Microwave dielectric properties of aluminum substituted Ca_0.61Nd_0.26TiO₃ ceramics

Abstract

According the solid state reaction routine, Ca 0.61 Nd 0.26 Ti 1¹x Al 4x/3 O 3 (x = 0, 0.05, 0.1, 0.15, 0.2) ceramics were synthesized and their microwave dielectric properties were determined. The X-ray diffraction results showed a single perovskite phase (JCPDS Card No. 01-082-0229) for 0¯x¯0.1. Dielectric constant (¾ r ) decreased from 102.8 to 72.24, the Q©f value almost doubled, from 8560 to 15437 GHz, and the temperature coefficient of resonant frequency (¸f ) dropped from +247 to +155 ppm/°C. Then the Xray diffraction patterns showed the appearance of secondary phase that degraded microwave dielectric properties of the system rapidly. At last, a ceramic possessing microwave dielectric properties of ¾ r = 72.24, Q©f = 15437 GHz and¸f = +155 ppm/°C could be obtained when sintered at 1400°C for 2 h in air, x = 0.1.

A novel formula for the quality factor calculation for the multiphase microwave dielectric ceramic mixtures

“…There are so many reports on multiphase quality factor calculation and we cannot figure them out one by one. The dielectric constant in the range of 10- [4][5][6]8,9,[11][12][13].…”

“…In other words, the imaginary part of the dielectric constant of the multiphase ceramics also obey Eq. (6). Therefore, the dielectric loss of the mixture can be obtained from Eqs.…”

“…Microwave dielectric ceramics have been widely utilized in microwave applications, for example, resonators, because of their high dielectric constant (ε r ) and high quality factor (Q) [1][2][3][4][5][6]. Dielectric constant of ε r can result in the size of devices being ε r 1/2 times smaller; high quality factor (Q), which is approximately the reciprocal of the dielectric loss (tanı), represents low energy loss and precise frequency selection [1,2,4].…”

Structural, infrared reflectivity spectra and microwave dielectric properties of the Li7Ti3O9F ceramic

“…The ratio of (Ti 3+ )/(Ti)total was estimated to be approximately 2% based on the method proposed by Borchert et al [37]. It is well known that valence variation in titanium is ubiquitous, especially in oxides being sintered at elevated temperatures, and it is believed to be related to the released electrons due to the emergence of an oxygen vacancy [38][39][40]. The chemical defect equation can be expressed as follows:…”

Different Additives Doped Ca–Nd–Ti Microwave Dielectric Ceramics with Distorted Oxygen Octahedrons and High Q × f Value

“…The Ca 0.61 Nd 0.26 TiO 3 (CNT) ceramic with properties of ε r ∼ 108, Q × f ∼ 17 200 GHz, and τ f ∼ +270 ppm/°C, originating from CaTiO 3 ceramic is thought to be potential and suitable MWDCs applied in the high-frequency circuit . For the needs of practical application, many literatures concentrated on tuning the τ f value of the CNT ceramic to near zero by substitution of A or B site in perovskite structure , or combining other ceramics with opposite τ f value. − Nevertheless, little attention has been attached to the improvement on Q × f values by preventing reduction of Ti 4+ to Ti 3+ . Two valence states of Ti exist in many Ti-based MWDCs sintered in an air atmosphere or under low oxygen partial pressure, such as TiO 2 , BaZn 2 Ti 4 O 11 , Ba 4.2 Sm 9.2 Ti 18 O 54 , Na 0.5 Sm 0.5 TiO 3 , and so on.…”