Microwave Dielectric Properties of SrRE₄Si₃O₁₃ (RE=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er, Tm, Yb, and Y) Ceramics

Abstract

The apatite type SrRE4Si3O13 (RE=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er, Tm, Yb, and Y) ceramics have been prepared by the conventional solid‐state ceramic route. The phase purity and surface morphology of the sintered ceramics were studied using X‐ray diffraction and scanning electron microscopy methods. These materials showed poor sinterability and was improved by the addition of a small weight percentage of zinc borosilicate glass. The microwave dielectric properties of these materials were studied for the first time. SrRE4Si3O13 ceramics have a low relative permittivity (ɛr) in the range 9–16, a Q‐factor (Qu×f) upto 26 000 GHz and a low temperature coefficient of resonant frequency (τf). The SrLa4Si3O13 ceramics possessed a high Qu×f of nearly 26 000 GHz but with a high negative τf of −46 ppm/°C. The τf of SrLa4Si3O13 ceramics was tuned by the addition of suitable amount of TiO2.

Crystal Structure and Microwave Dielectric Properties of LiRE9(SiO4)6O2 Ceramics (RE = La,Pr,Nd,Sm,Eu,Gd, and Er)

“…The quality factor of LiLa 9 (SiO 4 ) 6 O 2 + 1 wt% LiF ceramics was 7300 GHz and that of LiSm 9 (SiO 4 ) 6 O 2 + 1 wt% LiF ceramics was 8500 GHz. In the present investigation, the τ f values of most of the compositions are relatively low compared with other silicate‐based ceramics reported so far . LiSm 9 (SiO 4 ) 6 O 2 + 1 wt% LiF sintered at 1250°C for 4 h has a nearly zero τ f of +2 ppm/°C and LiPr 9 (SiO 4 ) 6 O 2 + 1 wt% LiF has a high positive τ f of +33 ppm/°C.…”

“…The densification plays an important role in achieving excellent microwave dielectric properties of ceramics . It can be seen from the literature that several silicates, especially materials with apatite structures, show poor sinterability . In the present investigation, LiRE 9 (SiO 4 ) 6 O 2 ceramics also exhibited poor densification (60%).…”

“…reported the microwave dielectric properties of forsterite ceramics with a high quality factor and low relative permittivity. Several other silicates with excellent microwave dielectric properties have been recently reported in the literature; however, investigations of the microwave dielectric properties of new silicates are still continuing in search for materials with balanced properties for substrate applications. The relationship between structural parameters and microwave dielectric properties need to be explored to control their properties.…”

“…Among the various apatites investigated so far, the silicate oxy apatites are found to be thermally stable compared with other apatites due to their high melting point . Recently, some rare‐earth oxy apatites were found to be suitable for substrate applications . Thomas et al .…”

“…Recently, some rare‐earth oxy apatites were found to be suitable for substrate applications . Thomas et al . reported the microwave dielectric properties of SrRE 4 Si 3 O 13 (RE = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er, Tm, Yb, and Y) ceramics.…”