Citrate precursor synthesis of perovskite-type NdAlO 3 as a microwave dielectric material

In this work, perovskite-type NdAlO3 dielectric material was synthesized via the simple and effective polymeric precursor method using citric acid as complex agent. The prepared NdAlO3 was systematically characterized by thermogravimetric–differential scanning calorimetry (TG–DSC), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) to investigate its structural characteristics. The sintering behavior and microwave dielectric properties of NdAlO3 ceramics derived from the as-synthesized powders were discussed. The XRD results indicated that pure phase NdAlO3 powders were obtained at 800 °C, lowering about 400 °C than that prepared by the solid-state reaction route. The TEM micrograph revealed that slight agglomeration was formed for the NdAlO3 powders with an average particle size of 33.5 nm. After being sintered at 1500 °C for 4 h, the NdAlO3 ceramics exhibited a high relative density of 98.8% and favorable microwave dielectric properties: dielectric constant er = 23.44, quality factor Q × f = 67,820 GHz, and temperature coefficient of resonant frequency τf = –33.6 ppm/°C.