Huanfu Zhou

Effect of Zn2+ Substitution on Sintering Behavior and Dielectric Properties of NdNbO4 Ceramics

The effects of Zn2+ substitution on the sintering behavior and dielectric properties of Nd1−xZnxNbO4−x/2 ceramics were investigated. The synthetic process and phase evolution were studied using TG-DSC and X-ray diffraction (XRD) analysis. The results show that Zn2+ substitution lowers the densification temperature of NdNbO4 ceramics. A single phase of monoclinic NdNbO4 was obtained by appropriate substitution (x = 0.05) of Zn2+ for Nd3+ in NdNbO4 ceramics. As the Zn2+ content increased to x = 0.1, ZnNb2O6 phase appeared in the ceramic. The dielectric constant ϵr increased slightly from 17 to 19 with the content of Zn2+ increasing from 0 to 0.2 mol. The quality factor Q×f firstly increased and then decreased and reached the highest values of Q×f = 60,000 GHz at x = 0.1. The temperature coefficient of resonant frequency τf shifted from −37 ppm/°C to −45 ppm/°C with the Zn2+ content increasing.

Effect of B2O3 Additions on the Sintering Temperature and Microwave Dielectric Properties of 5.5Li2O-Nb2O5 −7TiO2 Ceramics

The effects of B 2 O 3 addition on the sintering behavior, microstructure, and the microwave dielectric properties of 5.5Li 2 O-Nb 2 O 5− 7TiO 2 (LNT) ceramics have been investigated. The low-amount addition of B 2 O 3 can effectively lower the sintering temperature of LNT ceramics from 1075 to 875°C and induce no obvious degradation of the microwave dielectric properties. Typically, the 1.0 wt.% B 2 O 3 added ceramic sintered at 875°C has better microwave dielectric properties of ϵ r = 40.8, Q × f = 15, 560 GHz, τ f = 50 ppm/°C. Obviously, the LNT ceramics can be applied to microwave LTCC devices.

Microwaves Dielectric Properties of 3Li2O-Nb2O5-6TiO2 Ceramics with B2O3 Addition

The effects of B2O3 addition of on sintering behavior, microstructure, and microwave dielectric properties of a new Li2O-Nb2O5-TiO2 (LNT) ceramics: 3Li2O-Nb2O5–6TiO2 has been investigated. The compound is composed of two phases, TiO2 and ‘‘M-phase’’ solid solution phase. The low-amount doping of B2O3 can effectively lower the sintering temperature from 1125°C to 900°C without inducing obvious degradation of microwave dielectric properties. The 1 wt.% B2O3-doped ceramic sintered at 900°C has better microwave dielectric properties of ϵr = 52, Q × f = 12000 GHz, τf = 32.3 ppm/°C. Moreover, there is no reaction occurred when co-firing the LNT ceramic with Ag electrode, which suggests that the ceramics can be applied to microwave LTCC devices.

Microwave Dielectric Properties of Low Temperature Firing BaxCu2−xP2O7 Ceramics

A new kind of microwave dielectric ceramics of BaxCu2−xP2O7 with low sintering temperature was prepared by solid state reaction method. The densified temperatures of the sintered samples are range from 850°C to 900 °C. The best microwave dielectric properties can be obtained in Ba1.5Cu0.5P2O7 ceramic sintered at 875°C for 2hrs with permittivity of 7.1, Q×f value of 31,000GHz and TCF value of −51 ppm/°C. The microwave dielectric properties and low sintering temperatures of BaxCu2−xP2O7 ceramics make them a promising candidate for LTCC applications.