| In order to search new high-s dielectric materials, the structure and dielectric properties of (l-x)(Ca0.61Nd0.26)TiO3/x(Li1/2Nd1/2)TiO3 microwave dielectric ceramics were investigated together with the dielectric ceramics BapLne-pTig-pM2+pO30 (Ln=La, Nd, Sm; M=Ta, Nb) with filled tungsten bronze structure. The relaxation nature of the filled tungsten bronze BapLn6.pTig.pM2+pC>3o (Ln=La, Nd, Sm; M=Ta, Nb) was extensively investigated. At the same time, the possibility of microwave applications was discussed for filled tungsten bronze ceramics.Microwave dielectric ceramics of(l-x)(Ca0.61Nd0.26)TiO3/x(Lii/2Ndi/2)TiO3 (y = 0.39, 0.4 <= x < 0.6) were prepared at a relatively low sintering temperature (T < 1250癈), and microwave dielectric properties and crystal structure were investigated with respect to the (Lii/aNdi/2)TiO3 content. A complete solid solution with orthorhombic CaTiOs-type perovskite structure formed within the entire composition range of the investigation. The permittivity increased till to x = 0.5, and then decreased. Qf value and temperature coefficient of resonant frequency decreased gradually as (Lii/2Ndi/2)TiO3 content increased. Good microwave dielectric properties were obtained for (l-x)(Cao.6iNdo.26)TiO3/x(Lii/2Ndi/2)TiO3 ceramics with x = 0.6 (e = 122.5, Qf = 1,652 GHz, tf = 5.2 ppm/) and x = 0 (e = 107.7, Qf= 11,455 GHz, Tf = 236.7 ppm/). hi addition, the relationship between microwave dielectric properties and crystal structure was investigated in terms of the bond valence of the cations at A sites. Qf value and temperature coefficient of resonant frequency decreased when the average bond valence of the cations at A sites decreased.The high dielectric constant and low loss BapNd6-pTi8.pTa2+pO30 (p = 4, 5) ceramics with filled tungsten bronze structure were modified through substitution at A, B or A/B sites and introducing secondary phase. Through these modifications, some dielectric ceramics were obtained suitable for the temperature compensated capacitor. For example, the dielectric properties were s = 114, tan8 =0.0005, TE = -664ppm/ for the dielectric ceramics of Ba4Nd2Ti4+xTa |
PDF Full Text Request