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Abstract: Nd2SiO5 ceramics were synthesized and their microwave dielectric properties were investigated. The hexagonal Nd4Si3O12 second phase disappeared and the pure monoclinic Nd2SiO5 phase could be obtained when the molar ratio of Nd2O3/SiO2 was 1:1.05 at 1450°C. The relative density of Nd2SiO5 ceramics increased with increasing temperature. The Nd2SiO5 ceramics sintered at 1500°C exhibited microwave dielectric properties: a dielectric constant (ε r) of 7.94, a quality factor (Q × f) of 38 800GHz and a temperature coefficient of resonant frequency (τ f) of −53ppm/°C. High resonant frequency led to a low dielectric constant and low Q × f value. Nd2SiO5 ceramics have a wide sintering temperature region. They are promising candidate materials for microwave passive components. [Copyright &y& Elsevier]

The Sm2SiO5 ceramics were synthesized and their microwave dielectric properties were investigated. The pure monoclinic Sm2SiO5 phase could be obtained when the molar ratio of Sm2O3/SiO2 was 1:1.05 at 1350°C. A small amount of hexagonal Sm4(SiO4)3 second phase occurred as temperature increased. The relative density of Sm2SiO5 ceramics increased with increasing temperature. The Sm2SiO5 ceramics sintered at 1500°C exhibited microwave dielectric properties: a dielectric constant (εr) of 8.44, a quality factor ( Q × f) of 64 000 GHz, and a temperature coefficient of resonant frequency (τf) of −37 ppm/°C. The Sm2SiO5 ceramics have a wide sintering temperature region and small negative τf values. They are promising candidate materials for millimeter-wave devices. [ABSTRACT FROM AUTHOR]

Abstract: SnO2-doped CaSiO3 ceramics were successfully synthesized by a solid-state method. Effects of different SnO2 additions on the sintering behavior, microstructure and dielectric properties of Ca(Sn1−x Si x )O3 (x=0.5–1.0) ceramics have been investigated. SnO2 improved the densification process and expanded the sintering temperature range effectively. Moreover, Sn4+ substituting for Si4+ sites leads to the emergence of Ca3SnSi2O9 phase, which has a positive effect on the dielectric properties of CaO–SiO2–SnO2 materials, especially the Qf value. The Ca(Sn0.1Si0.9)O3 ceramics sintered at 1375°C possessed good microwave dielectric properties: ε r =7.92, Qf =58,000GHz and τ f =−42ppm/°C. The Ca(Sn0.4Si0.6)O3 ceramics sintered at 1450°C also exhibited good microwave dielectric properties of ε r=9.27, Qf=63,000GHz, and τ f =−52ppm/°C. Thus, they are promising candidate materials for millimeter-wave devices. [Copyright &y& Elsevier]