Effects of Ba Deficiency on Ion Ordering, Grain Growth, and Microwave Dielectric Properties of Ba1-xZn1/3Nb2/3O3 Ceramics

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Ba1-xZn1/3Nb2/3O3 (0\leq x\leq 0.02) ceramics were prepared by the solid-state reaction. The effects of Ba deficiency on the long-range order (LRO) of B-site ions, grain growth, and microwave dielectric properties of Ba1-xZn1/3Nb2/3O3 ceramics were investigated. Results show that Ba deficiency can effectively improve the sinterability of the ceramics and reduce the densification temperature by about 100 °C. The X-ray diffraction (XRD) and Raman spectra reveal that Ba-deficient samples exhibit a higher degree of LRO, and that the samples with x = 0.01 exhibit the highest degree of LRO. Furthermore, the degree of LRO increases with the decrease in sintering temperature in the range of 1400--1550 °C. Good microwave dielectric properties of \varepsilon_{\text{r}} = 39.8, Q \times f = 66532 GHz, and \tau_{\text{f}} = +23.9 ppm/°C are obtained for the Ba-deficient samples with x = 0.01 when sintered at 1450 °C for 4 h. After a second sintering process at 1400 °C/10 h during cooling, the Q \times f values of Ba1-xZn1/3Nb2/3O3 ceramics are improved. An optimized Q \times f value of 72650 GHz is obtained for the Ba0.99Zn1/3Nb2/3O3 (x = 0.01) ceramics after two-step sintering.
2012-04-25