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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]