with one Co^2+ ion on the ... more ABSTRACT Co_2SnO4 is a cubic (space group Fd\=3m) II-IV inverse spinel with one Co^2+ ion on the A site and the other on the B site. The result of Rietveld refinement of neutron powder diffraction data demonstrates that the atomic inversion is almost complete. High temperature magnetic susceptibility measurements show this material to be a Curie paramagnet with an average Co magnetic moment of 4.8 mu _B, consistent with spin 3/2 Co^2+ ions on both (tetrahedral) A and (octahedral) B sites (and Sn^4+ ions on the B sites). At a temperature of 40 K short range magnetic order develops, leading to a state with a saturated moment of 2.5 mu B in a 5.4 T magnetic field. Upon cooling below 40 K the remanence and coercivity first increase and then, at temperatures below 30 K, decrease, consistent with progressive magnetic compensation of the A and B sublattices. In this contribution we will describe the results of synchrotron x-ray and neutron powder diffraction measurements which provide information about the atomic and magnetic order in Co_2SnO_4.

Journal of Non-Crystalline Solids, 2021

Abstract Pellets and substrates made from powders of Pyrex-type and soda lime glasses and alkalin... more Abstract Pellets and substrates made from powders of Pyrex-type and soda lime glasses and alkaline earth carbonates were prepared and sintered in the 625-850C range. Powder preparation, sintering temperature, alkaline earth carbonate concentration, acid leaching of alkaline earth carbonate after sintering and effects of time on pellets' integrities after sintering were studied. Densities and porosities of pellets after acid leaching were estimated from pellet's dimensions and weight. CaCO3 behaves in a different way from SrCO3 and BaCO3. Pellets made with CaCO3 break after sintering for the majority of sintering temperatures studied. A mechanism for pellets' breakage based on XRD studies is proposed and discussed. A procedure based on the new mechanism was implemented successfully to prevent breakage after sintering.

$Research paper thumbnail of Crystal structure of Nd2−xMxRu2O7−y (M=Cu, Ag) pyrochlores by X-ray powder diffraction$

Powder Diffraction, 2007

The crystal structures of ruthenium oxides with the general formula Nd2−xMxRu2O7−y, where M is Cu... more The crystal structures of ruthenium oxides with the general formula Nd2−xMxRu2O7−y, where M is Cu or Ag, 0≤x≤0.25, were investigated. All compounds that were prepared exhibit the pyrochlore structure with a cubic unit cell. The compounds were characterized by X-ray powder diffraction, and single-phase structures were found for Nd2−xCuxRu2O7−y, x=0.1, 0.2, 0.25, and for Nd2−xAgxRu2O7−y, x=0.1, 0.15, 0.2. The relative metal concentrations were verified by EDS. The cell parameters were determined by advanced peak-position analysis and calibrated by a Si internal standard. Atomic positions and oxygen occupancies where refined by the Rietveld method. It was found that the cell-size modifications agree with the relations between ionic sizes.

Printed Films, 2012

Abstract: The terms ‘printed electronics’ and ‘direct-write deposition’ are increasingly familiar... more Abstract: The terms ‘printed electronics’ and ‘direct-write deposition’ are increasingly familiar to manufacturers and consumers of electronic products. The trend is to make use of new cost-efficient ways to mass-produce electronic devices and in prospective to open new huge product markets. There are already several applications of functional printed films, but further improvements in performance/cost ratios are envisaged, especially in ‘organic electronics’ and ‘flexible’ products. Development in these fields is progressing rapidly on several parallel paths, each with its own strengths and limitations. In this chapter, a broad overview of technologies capable of printing functional films for the microelectronic and electrical industries is presented. First, the history of the most mature and traditional print process known as ‘screen printing’ is delineated and the steps that have resulted in improved, increasingly integrated systems and diversified materials are retraced. Motivations for ever-increasing resolutions are then approached and technologies on which current research is mainly focused are briefly outlined.

Journal of Solid State Chemistry, 1975

Journal of Solid State Chemistry, 1980

Journal of Non-Crystalline Solids, 2008

Journal of Non-Crystalline Solids, 1978

ABSTRACT Absorption spectra of Ho3+ in germanate glasses were measured in the range 300–2500 nm a... more ABSTRACT Absorption spectra of Ho3+ in germanate glasses were measured in the range 300–2500 nm and the intensity parameters were calculated by the Judd-Ofelt theory. Excitation and emission spectra were measured in the visible at a temperature range of 80–573 K. The radiative transition probabilities from the excited states [5F4, 5S2], 5F5, 5I4, 5I5 and 5I6, branching ratios and integrated emission cross-sections were calculated. The non-radiative relaxation rate from the (5F4, 5S2) levels is estimated to be about 2 × 105 s−1.

Journal of Non-Crystalline Solids, 2011

Journal of Non-Crystalline Solids, 2005

Journal of Non-Crystalline Solids, 2010

Journal of Non-Crystalline Solids, 1979

ABSTRACT Intensity parameters () of Pr3+ and Dy3+ have been obtained in tellurite, borate and pho... more ABSTRACT Intensity parameters () of Pr3+ and Dy3+ have been obtained in tellurite, borate and phosphate glasses. It has been found that calculated by exlusion of hypersensitive transitions, gives a better fit between measured and calculated lifetimes and branching ratios than those including hypersensitive transitions. Using these parameters and calculated matrix elements U(Λ), radiative transition probabilities, branching ratios and integrated cross sections for stimulated emission were calculated for 3P0, 3P1 and 1D2 excited states of Pr3+ and excited state of Dy3+. Potential transitions are indicated.

Journal of Materials Science: Materials in Electronics, 2006

Lead-free thick film resistive compositions suitable for hybrid microelectronics were prepared. T... more Lead-free thick film resistive compositions suitable for hybrid microelectronics were prepared. The compositions were made with RuO 2 as the conducting phase and bismuthate glasses. This blend of bismuthate glasses constitutes a suitable choice for avoiding negative effects such as devitrification, bleeding out of the glass on alumina substrates, anomalous distribution of conductive grains in the glassy matrix and phase separation observed in other systems. The morphology, microstructure and electrical properties have been studied. X-ray diffraction (XRD), electron scanning microscopy (SEM) and energy dispersion spectroscopy (EDS) show that a defect pyrochlore phase of bismuth titanate formed at about 700 °C in all the compositions studied. Transmission electron microscopy (TEM) analysis of the original RuO 2 powder shows that a single grain is made of many smaller grains of different crystalline orientations. The sheet resistance spans two decades by changing the RuO 2 fraction from about 14-52 wt%. The resistors exhibit good reproducibility and their temperature coefficient of resistance is in the range of ± 300 ppm/°C. Three resistor compositions denoted as JH024/3, JH024/4 and JH024/5 were the subject of this study.