Low dielectric loss ceramics in the Mg4Nb2O9-ZnAl2O4-TiO2 ternary system

•The development of crystalline phases and microstructures of Mg4Nb2O9-ZnAl2O4-TiO2 dielectric ceramics was investigated.•The synergistic effect of ZnAl2O4-TiO2 co-doping promoted the Mg4Nb2O9 ceramic densification.•The long-range order on the NbO6 octahedra was enhanced by co-doping ZnAl2O4 and TiO2 to Mg4Nb2O9.•A dielectric constant of 13.1 and a high Qxf value of 366,000 GHz could be obtained for 0.7Mg4Nb2O9−0.15ZnAl2O4−0.15TiO2.