Effects of CaV2O6 on medium-εr microwave dielectric ceramics ZnNb2O6-x wt.%CaV2O6 with low sintering temperatures and high quality factors
The development of fifth-generation (5G)/sixth-generation (6G) mobile system highlights the importance of low-temperature co-fired ceramic (LTCC) technology. However, most medium- ε r ceramics with high quality factors are unsuitable for LTCC technology due to high sintering temperatures. Herein, a series of low-temperature-sintered ZnNb 2 O 6 - x wt.%CaV 2 O 6 ceramics, denoted as ZNO- x wt.%CVO( x =5,7,9,11), characterized by medium permittivity and high quality factors, were prepared by the solid-state reaction method. CaV 2 O 6 exists as a liquid phase during the sintering process. Moreover, liquid-phase sintering is confirmed to be the predominant mechanism for low-temperature densification of ceramics, with evidence from microstructure and activation energy. Ion substitution in the main crystalline phases, induced by ZnNb 2 O 6 –CaV 2 O 6 reaction during the sintering process, causes intrinsic impacts on microwave dielectric properties. Detailed structural analysis allows a comprehensive investigation into the extrinsic and intrinsic effects of CaV 2 O 6 on microwave dielectric properties, including quality factor Q × f , dielectric constant ε r , and temperature coefficient of resonant frequency τ f . Among all compositions, the ZNO-7 wt.% CVO ceramic sintered at 870°C exhibits great properties of Q × f = 57349 GHz, ε r = 21.63, τ f = −70.39 ppm/°C, as well as good chemical compatibility with silver (Ag). Given these advantages, the ZNO-7 wt.%CVO ceramic is a highly promising candidate for medium- ε r LTCC materials in 5G/6G applications.
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