Microstructure and microwave dielectric properties of low-temperature sinterable (1 − x)Ba3(VO4)2–xCaWO4 composite ceramics

Abstract

Low-temperature-sintered Ba 3 (VO 4 ) 2 -CaWO 4 composite ceramics were prepared by cofiring mixtures of pure-phase Ba 3 (VO 4 ) 2 and CaWO 4 . The thermo-mechanical analysis revealed that the CaWO 4 in the composite ceramic can significantly promote the densification process and lower the sintering temperature to *900°C. The X-ray diffraction results indicated that Ba 3 (VO 4 ) 2 and CaWO 4 phases coexist in the sintered ceramics, and no secondary phases can be detected in the composite, implying the good chemical compatibility between the two phases. The near-zero temperature coefficients of the resonant frequency (s f ) could be achieved by adjusting the relative content of the two phases owing to their opposite s f values. The composite ceramics with 60 wt% CaWO 4 sintered at 900°C exhibited desirable microwave dielectric properties of the quality factor Q 9 f * 37,000 GHz, dielectric constant e r * 12, and s f * -1.4 ppm/°C.

Sintering behavior, structural phase transition, and microwave dielectric properties of La1‐xZnxTiNbO6‐x/2 ceramics

“…The basic reason might be ascribed to the fact that both a slight lattice distortion from the occupancy of smaller Zn 2+ ions at La 3+ sites and a tiny amount of oxygen vacancies for charge balance would accelerate the mass mobility and promote the densification of the matrix ceramics. 18 The densification of the LTN+0.005ZnO composition was not significantly improved probably because of the insufficient amount of ZnO sintering aid for possible liquid phase sintering in this work. Figure 3 shows XRD patterns of all studied compositions sintered at different temperatures.…”

“…In addition, among these samples, the shrinkage rate of the LZTN‐0.005 ceramic was the biggest and also the maximum densification shrinkage was observed at 1350°C. The basic reason might be ascribed to the fact that both a slight lattice distortion from the occupancy of smaller Zn 2+ ions at La 3+ sites and a tiny amount of oxygen vacancies for charge balance would accelerate the mass mobility and promote the densification of the matrix ceramics . The densification of the LTN+0.005ZnO composition was not significantly improved probably because of the insufficient amount of ZnO sintering aid for possible liquid phase sintering in this work.…”

Low‐Temperature Sinterable (1−x)Ba3(VO4)2–xLiMg0.9Zn0.1PO4 Microwave Dielectric Ceramics

“…Ba 3 (VO 4 ) 2 ceramic was reported to have a large positive τ f value (52 ppm/°C) and good microwave dielectric properties (ε r ~14, Q × f ~ 42 000 GHz) as it was sintered at ~1100°C. Compared with other microwave dielectric materials with positive τ f values such as TiO 2 , CaTiO 3 , and SrTiO 3 , relatively good microwave dielectric properties make Ba 3 (VO 4 ) 2 be usually used as a τ f ‐tailoring material, such as Ba 3 (VO 4 ) 2 –BaWO 4 and Ba 3 (VO 4 ) 2 –CaWO 4 systems . Moreover, its relatively low sintering temperature allows Ba 3 (VO 4 ) 2 ‐based microwave dielectric ceramic systems to be easily sintered.…”

Preparation and microwave dielectric properties of Li 3 (Mg 0.92 Zn 0.08 ) 2 NbO 6 –Ba 3 (VO 4 ) 2 composite ceramics for LTCC applications

“…It has been employed as a positive τ f -tailoring material in many composite ceramics, for instance BV-LiMg 0.9 Zn 0.1 PO 4 , BV-CaWO 4 , BV-Zn 2-x SiO 4-x , BV-MgSiO 4 [13][14][15][16], in which the sintering temperature could be lowered obviously in addition to acceptable microwave dielectric properties. In these composite ceramics, the two components often form diphasic composites instead of solid solutions because of their different crystal structures.…”