Microwave dielectric properties of BaTi₄O₉–BaSm₂Ti₄O₁₂ composite ceramics

Abstract

BaTi 4 O 9 and BaSm 2 Ti 4 O 12 possess large dielectric performances and low dielectric loss, but their temperature-dependent properties could not meet with the practical use. In this paper, a composite ceramic system BaTi 4 O 9 /BaSm 2 Ti 4 O 12 (BaTi 4 O 9 + xSm 2 O 3 , x = 20, 40, 60, 80 mol %) was prepared and their dielectric properties was presented. The composite ceramic precursor were modeled by a cool iso-static press (CIP) and calcined at 1300°C for 6 h. The measured densities of ceramic samples increased, but the relative densities decreased with the increase of x. XRD patterns showed there existed two phases of BaTi 4 O 9 and BaSm 2 Ti 4 O 12 in the composite. The dielectric constants increased from 39.7 to 60.0, while the quality factors decreased from 8300 to 1500. At x = 40%, a near-zero temperature coefficient of +2.2 ppm/°C was achieved. The presence of pores, Ti 3+ and Ti 2+ was proposed to be the cause of the deviation from calculated dielectric properties.

Microwave dielectric properties and microstructure of [(Mg_1–<i>_x</i>Zn<i>_x</i>)_0.95Co_0.05]_1.02TiO_3.02 ceramics

“…It has also been reported that the Fig. 4 Spots Atom (%) 3.02 (x = 0.4) ceramic at 1175°C. The degradation of the Q©f value can be attributed to abnormal grain growth at higher sintering temperatures, as shown in Fig.…”

“…The temperature coefficient of resonant frequency, TCF, can be defined as follows: 3 (sintering at 1450°C) and obtained ultra low loss for microwave applications. The proposed dielectric has an extremely low loss, making it a very promising material for microwave and millimeter wave applications.…”

Sintering temperature dependences of <i>x</i>[(Mg_0.6Zn_0.4)_0.95Co_0.05]₂TiO₄–(1 − <i>x</i>)Ca_0.8Sr₂TiO₃ microwave dielectric ceramics with a zero temperature coefficient of resonant frequency

“…The EDX datum and data of corresponding spots AB were showed in Fig. 3(b) With increasing temperature, the bulk density increased to a maximum value of 3.66 g/cm 3 at 1175°C, and then it decreased. The reduction of density due to the abnormal grain growth is shown in Fig.…”

“…3 and then remilled for 12 h. A fine powder with 3 wt % of a 10% solution of polyvinyl alcohol (PVA 500, Showa, Japan) used as a binder was pressed into pellets, 11 mm in diameter and 5 mm thick, under a pressure of 200 MPa. The pellets were sintered at temperatures of 1100 1225°C for 4 h in air.…”

Sintering temperature dependences of (1 &minus; <i>y</i>)(Mg_0.95Mn_0.05)₂(Ti_0.95Sn_0.05)O₄&ndash;<i>y</i>(Ca_0.6La_0.8/3)TiO₃ microwave dielectric ceramics with a zero temperature coefficient of resonant frequency

“…3 , which demonstrated an effective compensation in its¸f value. The resultant microwave dielectric properties were analyzed based upon the densification, the X-ray diffraction (XRD) patterns and the microstructures of the ceramics.…”