Low loss, temperature stable dielectric ceramics in ZnNb2O6-Zn3Nb2O8 system for LTCC applications

Abstract

(1 - x)ZnNb2O6-xZn(3)Nb(2)O(8) mixed phase ceramics have been prepared by conventional solid state ceramic route by both mixing ZnO with Nb2O5 and by ZnNb2O6 with Zn3Nb2O8, respectively. The sintered ceramics have high relative permittivity (epsilon (r) = 23-25), high quality factor (Q (u) xf) up to 95,500 GHz and temperature coefficient of resonant frequency (tau (f) ) in the range -55 to -73 ppm/A degrees C. The quality factors are higher for the mixtures when prepared from ZnNb2O6 and Zn3Nb2O8. The 0.5ZnNb(2)O(6)-0.5Zn(3)Nb(2)O(8) has Q (u) xf = 95,500 GHz (at 5.16 GHz), epsilon (r) = 22.7 and tau (f) = -65 ppm/A degrees C when sintered at 1200 A degrees C. The tau (f) of the ceramic has been tuned close to zero by the addition of ZnTa2O6, which has a positive tau (f) . The ceramic composition (1 - y)[0.5ZnNb(2)O(6)-0.5Zn(3)Nb(2)O(8)]-yZnTa(2)O(6) with y = 0.91 shows epsilon (r) = 34.7 and Q (u) xf = 41,950 GHz (at 4.63 GHz) and zero tau (f) . In order to lower the sintering temperature of 0.5ZnNb(2)O(6)-0.5Zn(3)Nb(2)O(8) ceramic for low temperature co-fired ceramic applications, low melting additives such as CuO, B2O3 and ACuB(2)O(5) (A-Ba, Sr, Zn, Ca) have been added. 12 wt% ZnCuB2O5 added 0.5ZnNb(2)O(6)-0.5Zn(3)Nb(2)O(8) ceramic sintered at 875 A degrees C has Q (u) xf = 39,750 GHz (at 5.89 GHz), epsilon (r) = 18.3 and tau (f) = -88 ppm/degrees C