New dielectric material system of xLa(Mg1/2Ti1/2)O3-(1 - x)Ca0.8Sr0.2TiO3 at microwave frequency

Research highlights: → It is found that xLa(Mg1/2Ti1/2)O3-(1 - x)Ca0.8Sr0.2TiO3 ceramics can be sintered at 1400 deg. C, due to the liquid phase effect of B2O3 addition. → At 1425 deg. C, 0.87La(Mg1/2Ti1/2)O3-0.13Ca0.8Sr0.2TiO3 ceramics with 0.5 wt.% B2O3 addition possesses a dielectric constant (εr) of 38.3, a Q x f value of 59,800 (at 8 GHz) and a temperature coefficients of resonant frequency (τf) of 0 ppm/deg. C. → As the content of La(Mg1/2Ti1/2)O3 increases, the highest Q x f value of 67,000 (GHz) for x = 0.87 is achieved at the sintering temperature 1475 deg. C. → Energy dispersive X-ray (EDX) analysis was used in combination with backscattering electron image (BEI, ) to distinguish each grain of 0.5 wt% B2O3-doped 0.87La(Mg1/2Ti1/2)O3-0.13Ca0.8Sr0.2TiO3 ceramics sintered at 1475 deg. C. From the EDX analysis, the EDX datum of spots A and B was shown in . The grain morphology of 0.5 wt% B2O3-doped 0.87La(Mg1/2Ti1/2)O3-0.13Ca0.8Sr0.2TiO3 ceramics exhibited one types of grains (solid-solution): small cubic-shape grains (spots A) were La(Mg1/2Ti1/2)O3-Ca0.8Sr0.2TiO3 solid-solution and large grains (spot B) were La(Mg1/2Ti1/2)O3-Ca0.8Sr0.2TiO3 solid-solution. As can be seen, all the grains contain a small amount of B indicating the liquid phase will residual inside the grains at the final stage of sintering. - Abstract: The crystal structures, phase compositions and the microwave dielectric properties of the xLa(Mg1/2Ti1/2)O3-(1 - x)Ca0.8Sr0.2TiO3 composites prepared by the conventional solid state route have been investigated. The formation of solid solution is confirmed by the XRD patterns. Doping with B2O3 (0.5 wt.%) can effectively promote the densification and the dielectric properties of xLa(Mg1/2Ti1/2)O3-(1 - x)Ca0.8Sr0.2TiO3 ceramics. It is found that xLa(Mg1/2Ti1/2)O3-(1 - x)Ca0.8Sr0.2TiO3 ceramics can be sintered at 1400 deg. C, due to the liquid phase effect of B2O3 addition. At 1425 deg. C, 0.87La(Mg1/2Ti1/2)O3-0.13Ca0.8Sr0.2TiO3 ceramics with 0.5 wt.% B2O3 addition possesses a dielectric constant (εr) of 38.3, a Q x f value of 59,800 (at 8 GHz) and a temperature coefficients of resonant frequency (τf) of 0 ppm/deg. C. As the content of La(Mg1/2Ti1/2)O3 increases, the highest Q x f value of 67,000 (GHz) for x = 0.87 is achieved at the sintering temperature 1475 deg. C.