Editor's message: beaming energy from the space

Our society is consuming energy figures which are so large that sometimes they become meaningless when mentioned; electricity alone in 2012 was 20,900 TWH (IEA World energy statistics), 68% from fossil fuels, 11% nuclear and 21% ‘renewable’; the energy that comes from resources that are not significantly depleted by their use, such as sunlight, wind, rain, tides, waves and geothermal heat. It is estimated that energy consumed in the buildings (residential and commercial end users) accounts for 20.1% of this total ([International Energy Outlook 2016). Losses are not considered here, but they are not negligible, either

Sintering of MLCC’S barium titanate with microwaves

[EN] A comparison of microwave and conventional, in an electric resistance furnace, sintered layers of dielectric base barium titanate (BaTiO3) of the kind employed for multilayer ceramic capacitors (MLCC) was performed. Two kinds of samples were used for each processing method; the layers alone without electrodes, and the green MLCC with the layers and electrodes interdigitated. Samples were exposed to microwaves for 20 minutes and heated up to 1050°C and 1150°C for sintering in a crucible with graphite that acted as reduction agent and microwave susceptor. Conventional sintering was performed in the same arrangement but lasted 120 minutes since it was found that 20 minutes was not enough time to achieve sintering. Heating rate in both cases was 10 °C/min. It was observed that the layers without the electrodes achieve about the same densification for both processes, while in the case of the green MLCC’s the results were variable, ranging from sample that became dust, to cracked samples and some well sintered ones. At least in the microwave case, it is possible that the variability of the results is due to the importance of the location of the sample in the cavity that in turn affects the electric field pattern, especially because the presence of the electrodes that can cause overheating around them.Aguilar-Garib, J.; Tijerina-García, O.; Garza-Guajardo, J. (2019). Sintering of MLCC’S barium titanate with microwaves. En AMPERE 2019. 17th International Conference on Microwave and High Frequency Heating. Editorial Universitat Politècnica de València. 457-462. https://doi.org/10.4995/AMPERE2019.2019.9919OCS45746

Suspensiones de BaTiO3 para la fabricación de cintas dieléctricas para capacitores

Una de las técnicas más populares para la fabricación de capacitores multicapa (MLCC en inglés) es el vaciado en cinta, el cual requiere la preparación de una suspensión acuosa o no acuosa. Hay poca información disponible en la literatura en referencia sobre comparaciones directas de sistemas acuosos y no acuosos utilizando suspensiones de BaTiO3 para cintas dieléctricas de menos de 3.5 m de espesor. Por lo tanto en este trabajo se consideran ambos tipos de suspensiones con el propósito de sopesar los diferentes factores que influyen en la viscosidad de la suspensión y el espesor de la cinta cerámica. Se encontró que la adhesión sustrato-cinta juega un papel importante sobre el adelgazamiento en composiciones basadas en agua. La viscosidad de la suspensión está definida por el tipo de dispersante en sistemas acuosos y del ligante en los no acuosos

Formulación de una barbotina para producir cintas cerámicas ultradelgadas

Se diseñó una barbotina cuyo comportamiento viscoelástico resulta óptimo para obtener cintas cerámicas a base de BaTiO3 de 3 μm mediante “tape casting”. Se demuestra que el módulo elástico de la viscoelasticidad es relevante en el espesor final de la cinta. Estas cintas se utilizan regularmente en la industria de los capacitores cerámicos multicapas, y se considera en la industria en general que el espesor mínimo que se puede obtener mediante “tape casting” es de 3.5 μm, por lo que los resultados de este trabajo corresponderían en estos términos a cintas ultradelgadas. Se encontró que el solvente más adecuado es una mezcla tolueno-etanol, un copolímero graft ABn o fosfato éster como dispersantes, y PVB de peso molecular medio como aglutinante

Recent progress in the shaping and sintering of barium titanate nanoparticles. Application to high permittivity capacitors.

The miniaturisation of electronic components required for many devices involves an increase their volumic efficiency. This work focus on the size reduction of capacitors. They are two ways for increasing the capacity of such passive components. One is to find materials with high permittivity, the other is to reduce the thickness of the films used in multilayers ceramics. Barium titanate, BaTiO3 (BT) nanoparticles were sintered using Spark Plasma Sintering (SPS) because the material presents interesting properties when obtained by SPS [1-3]. In this case, very unusual interesting dielectric properties, a so called “colossal” permittivity value up to several thousands. Moreover, no temperature dependence is observed. However, the values of dielectric losses are too high to consider industrial applications. In order to reduce these dielectric losses, different approaches have been proposed to control the chemistry of grain boundaries. We present here the structural, microstructural and electrical properties of ceramics sintered by SPS from BaTiO3 powders elaborated by co-precipitation method. Different routes tested to improve the dielectric properties of the ceramics are presented and discussed.On the other side, thick films of BT have been prepared. The objective of this work was to develop a BaTiO3 material having an accurate particle size to reduce the thickness of sintered films down to 1 μm. The rheological properties of the slurry have been optimized and, thanks to a suitable tape casting process, homogeneous thin films of 1 μm thickness could be obtained. Some properties of the films are described