Structure and microwave dielectric characteristics of Hf1-xTixO2 ceramics

Hf1-xTixO2 dense ceramics were prepared by a standard solid-state reaction process, and the microwave dielectric properties in a wide frequency range were determined together with structure evolution. With increasing x, the structure gradually changed from HfO2-based solid solution (monoclinic in space group P2(1)/c, x <= 0.05) to HfTiO4 (orthorhombic in space group Pbcn, x = 0.5), and the two phase regions were determined for 0.1 <= x x = 0.55. The microwave dielectric properties of HfO2 ceramics at 10 GHz were determined as epsilon(r) = 14, Qf = 24 500 GHz, tau(f) = -50 ppm/celcius. With Ti-substitution, the microwave dielectric characteristics, especially the Qf value, could be significantly improved, and the best combination of microwave dielectric characteristics was achieved at x = 0.05: epsilon(r) = 17, Qf = 84 020 GHz (at 7.8 GHz) and 151 260 GHz (at 27.9 GHz), and tau(f) = -47 ppm/celcius. The smallest temperature coefficient of resonance frequency (tau(f) = -4.8 ppm/celcius) was obtained for x = 0.55 together with a Qf value of 52 370 GHz at 5.0 GHz and 60 390 GHz at 17.9 GHz, where the dielectric constant was 40. Moreover, Hf1-xTixO2 microwave dielectric ceramics might be very competitive in the future of mobile communication technology due to their excellent compatibility with Si.

Automated summary

Hf1-xTixO2 dense ceramics were prepared using a standard solid-state reaction process, and their microwave dielectric properties were significantly improved with Ti substitution, especially achieving the best combination at x = 0.05. The sample with x = 0.55 had the smallest temperature coefficient of resonance frequency, providing potential competitiveness in future mobile communication technology due to excellent compatibility with Si.