0.73ZrTi2O6-0.27MgNb2O6 microwave dielectric ceramics modified by Al2O3 addition

0.73ZrTi(2)O(6)-0.27MgNb(2)O(6) ceramics with various Al2O3 contents (0-2.0wt%) were prepared by conventional ceramic route. The effects of Al2O3 on the phase composition, microstructure, conductivity, and microwave dielectric properties were systematically investigated. The coexistence of a disordered -PbO2-type phase and a rutile second phase was found in all compact ceramics with low Al2O3 contents (x=0, 0.5, and 1.0wt%), while a corundum phase was detected when Al2O3 additive increased to 1.5 and 2.0wt% based on X-ray diffraction results. With the addition of Al2O3, the decreased grain size of the matrix phase was observed using field-emission scanning electron microscope, accompanied with increased resistivity and band-gap energy. Additionally, Al2O3 additives efficiently improved the quality factor of the ceramics. After sintering at 1360 degrees C for 3hours, the ceramic with 1.0wt% Al2O3 exhibited excellent microwave dielectric properties: a dielectric constant of 43.8, a quality factor of 33900GHz (at 6.6GHz), and a near-zero temperature coefficient of resonant frequency (3.1ppm/C-degrees).