Compositional tailoring effect on ZnGa2O4-TiO2 ceramics for tunable microwave dielectric properties.

(1- x)ZnGa 2 O 4 - x TiO 2 (x = 0.05–0.20) composite ceramics were fabricated via traditional solid state method. The experimental and theoretical value of ɛ r , τ f and Q × f shows similar trend. Tunable microwave dielectric performance was achieved due to the effect of TiO 2 , especially for temperature coefficient and quality factor. The large negative temperature coefficient at resonant frequency (τ f) of ZnGa 2 O 4 was continuously tailored from negative (−70 ppm/oC) to positive (+13 ppm/oC) 2 For practical application, 15 mol% (about 6.9 V%) TiO 2 can adjust τ f value to near zero. The tailoring effect on quality factor (Q × f) was significant. Due to the smaller Q × f values of TiO 2 , the Q × f value decreases with the increasing content of TiO 2. The inhomogeneous microstructure results in the increasing difference between calculated and experimented Q × f value. In addition, compositing TiO 2 with ZnGa 2 O 4 ceramic not only promote the grain growth but also reduce its sintering temperature from 1400 °C to 1300 °C. The dielectric constant (ɛ r) was not significant affected by TiO 2 , only varied from 10.8 to 12.7. The ɛ r value of 12.3, Q × f value of 73,000 GHz (at 11.8 GHz) and τ f value of +3 ppm/°C were achieved for 0.85ZnGa 2 O 4 -0.15TiO 2 , sintered at 1300 °C for 2 h. Image 1 • The compositing effect of TiO 2 results in tunable microwave dielectric performance. • The large negative τ f continuously shifts from negative to positive. • Endows ZnGa 2 O 4 -TiO 2 with additional application potential as high quality MDCs. • ZnGa 2 O 4 -TiO 2 provides a good example of rational design to tailor τ f. [ABSTRACT FROM AUTHOR]