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Low-sintering condenser materials on the basis of barium titanate; Niedrig-sinternde Kondensatorwerkstoffe auf der Basis von Bariumtitanat

Abstract

The main objective of this work was the development of new barium titanate capacitor materials, which fully densified at a sintering temperature of 900 C and exhibit a high and almost temperature-independent dielectric constant as well as low dielectric loss. In order to decrease the sintering temperature of barium titanate from ca. 1300 C to 900 C, addition of various types of sintering aids have been tested. Li-containing sintering additives show the best result concerning densification and dielectric properties. By addition of 2 to 3 wt% (SrO-B{sub 2}O{sub 3}-Li{sub 2}O) -, (ZnO-B{sub 2}O{sub 3}-Li{sub 2}O) - or (LiF-SrCO{sub 3})-additive combinations to commercially available barium titanate powder 95 % of the theoretical density was achieved after sintering at 900 C. The sintered capacitor materials with the above mentioned additive combinations possess high dielectric constants from 1800 to 3590. It is well known that for a high temperature stability of dielectric constant the formation of core-shell structure in a fine-grained microstructure is required (average grain size < 1 {mu}m). For BaTiO{sub 3} samples contained 2 wt% LiF-SrCO{sub 3} is temperature coefficient of capacitance (TCC) relatively low. The TCC in temperature range between 0 C and 80 C is less than {+-} 15%.  More>>
Publication Date:
Jul 01, 2010
Product Type:
Thesis/Dissertation
Report Number:
ETDE-DE-2791
Resource Relation:
Other Information: TH: Diss. (Dr.-Ing.); Related Information: Series: BAM-Dissertationsreihe|v. 68
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; CAPACITORS; BARIUM OXIDES; TITANIUM COMPOUNDS; ENERGY STORAGE; DIELECTRIC MATERIALS; SINTERING; ADDITIVES; TEMPERATURE DEPENDENCE
OSTI ID:
22008294
Research Organizations:
Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin (Germany); Erlangen-Nuernberg Univ., Erlangen (Germany). Technische Fakultaet
Country of Origin:
Germany
Language:
German
Other Identifying Numbers:
Other: ISBN 978-3-9813853-2-8; ISSN 1613-4249; TRN: DE12GD468
Availability:
Commercial reproduction prohibited. Available from ETDE as OSTI ID: 22008294;
Submitting Site:
DE
Size:
133 page(s)
Announcement Date:
Jan 01, 2013

