Microwave Dielectric Properties of New Complex Perovskites: (Ba_1/3Ln_2/3)(Zn_1/3Ti_2/3)O₃ (Ln=La, Pr, and Nd) and (Ba_(1+x)/3La_(2-x)/3)(Zn_1/3Ti_(2-x)/3Nb_x/3)O₃

Abstract

Complex perovskites of the formula (Ba1/3Ln2/3)(Zn1/3Ti2/3)O3 (Ln=La, Pr, and Nd) and (Ba(1+x)/3La(2-x)/3)(Zn1/3Ti(2-x)/3Nbx/3)O3 (x=0.5,0.75,1.0,1.25) have been synthesized by solid state reactions and are found to crystallize in the cubic structure (space group Pm3m) from Rietveld refinement of powder X-ray data. The lattice parameter and the grain size increases with Nb substitution. Among the above oxides, (Ba1/3La2/3)(Zn1/3Ti2/3)O3 shows the best dielectric properties with quality factor (Q) of 3139 at 6.67 GHz and a temperature coefficient of resonant frequency (τf) of -10.8 ppm/°C. Further, the temperature coefficient of resonant frequency (τf) shows a large and systematic variation (with a continued decrease and a change of sign from positive to negative) with increase in Nb content.