The crystal structure and microwave (MW) dielectric properties of AHfO(3) (A = Ba, Sr, and Ca) ceramics prepared by the solid-state route have been investigated. X-ray and electron diffraction show BaHfO3 to be an untilted cubic perovskite (a(0) a(0) a(0), space group Pm (3) over barm), whereas SrHfO3 and CaHfO3 are both orthorhombically distorted perovskites (a(-) b(+) a(-), space group Pnma). AHfO(3) ceramics with a relative density similar to 90% of the theoretical X-ray density and microstructures consisting of randomly oriented equiaxed grains were prepared by. ring at 1750 degrees C for 6 h. Conventional transmission electron microscopy reveals the occurrence of long parallel ferroelastic domains in the subgrain microstructure of CaHfO3 and SrHfO3. At room temperature and MW frequencies, AHfO(3) ceramics, where A = Ba, Sr, and Ca, have epsilon(r) similar to 24.2, Q x f(r) similar to 14250 GHz (at 8.9 GHz) and tau(f)similar to+111 ppm/K; epsilon(r)similar to 23.5, Q x f(r)similar to 33534 GHz (at 9.3 GHz), and tau(f)similar to-63 ppm/K; and epsilon(r)similar to 21.4, Q x f(r)similar to 15950 GHz (at 8.9 GHz), and tau(f)similar to-33 ppm/K, respectively. The ion polarizability for Hf4+ in a cubic perovskite environment is calculated to be 3.32 angstrom(3), whereas in a noncubic environment it increases to 4.36-4.47 angstrom(3). Finally, the dielectric properties of AHfO(3) (A = Ba, Sr, and Ca) are compared with their titanate and zirconate counterparts.