National Association of Development Organizations

In this work, Zn co-doped tungsten bronze having nominal formula Ba5CaTi1.94Zn0.06Nb8O30 has been synthesized and systematically studied for structure, dielectric and electrical properties. The formation of the phase of tetragonal tungsten bronze with space group P4bm and the occurrence of oxygen vacancies were verified by the Rietveld refinement using X-ray diffraction data. Scanning electron microscopy (SEM) of Ba5CaTi1.94Zn0.06Nb8O30 ceramic shows high densification, low porosity, and homogeneous distribution of grains of different sizes over the total surface. The sample shows a dielectric anomaly of ferroelectric paraelectric type at 262 °C, and has non-relaxor type of diffuse phase transition. The electrical property (complex impedance Z*, complex permittivity ε*, complex modulus M*) of Ba5CaTi1.94Zn0.06Nb8O30 ceramic has been investigated by non-destructive complex impedance spectroscopy (CIS) as a function of frequency at different temperatures. Grains and grain boundaries conduction is detected from a complex impedance spectrum by fitting the Nyquist plot with an appropriate electrical circuit. The Nyquist plot indicates the negative temperature coefficient of resistance (NTCR) character of Ba5CaTi1.94Zn0.06Nb8O30 ceramic. The variation of AC conductivity as a function of frequency reveals that the compound has an Arrhenius-type behavior of electrical conductivity. The DC electrical conductivities of grains and grain boundaries have been studied. The presence of non-Debye relaxations was verified by a complex modulus analysis.


 
 
 
 El propósito de este artículo, reside en mostrar y analizar, las metáforas más notables con las cuales el maestro dominico de vida espiritual Eckhart, transmite la reunión del alma humana creada y separada (existente) del Dios Creador, con lo Uno, o unidad esencial originaria, definida en su totalidad como Deidad. La atención se centra en alguno de sus sermones, donde se explican las alegorías del alma humana, la divinidad y la fusión o encuentro de ambas en la Deidad. Se trata de un recorrido interpretativo por elementos centrales y alegóricos de su mística nihilista y de su teología negativa, donde la única y última conclusión sostenible es que “Todo se hace Nada”.
 
 
 
 

Polystyrene/graphene oxide (PSt/GO) nanocomposite latexes have been prepared by Pickering miniemulsion polymerization in the presence of the conventional surfactant sodium dodecyl sulfate (SDS) in order to investigate its influence on the polymerization mechanism.