Sintering and dielectric properties of Al2O3 ceramics doped by TiO2 and CuO

Abstract

The effects of CuO and TiO 2 additives on the microstructure and microwave dielectric properties of Al 2 O 3 ceramics were investigated. Al 2 O 3 ceramics with CuO and TiO 2 additions can be well sintered to achieve 93∼98% theoretical densities below 1,360°C due to Ti 4 Cu 2 O liquid phase sintering effect. The Qf values decreased with increasing CuO and TiO 2 content, due to the formation of the second phase Ti 4 Cu 2 O. However, the varying behaviors of the dielectric constant (ɛ r ) and temperature coefficients (t f ) were associated with phase constitutions, as a result of the change of CuO and TiO 2 content. The t f can be shifted close to 0 ppm/°C by controlling the content of CuO and TiO 2 . The specimens with 0.5 wt.% CuO and 7 wt.% TiO 2 sintered at 1,360°C for 4 h showed ɛ r of 11.8, Qf value of 30,000 GHz, and t f of −7 ppm/°C.

Experimental determination of the eutectic temperature in air of the CuO–TiO2 pseudobinary system

“…A small amount of TÍO2 is added to metal Cu for the formation of large CuO crystals. 5 Novel materials based in the CaO-CuO-Ti0 2 system, CaCu 3 Ti 4 0i 2 (CCTO) has recently attracted much interest due to its giant dielectric constant (up to 10 5 ) which is almost frequency independent and shows good temperature stability in the range between 100 and 400 K. 6 Recently Jacob et al 7 ' 8 have determined the heat capacity of CCTO and the phase diagram for the pseudoternary system CaO-Ti0 2 -CuO/Cu 2 0 at 1000 °C as a function of oxygen partial pressure, without point to the presence of liquid phase except when the CCTO decomposed at ~1167°C in Ti0 2 , CaTi0 3 and a liquid phase rich in CU2O. Veith et al 9 have determined the phase relationship in the ternary system CuO-Ti02-CaO at 950 °C in air where the copper oxide transforms into a liquid phase during the sintering treatment and leads to anomalous grain growth.…”

Sintering behavior of Y‐doped BaZrO3 refractory with TiO2 additive and effects of its dissolution on titanium melts

“…Doping 1 mol% TiO 2 additive into BaZr 0.9 Y 0.1 O 3−δ , the relative density has been improved remarkedly to 91% at 1720°C . At the same time, sintering performance was improved drastically by the addition of sintering aid TiO 2 in Al 2 O 3 ceramic . However, the effects of TiO 2 additive into Y‐doped BaZrO 3 and the interface reaction between Y‐doped BaZrO 3 crucible and titanium‐rich alloys have not been reported.…”

Low-temperature Sintering Mechanism, Dielectric, and Thermal Properties of CuO-TiO₂-Nb₂O₅-containing Al₂O₃ Ceramics Featuring Superior Thermal Conductivity

“…As a first step toward the production of highfrequency-use LTCC modules featuring high thermal conductivity and physical strength, similar to those of pure alumina, many researchers have developed sintering additives that could enable low-temperature sintering when admixed in small quantities [10][11][12][13][14][15]. Sintering additives based on Cu2O-TiO2, CuO-TiO2, and MnO-TiO2 have been previously researched [10][11][12][13]. However, none of these binary composition additives have been determined to exhibit satisfactory sintering performances at temperatures below 1000 °C.…”