Correlation between crystal structure and microwave dielectric properties of CaRE 4 Si 3 O 13 (RE = La, Nd, Sm, and Er)

Novel CaRE4Si3O13 (RE = La, Nd, Sm, and Er) microwave dielectric ceramics were prepared using solid-state reaction sintered at 1350–1400 °C for 5 h. CaRE4Si3O13 (RE = La, Nd, Sm, and Er) possessed an apatite structure with the P63/m space group. The lattice parameters a, b and c; theoretical density and unit cell volumes of CaRE4Si3O13 (RE = La, Nd, Sm, and Er) gradually decreased when RE changed from La to Er, and a pure phase was formed at all compositions. The er, Q × f, and τf values of the CaRE4Si3O13 (RE = La, Nd, Sm, and Er) ceramics were related to the total ionic polarizability, packing fraction, and polyhedral distortion of RE/Ca(2)O7, respectively. The optimal microwave dielectric properties of the CaRE4Si3O13 ceramics (er = 13.37, Q × f = 18,600 GHz, and τf =  − 17.8 ppm/°C) were obtained at RE = Er.