This study presents the microwave dielectric properties calculation of (1-x)Ba_(3.75)Nd_(9.5)Cr_(0.25)Nb_(0.25)Ti_(17.5)O_(54)–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 BaNd_2Ti_4O_(12) phase in Region I (0≤x<0.76), and both BaNd_2Ti_4O_(12) and NdAlO_3 coexist in Region II (0.76≤x<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 (εr) 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 NdAlO_3 in Region II. The measured Q×f, where f is the resonant frequency, is also consistent with the calculated value in both regions. The temperature coefficient at the resonant frequency is −1.4 ppm/°C, which agrees well with the calculated value of 0 ppm/°C. In addition, we observed a close correlation between the bulk density and the phase evolution
