Structure and microwave dielectric characteristics of Hf1‐xTixO2 ceramics

Abstract

AbstractHf1‐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 P21/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 < 0.5 and x = 0.55. The microwave dielectric properties of HfO2 ceramics at 10 GHz were determined as εr = 14, Qf = 24 500 GHz, τf = –50 ppm/℃. 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: εr = 17, Qf = 84 020 GHz (at 7.8 GHz) and 151 260 GHz (at 27.9 GHz), and τf = –47 ppm/℃. The smallest temperature coefficient of resonance frequency (τf = –4.8 ppm/℃) 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.