Formation Process and Microwave Dielectric Properties of the R₂V₂O₇ (R=Ba, Sr, and Ca) Ceramics

Abstract

Formation process and microwave dielectric properties of the R2V2O7 (R=Ba, Sr, and Ca) ceramics were investigated. Transient RV2O6 phases, which were formed at 300°∼500°C by the reaction of RCO3 and V2O5, interacted with remnant RCO3 to form the homogeneous triclinic R2V2O7 phases at 600°–700°C. The Sr2V2O7 and Ca2V2O7 ceramics sintered at 1000° and 950°C, respectively, for 10 h showed a dense microstructure with the microwave dielectric properties of ɛr=10.4–12.1, Q×f=15 200–19 520 GHz, and τf=−30.9–34.8 ppm/°C. However, the Ba2V2O7 ceramic was well sintered at 900°C for 10 h and it showed the good microwave dielectric properties of ɛr=10.1, Q×f=51 630 GHz, and τf=−26.5 ppm/°C.

Temperature-stable and high Q composite ceramics in low-temperature sinterable BaO–V2O5 binary system

“…3. In general, both Ba 2 V 2 O 7 and Ba 3 (VO 4 ) 2 grains usually grow into pebble-like in monophasic or composite ceramics [10,17,[22][23][24]. Thus, it is hard to distinguish the two phases from the morphology.…”

“…Some compounds composed of TeO 2 , Bi 2 O 3 , MoO 3 , P 2 O 5 , LiO 2 , and V 2 O 5 have gained considerable attention in this context [11][12][13][14][15][16]. Among them, low-firing vanadate ceramics with light weight, low-cost, easily-processable characteristics such as Mg 2 V 2 O 7 [17], LiCa 3 MgV 3 O 12 [18], Ca 5 A 4 (VO 4 ) 6 (A = Zn, Mg) [11], Ca 5 Co 4 (VO 4 ) 6 [16], show potential microwave properties and In order to achieve a microwave dielectric material with a nearzero s f value, the most convenient and promising way is to combine two compounds having negative and positive s f values to form a solid solution or mixed phases. According to the mixture rule, it always becomes a trade-off problem when two compounds with opposite s f values were mixed, which means the improvement of s f value is always based on the sacrifice of Q Â f value.…”

“…Joung et al[17] first reported the microwave properties of Ba 2 V 2 O 7 (e r = 10.1, Q Â f = 51,630 GHz and s f = À26.5 ppm/°C) sintered at 900°C, possibly being a good candidate material for LTCC devices if its negative s f value can be tailored to be near zero.…”

Microwave dielectric properties of low temperature sintering Ca5Mn4(VO4)6 ceramics

“…Especially, advanced substrate materials with a low dielectric constant (e r ), a high quality factor (Q 9 f), and a near-zero temperature coefficient of resonant frequency (s f ) are receiving increased interest [1,2]. In addition, the low temperature cofired ceramic (LTCC) technology has been widely investigated due to significant benefits over other established packaging technologies for low-cost and miniaturization in the microwave devices [3,4].…”

Microwave dielectric properties of CaV2O6 ceramics with low dielectric loss

“…Recently extensive efforts were made in V 2 O 5 -based compounds to identify novel microwave dielectric ceramic systems suitable for LTCC substrate applications since they possess low or even ultra-low sintering temperature and excellent microwave dielectric properties [3][4][5][6][7]. According to CaO-V 2 O 5 phase diagram, the melting point of CaV 2 O 6 is about 775°C [8].…”