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.