Study Of BaO-TiO₂-ZnO System Dielectric Ceramics And Microwave Measurement Techniques

BaO-TiO₂-ZnO (BTZ) system microwave ceramics and microwave dielectric properties measurement techniques were studied.By modification of the Ti/Ba ratio and amount of ZnO, and addition of appropriate amount of Nb2O5, SnO2, and MnCO3, the microstructure and sintering behavior of the ceramics were altered so that the sintering temperature was lowered to intermediate-temperature (1160℃) and excellent dielectric properties were obtained. Co-substitution of Zn²⁺ and Nb⁵⁺ for Ti⁴⁺ led to formation of solid solutions, which contributed to liquid-phase sintering. Sn⁴⁺'s substitution for Ti⁴⁺ helped formation of substitutive solid solutions, reduced the free energy and lowered the sintering temperature. Sn⁴⁺ and Mn2+ (by means of valance transition) both served as oxidizers which suppressed Ti⁴⁺ reduction and increased the Q factor. Besides, addition of glass further reduced the sintering temperature to as low as 960℃.By control of calcination and sintering temperatures, as well as the ball-milling time, the phases present and microstructure were adjusted so that optimal dielectric properties were obtained. The formation of transitional phases like BaTi₅O₁₁ were important for the formation of the main phases BaTi₄O₉ and Ba₂Ti₉O₂₀. Changing the sintering temperature was effective in altering the ceramics density and dielectric characteristics. Ball-milling also affected the dielectric properties by both producing fine-grained powders and changing the compositions.Two microwave ceramics in the BTZ system were obtained, with the major dielectric characteristics as follows:Waveguide and Open Resonate Cavity (ORC) methods were utilized to measure the dielectric properties of the microwave ceramics. For the waveguide method, the Least Square algorithm and iteration method were adopted to solve the thickness resonance and multi-solution problems. Analyses showed that this algorithm is effective even when dielectric constant varies much with the frequency.For the ORC method, three algorithms were given: (1) linear or cubic spline interpolation; (2) Least-Square-based experience equation; (3) Artificial Neural Network (ANN). The precision and complexity of the algorithms were analyzed. For the ANN method, the partial ANN model was selected according to the specific problem, significantly simplifying the calculation and improving the speed. The methods mentioned in the paper are considered important for microwave material measurement and related investigations.