Processing and Characterization of Microwave Dielectric Ceramics and Thin Films-Nd2(Ti2/3Al1/3)3O9-δ and (Ba0.7Sr0.3)TiO3

Reactive powders of stoichiometry Nd2(Ti2/3Al1/3)3O9-δ and thin films of (Ba0.7Sr0.3)TiO3 have been prepared by the conventional mixed-oxide method and the metal-organic deposition method, respectively. The corresponded phases after calcination and sintering are investigated by XRD diffraction. Single phase of Nd2(Ti2/3Al1/3)3O9-δ could be only obtained by sintering over 1400C for 4 h. (Ba0.7Sr0.3)TiO3 thin film well crystallizes at as low as 570C after Au-doping by MOD method. Nd2(Ti2/3Al1/3)3O9-δ posses excellent temperature stability of frequency. Substitution of Nd by Ca, Sr, or Pb can also readily form the single phase (Nd,X)2Ti3O9-δ, but inferior microwave properties are observed. The leakage current of BST thin films are found to be reduced by doping Au or codoping Mg/La or Mg/Nb. Mg/La and Mg/Nb reduces leakage current even more when annealing is performed at high temperatures.