Preparation And Dielectric Properties Of CaO-Li₂O-Sm₂O₃-TiO₂ Microwave Dielectric Ceramics

The microwave dielectric ceramic is a kind of novel information function material.CaO-Li2O-Sm2O₃-TiO2 microwave dielectric certmics were prepared in order to obtain the low temperature coefficient of resonance frequency. XRD analysis,SEM observation and the measurements of dielectric properties at microwave frequency were employed in the present study. The relationship between phase and chemical constitution, microstructure, sintering condition, and microwave dielectric properties of microwave dielectric ceramics was investigated .xCaTiO₃-(1-x)(Li1/2Sm1/2)TiO₃ ceramics were prepared by means of solid state reaction in this paper. The pervoskite structure solid solution can be found in the calcining powders.The unit-cell volume minished with the increase of Li+ and Sm3+ quantity.The dielectric constant decreased with the increase of Li+ and Sm3+ quantity.The dielectric loss increased with the increase of Li+ and Sm3+ quantity.The temperature coefficient of resonance frequency was tunable with the increase of quantity of Li+ and Sm3+.The microwave dielectric properties ofεfrom 81 to 149.Qf values from 2489 to 4895GHz were obtained. The dielectric constant decreased with the rise of sintering temperatures. The Qf values have a maximum at sintering tempreture extent. For xCaTiO₃-(1-x)(Li1/2Sm1/2)TiO₃ ceramics the best dielectric properties were obtained with the x=0.26:ε=101,Qf=3399GHz,Ï„?=8ppm/℃.0.3CaTiO₃-0.7[Li0.5(Sm1-xNdx)0.5]TiO₃ ceramics were synthesized by the precursor method. The dielectric constant and dielectric loss increased with the increase of quantity of Nd3+. The temperature coefficient of resonance frequency decreased with the increase of quantity of Nd3+. When x=0.4,good dielectric properties were obtained for 0.3CaTiO₃-0.7[Li0.5(Sm1-xNdx)0.5]TiO₃ ceramics thatε=118,Qf=3068GHz,Ï„?=5ppm/℃ 16CaO–9Li2O–12Sm2O₃–63TiO2 ceramics were prepered by means of solid state reaction.The Sm2Ti2O7 (pyrochlore structure) was found in the calcining powders.The compactness was improved with the increase of calcining tempreture. The pervoskite structure can be found as the main crystalline phase in the sintering ceramics.The quantity of impurity phase TiO2 decreased with the rise of the calcining tempreture. Calcined at 1150℃,the phase constitution tend to be single pervoskite structure. Calcined at 1150℃,and sintered at 1340℃, the dielectric properties were obtained as following:ε=112,Qf=2535GHz,Ï„?=52ppm/℃.