Citrate precursor synthesis of perovskite-type NdAlO 3 as a microwave dielectric material
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Citrate precursor synthesis of perovskite‑type NdAlO3 as a microwave dielectric material Jiamao Li1,2 · Minghu Wei1 · Lin Li1 · Shengdao Tang3 Received: 29 June 2020 / Accepted: 24 July 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract In this work, perovskite-type N dAlO3 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 N dAlO3 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 εr = 23.44, quality factor Q × f = 67,820 GHz, and temperature coefficient of resonant frequency τf = –33.6 ppm/°C.
1 Introduction Rare-earth aluminates, R EAlO3 (RE = lanthanide elements), are one of the most important representatives among ABO3 perovskite-type oxides [1–3]. These materials exhibit a variety of unique interesting and intriguing properties such as high melting point, low Neel temperature, and good resistance to chemical attacks as well as good dielectric properties. The unit cell of NdAlO3 consists of six formula units with Nd3+ ions surrounded by twelve oxygen polyhedra and Al3+ ions surrounded by six O2− ions in octahedral coordi-− nation, resulting in a rhombohedral structure with an R 3 c space group [4]. As a typical representative of REAlO3 * Shengdao Tang [email protected] 1
School of Materials Science and Engineering, Anhui University of Technology, Maanshan 243032, People’s Republic of China
2
Key Laboratory of Green Fabrication and Surface Technology of Advanced Metal Materials, Ministry of Education, Anhui University of Technology, Maanshan 243002, People’s Republic of China
3
School of Mathematics and Physics, Anhui University of Technology, Maanshan 243002, People’s Republic of China
family, NdAlO3 has attracted much attention in last two decades as microwave components of modern communication applications in the form of resonators and filters due to its good combination of high dielectric constant and high quality factor [5]. Its inherent shortcoming of large and negative temperature coefficient of resonant frequency (τf) is also effectively made up to zero by mixing NdAlO3 with another compound with positive τf such as C aTiO3
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