Influence of Zn nonstoichiometry on the phase structure,microstructure and microwave dielectric properties of Nd(Zn0.5Ti0.5)O3ceramics
The double perovskites Nd(Zn0.5+xTi0.5)O3 (x = 0.05, 0.03, 0.01, 0, −0.01, −0.03 and −0.05) have been prepared successfully by conventional route for mixing oxides. The influences of Zn nonstoichiometry on the phase composition, microstructure and microwave dielectric properties have been systematically discussed. A small amount of Zn nonstoichiometry (−0.01 ≤ x ≤ 0.03) did not change the phase composition but a large amount of Zn excess (x = 0.05) and deficient (x = -0.03 and −0.05) caused the appearances of secondary phases Zn2TiO4 and Nd2Ti2O7, respectively. A significant difference in grain size could be observed in the Zn nonstoichiometry ceramics. The sinterability and density were reduced due to the presence of the impurity phase Nd2Ti2O7 for the Zn-deficient ceramics, while Nd2Ti2O7 could adjust temperature coefficient of resonant frequency (τf) to near-zero. The τf of the Nd(Zn0.5+xTi0.5)O3 (x = −0.05-0.05) ceramics was significantly affected by the Zn nonstoichiometry. After sintered at 1360 °C for 4 h, the nonstoichiometric Nd(Zn0.51Ti0.5)O3 ceramics showed favorable microwave dielectric properties: dielectric constant εr = 36.41, quality factor Q x f = 182650 GHz, and τf = −26.5 ppm/oC and the Nd(Zn0.47Ti0.5)O3 ceramics possessed a near-zero τf value of −5.6 ppm/oC, accompanying by a high εr and a moderate Q x f (εr = 27.75, Q x f = 47820 GHz).