A series of (ABi)1/2MoO4 (A=Li, Na, K, Rb, Ag) compositions were studied in regard to the sintering behavior, phase composition, microwave dielectric properties and chemical compatibility with silver and/or aluminum for electrodes. All the (ABi)1/2MoO4 (A=Li, Na, K, Rb, Ag) ceramics could be sintered below 700 oC with high relative density >93%. Whereas the (KBi)1/2MoO4 ceramic can be sintered to a high density at around 630 oC/2hrs with a relative permittivity ~37, a Qf value of 4,000 GHz and a temperature coefficient of resonant frequency (TCF) ~+117 ppm/oC. Furthermore, from the XRD analysis of co-fired ceramics, the (KBi)1/2MoO4 ceramic reacts with silver but not with aluminum at its densification temperature. The (ABi)1/2MoO4 (A=Li, Na, K, Rb, Ag) type ceramics can all be considered into the new field of ultra-low temperature co-firing dielectrics for multilayer applications.

In the present work, a pure monoclinic phase of BaNd2(MoO4)4 and BaSm2(MoO4)4 was formed at 850°C and 600°C, respec- tively, via a solid-state reaction method. The ceramic samples were found to be well densified at 960°C. Dense and homo- geneous microstructures were revealed from the scanning electron microscopy. The microwave dielectric behaviors were studied as a function of sintering temperature and characterized in the temperature range 25°C–120°C. The best properties were obtained in ceramics sintered at 960°C with a permittivity ~11.7, a Q 3 f value of 45 000 GHz and a temperature coeffi- cient of frequency about
41 ppm/°C for BaNd2(MoO4)4 cera- mic at 9.9 GHz, and a permittivity ~11.8, a Q 3 f value of 20 000 GHz, and a temperature coefficient of frequency about
34 ppm/°C for BaSm2(MoO4)4 ceramic at 9.7 GHz, respec- tively.