Effect of CaTiO3 addition on microwave dielectric properties of NdNbO4 ceramics as multi-function material

Abstract As a candidate of multi-functional material, NdNbO 4 – x CaTiO 3 ( x  = 0, 0.2, 0.4, 0.6, 0.8, 1.0, 3.0 wt.%) ceramics with improved microwave dielectric properties were prepared by conventional mixed oxide route. The effects of CaTiO 3 addition on the microstructures and microwave dielectric properties of NdNbO 4 ceramics were investigated systematically. Microscopic analysis showed that CaTiO 3 solubilized into NdNbO 4 and substituted for ions. The shift of the main peaks can be demonstrated by the changing of unit cell volumes caused from the substitution of ions. With the addition of CaTiO 3 increasing, the microwave dielectric properties of NdNbO 4 ceramics were improved. The dielectric constant e r is relative to the ionic polarizabilities and relative densities. The value of quality factors Q  ×  f increases first, and then decreases. The temperature coefficient of the resonant frequency τ ƒ has a trend of shifting toward zero in the whole range. The variation of Q  ×  f and τ ƒ could be related to the presence of grain boundaries area, porosity and the second phases. A optical Q  ×  f of 70,000 GHz, was achieved for NdNbO 4 ceramic doped with 0.6 wt.% CaTiO 3 sintered at 1275 °C for 4 h.