Incongruent vaporization of AgNbO3

The high-temperature behavior of AgNbO3 is an important aspect of its processing for applications as a dielectric material. We have studied the AgNbO3 decomposition reaction by simultaneous differential thermal analysis/thermogravimetric analysis (DTA/TGA) at p(total) = 0.1 MPa, and by vacuum thermogravimetry at p(total) = 2.7 mPa. The DTA/TGA results indicate a decomposition temperature of approximate to 860 degrees C at PO2 = 0.1 kPa. From x-ray analysis of the products of vacuum thermogravimetry experiments over the range 650 degrees C to 800 degrees C, we conclude that the decomposition reaction is: 52 AgNbO3(S) -> 2 Ag8Nb26O69(s) + 36 Ag(s) + 9 O-2(g). The incongruent vaporization of AgNbO3 must be taken into account for applications in low-temperature co-fired ceramic (LTCC) materials, typically processed at 800 degrees C to 900 degrees C, if low oxygen pressures are employed during processing.