A new group of compounds with composition (Ba5-xSrx)Nb4O15, having hig
h permittivity and low loss have been prepared and characterised in th
e microwave frequency region. X-ray diffraction studies showed that mo
nophase compound existed for all values of x from 0 to 5. Microwave di
electric properties such as epsilon(r) and tau(f) showed smooth variat
ion with x, while the unloaded quality factor (Q(u)) showed remarkable
improvement with x. A range of ceramic dielectric resonators(DR) with
40< epsilon(r) <50,-10<tau(f)<+10 and Q x f>10,000 can be obtained in
this system.