Effects of Chemical Compositions on Electrical Properties of Low Temperature Co-fired Alumina Ceramics with Built-in Silver Electrodes

Abstract

Recent studies by the authors have been intended to develop sintering additives that can make alumina sintered at low temperature with a small quantity. In the case of use of CuO-TiO 2-Nb 2 O 5-Ag 2 O type additives, high-density alumina was obtained by firing at a temperature of 900℃ or below, even though additives content was only 5mass%. In this study, co-firing of above materials with Ag-electrodes at 900℃ or below was examined in order to clarify the relationship between chemical compositions and their reactivity. The results showed that reactivity was highly affected by the Ag 2 O content in the sintering additives. When the content of Ag 2 O was higher, any disappearance of Ag-electrodes was not found and electric properties were almost the same as those of conventional LTCC materials. Finally, these results indicated the obtained materials had possibility to be applied to LTCC modules having high thermal conductivity.

Examination of non‐shrinkage firing using low‐temperature co‐fired alumina containing a small quantity of Cu–Ti–Nb–Ag–O additive

“…Yet, through the addition of 5-10 mass% of a CuO-TiO 2 -Nb 2 O 5 additive, densification at a low temperature of 950-1000°C, which is lower than the melting point of Ag, has been shown to be possible. 18 These results demonstrated the feasibility of the developed material as a LTCC device with high thermal conductivity. A previous study showed that the obtained material exhibited high thermal conductivity of 18 W/mK, exceeding the values of conventional LTCC materials.…”

“…When the content of Ag 2 O was higher, any disappearance of Ag electrodes was not observed, and the electrical properties were nearly the same as those of conventional LTCC materials. 18 These results demonstrated the feasibility of the developed material as a LTCC device with high thermal conductivity. We call the aforementioned alumina material containing the additive of CuO-TiO 2 -Nb 2 O 5 -Ag 2 O (hereinafter abbreviated as Cu-Ti-Nb-Ag-O) as low-temperature co-fired alumina (LTCA).…”

“…(wt% ratio), which was able to be co-fired with Ag electrodes in the previous study. 18 The powders were intermixed using a ball mill for 16 hours utilizing water as a dispersion medium. Then, an LTCA powder was prepared using two types of drying methods (normal heat and freeze drying).…”

Improvement of Sintering Performances and Dielectric Properties of Oriented TiO₂ Ceramics Using Sintering Additives

“…For additive-free samples, needle-like TiO2 particles (FTL-300, Ishihara Sangyo Co., Ltd.), which are elongated along the c-axis, were pulverized in a ball mill for 0, 6, 24, and 72 h and dried. For preparing samples with sintering additives, 95 mass% of the TiO2 particles were mixed with 5 mass% of CuO-TiO2-Nb2O5-Ag2O type oxides, which were found to be effective in sintering of the alumina at low temperatures according to our previous studies [9][10]. The mixture was pulverized for 6 h. Subsequently, oriented ceramics were fabricated using the above-mentioned OCAP method.…”

Sintering mechanism of low‐temperature co‐fired alumina featuring superior thermal conductivity

“…It is slightly lower than the 22 W/mK for alumina with additive "B," but this material is not a LTCC as it cannot be co-fired with Ag metals owing to the significant reaction between them. 19 The thermal conductivity of polycrystalline ceramics at saturation density is affected by the grain size and grain boundaries, because a larger grain size reduces phonon scattering at the grain boundaries. When alumina with additive "A" was sintered at 900, 950, or 1000°C (temperatures at which liquid phases form) for 24 hours, 20 the sintered density was approximately 3.9 g/cm 3 .…”