Low Temperature Sintering of Alumina by CuO-TiO₂-Nb₂O₅ Additives

Abstract

We examined sintering additives for alumina. When using CuO-TiO2-Nb2O5 additive, dense sintered alumina was obtained by firing at 1000°C or below, even though additive content was at most 10 mass%. It is considered that the formation of mixed oxide consists of CuO, TiO2 and Nb2O5 has an important role for low temperature sintering of alumina. Thermal conductivity of the above sample was 15 W/mK, which was the highest value yet reported within LTCC (Low Temperature Co-fired Ceramics) materials.

Preparation and Characterization of Low Temperature Sintered Alumina by CuO-TiO2-Nb2O5-Ag2O Additives

“…In order to examine the difference in the generated phases by the sintering additives near the firing temperature, powder X-ray diffraction analysis was performed on each sintering additive treated at 750 ∼ 980 • C. The change of generated compounds by the heat-treated temperature of additive A and C is shown respectively in Figs. 5 and 6, and the generated compounds after treating at 850 • C are shown in Table 1 CuNb 2 O 6 , CuTi 2 Nb 2 O 10 and CuO at 850 • C, but these compounds disappear with the increased treatment temperature and produces the composite compound Cu 4 TiNb 4 O x , which promotes alumina sintering, in almost a single phase at 900 • C and higher [5]. On the other hand, sintering additive C, which contains 34.8mol% of Ag 2 O, produces primarily AgNbO 3 and CuO at 750 • C, but these compounds decrease as the treatment temperature rises, and produces the compound (called Cu 4 TiNb 4 O x solid solution), which has the same diffraction pattern as Cu 4 TiNb 4 O x at 800 • C and higher.…”

“…As the first step of producing high-frequency modules having a thermal conductivity and physical strength as high as that of alumina, the authors have developed the sintering additives that enable low-temperature sintering by mixing in a small quantity. The previous studies [3,4] [5]. The study has also identified that the best sintering performance is obtained with the combination of the three-element components CuO: The combined powder was mixed in a ball mill for 24 hours by using water as a diffusion medium.…”

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

“…[10][11][12][13][14][15][16] Sintering additives based on Cu 2 O-TiO 2 , CuO-TiO 2 , and MnO-TiO 2 have been previously examined. [10][11][12][13][14][15][16] Sintering additives based on Cu 2 O-TiO 2 , CuO-TiO 2 , and MnO-TiO 2 have been previously examined.…”

“…[10][11][12][13][14][15][16] Sintering additives based on Cu 2 O-TiO 2 , CuO-TiO 2 , and MnO-TiO 2 have been previously examined. 15,16 Furthermore, through the use of a CuO-TiO 2 -Nb 2 O 5 -Ag 2 O additive, which is obtained by adding Ag 2 O to the CuO-TiO 2 -Nb 2 O 5 additive, further low-temperature sintering of alumina has been realized. 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.…”

“…First, toward the production of high-frequency-use LTCC modules featuring high thermal conductivity and physical strength similar to those of alumina, many studies have developed sintering additives that enable low-temperature sintering when admixed in small quantities. [10][11][12][13][14][15][16] Sintering additives based on Cu 2 O-TiO 2 , CuO-TiO 2 , and MnO-TiO 2 have been previously examined. [10][11][12][13][14] However, none of these binary composition samples have been shown to exhibit satisfactory sintering performance at temperatures below 1000°C.…”