Low sintering BaNd2Ti4O12 microwave ceramics prepared by CuO thin layer coated powder

Recently, BaO–Nd2O3–TiO2 systems are widely studied for microwave applications because of their high dielectric constant and high quality factor. However, pure BaNd2Ti4O12 ceramics without additives have to be sintered above 1300 °C to achieve densification. Copper oxide has been known as a good sintering aid for electronic ceramics and less reactive toward silver. We have introduced the CuO into BaNd2Ti4O12 by modifying the surface of BaNd2Ti4O12 by CuO thin layer on the calcined powder instead of mixing CuO directly with BaNd2Ti4O12 powder. The process reduces the amount of sintering aid and minimized the negative impact of sintering aid on dielectric properties such as quality factor. The CuO precursor solution of Cu(CH3COO)2, Cu(NO3)2 and CuSO4, were used to prepare CuO thin layer. They were investigated individually to determine their effects on the densification, crystalline structure, microstructure and microwave dielectric properties of BaNd2Ti4O12. The CuSO4 coated BaNd2Ti4O12 sintered at 1150 °C has exhibited better dielectric properties than those of CuO doped BaNd2Ti4O12 (k, 62.5 versus 61.2; Q × f, 11,500 GHz versus 10,500 GHz). The thin layer dopant coating process has been found to be a very effective way to lower ceramic sintering temperature without scarifying its dielectric properties.