| Summary: | 碩士 === 國立成功大學 === 資源工程學系碩博士班 === 97 === The effect of conventional solid state methods and different heat treatment conditions by controlling the cooling rate at 0.2 ℃/min with no soaking time and without control of cooling rate significantly of Ba(Mg1/3Nb2/3)O3 and Ba(Co1/3Nb2/3)O3 systems are investigated. Besides, in BMN system, we observe the order-disorder transition condition in crystal structure by improving the homogeneity of the grain size with different de-agglomerating methods. The samples are characterized the relationship between the ordering degree of the crystal structure and the microwave dielectric properties by the analysis of X-ray powder diffractiometer, Raman spectroscopy, transmission electron microscopy (TEM) , the calculation of the ordering degree and the domain size. This study investigates that different sintering temperature, decrease in the cooling rate and the homogeneity of the grain size induce the ordering degree of the B-site cations, the variation of the domain size and Q × f values.
In this investigation of BMN, the sample of 1600S-A obtains the best dielectric properties (Q × f = 78,000 GHz，εr = 32，τf = 23 ppm/℃ ). In BCN system, the sample of 1350S obtains the best dielectric properties (Q × f = 36,000 GHz，εr = 31，τf = -5.5 ppm/℃ ).
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