Microwave dielectric properties of (1-x)Ba3.75Nd9.5Cr0.25Nb0.25Ti17.5O54-xNdAlO3 ceramics

This study presents the microwave dielectric properties calculation of (1-x)Ba3.75Nd9.5Cr0.25Nb0.25Ti17.5O54-xNdAlO(3) ceramics where x denotes the volume molar fraction. From X-ray diffraction results, the solid solution limit is calculated to be about 0.76, where it forms a single BaNd2Ti4O12 phase in Region I (0x<0.76), and both BaNd2Ti4O12 and NdAlO3 coexist in Region II (0.76x<1). The solid solution limit is confirmed by independently calculating it from the dielectric constant data. There is less than 4% deviation between the measured dielectric constant (epsilon(r)) and the one calculated from the Maxwell-Wagner formula. The total quality factor (Q) remains almost constant in Region I and increases rapidly with the volume molar fraction of NdAlO3 in Region II. The measured Qxf, where f is the resonant frequency, is also consistent with the calculated value in both regions. The temperature coefficient at the resonant frequency is -1.4ppm/degrees C, which agrees well with the calculated value of 0 ppm/degrees C. In addition, we observed a close correlation between the bulk density and the phase evolution.