Citation Formats

Naghib zadeh, Hamid. Low-sintering condenser materials on the basis of barium titanate; Niedrig-sinternde Kondensatorwerkstoffe auf der Basis von Bariumtitanat. Germany: N. p., 2010. Web.
Naghib zadeh, Hamid. Low-sintering condenser materials on the basis of barium titanate; Niedrig-sinternde Kondensatorwerkstoffe auf der Basis von Bariumtitanat. Germany.
Naghib zadeh, Hamid. 2010. "Low-sintering condenser materials on the basis of barium titanate; Niedrig-sinternde Kondensatorwerkstoffe auf der Basis von Bariumtitanat." Germany.
@misc{etde_22008294,
title = {Low-sintering condenser materials on the basis of barium titanate; Niedrig-sinternde Kondensatorwerkstoffe auf der Basis von Bariumtitanat}
author = {Naghib zadeh, Hamid}
abstractNote = {The main objective of this work was the development of new barium titanate capacitor materials, which fully densified at a sintering temperature of 900 C and exhibit a high and almost temperature-independent dielectric constant as well as low dielectric loss. In order to decrease the sintering temperature of barium titanate from ca. 1300 C to 900 C, addition of various types of sintering aids have been tested. Li-containing sintering additives show the best result concerning densification and dielectric properties. By addition of 2 to 3 wt% (SrO-B{sub 2}O{sub 3}-Li{sub 2}O) -, (ZnO-B{sub 2}O{sub 3}-Li{sub 2}O) - or (LiF-SrCO{sub 3})-additive combinations to commercially available barium titanate powder 95 % of the theoretical density was achieved after sintering at 900 C. The sintered capacitor materials with the above mentioned additive combinations possess high dielectric constants from 1800 to 3590. It is well known that for a high temperature stability of dielectric constant the formation of core-shell structure in a fine-grained microstructure is required (average grain size < 1 {mu}m). For BaTiO{sub 3} samples contained 2 wt% LiF-SrCO{sub 3} is temperature coefficient of capacitance (TCC) relatively low. The TCC in temperature range between 0 C and 80 C is less than {+-} 15%. The formation of the core-shell structure in a fine-grained microstructure of this sample, which is required to have low TCC, was detected by TEM / EDX analyses. The significantly higher TCC for the BaTiO{sub 3} samples contained 3 wt% SrO-B{sub 2}O{sub 3}-Li{sub 2}O is due to the strong grain growth during sintering. To reduce the TCC in this sample Nb{sub 2}O{sub 5}-Co{sub 2}O{sub 3} was added. By addition of 1.5 wt% Nb{sub 2}O{sub 5}-Co{sub 2}O{sub 3} the temperature stability of the dielectric constant could be significantly improved as a result of the grain growth inhibition and the core-shell formation during sintering. For BaTiO{sub 3} samples contained ZnO-B{sub 2}O{sub 3}-Li{sub 2}O a fine-grained microstructure was formed which caused the relatively low TCC of this sample. However, the influence of Nb{sub 2}O{sub 5}-Co{sub 2}O{sub 3}-addition on dielectric properties of ZnO-B{sub 2}O{sub 3}-Li{sub 2}O containing BaTiO{sub 3} samples was also investigated. The BaTiO{sub 3} samples contained ZnO-B{sub 2}O{sub 3}-Li{sub 2}O-Nb{sub 2}O{sub 5}-Co{sub 2}O{sub 3} show high dielectric constant up to 2370. The Co{sub 2}O{sub 3}-Nb{sub 2}O{sub 5}-addition would not cause further lowering of TCC because of a strong grain growth during sintering. To reduce the TCC, the grain growth during sintering must be controlled. For this goal the composition of ZnO-B{sub 2}O{sub 3}-Li{sub 2}O was modified. It was found that an increase of B{sub 2}O{sub 3} content or a decrease of Li{sub 2}O and ZnO content in ZnO-B{sub 2}O{sub 3}-Li{sub 2}O additive composition improves the temperature stability of the dielectric constant. The BaTiO{sub 3} ceramics contained modified ZnO-Li{sub 2}O-B{sub 2}O{sub 3} composition and 1.5 wt% Nb{sub 2}O{sub 5}-Co{sub 2}O{sub 3} shows TCC of less than {+-} 15 % over the measured temperature range from - 40 C to +125 C. However, the room temperature dielectric constant also decreases and amounts to 1280. The formation of the core-shell structure in a fine-grained microstructure has been proved in TEM/SEM studies of this sample and it is responsible for the high temperature stability of the dielectric constant. A further objective of this work was to manufacture ceramic tapes from the new capacitor materials and integration of these tapes into multi-component LTCC moduls, i.e. a combination with ferritic tapes and standard low dielectric constant tapes (Basis LTCC). Tapes and laminates from five favoured capacitor materials have been produced. The sintered laminates show significantly higher dielectric constants (up to 3350) and lower dielectric losses ({<=}0,025) in comparison to pressed samples. This is because of lower porosity of the laminates after sintering. The results of the temperature stability of the dielectric constant in powder compacts could be reproduced in multilayer capacitors. Due to very low capacity changes in the frequency range between 1 kHz and 1 MHz all five capacitor materials are applicable at this frequency range. Furthermore the capacitor tapes exhibit high breakdown strength significantly above 20 kV / mm (except one sample). To reach a defect free co-firing of sandwiched LTCC laminates consisting of capacitor tapes and standard low dielectric constant tapes the shrinkage behaviour and the coefficient of thermal expansion of two components were matched. The embedded capacitor tapes into standard low dielectric constant tapes can be sufficiently densified during co-firing process at 900 C and the dielectric properties are comparable with those of separate sintered capacitor tapes. The co-firing of multi-component LTCC laminates consisting of ferritic tapes, low dielectric constant tapes and capacitor tapes with different shrinkage curves was also investigated. It was found that the manufacturing of such a multi-component module is only possible when a uniaxial pressure (1.5 MPa) is carried out during co-firing. However, because of the difference in the coefficient of thermal expansion of different components, a quite defectfree multi-component module could not be manufactured but by stacking the tapes in the correct order defects like cracks can be strongly minimized. For this purpose the capacitor tapes that have larger coefficient of thermal expansion must be inserted in the middle of the multi-component laminates. The results obtained in this work are very useful for the integration of passive components into compacted LTCC module and the further miniaturization of electronic devices based on ceramic multilayer. The new low fired high dielectric constant materials can be used both as ceramic tapes and as screen-printable pastes for integration of capacitors into LTCC modules.}
place = {Germany}
year = {2010}
month = {Jul}
}