The development of new ceramics, which are composed of Ba (Zn//1/////3Ta//2/////3)O//3 multiplied by (times) Ba(Zn//1/////3Nb//2/////3) O//3 solid solution, for microwave devices are reported. These ceramics have a large dielectric constant epsilon //r of 30-40, a loss quality factor Q of 15000, and a temperature coefficient of resonant frequency tau //f of 0-28 ppm/ degree C (variable by changing the composition). The use of these ceramics as resonant elements of filters and stabilized oscillators, and also as substrate of microwave integrated circuits is examined.