The microwave dielectric properties and crystal structure of low temperature sintering LiNiPO4 ceramics

The LiNiPO4 ceramic for the LTCC technology was prepared via the traditional solid-state reaction route and its dielectric properties were investigated for the first time. The best dielectric properties of LiNiPO4 ceramics with a εr of 7.18, Q×f value of 27,754 GHz and τf of −67.7 ppm/°C were obtained in samples sintered at 825 °C for 2 h. Rietveld refinement was firstly employed to study the crystal structure and dielectric properties of LiNiPO4 ceramics. Unfortunately, the relatively large negative τf was unfavorable to practical applications. Therefore, we introduced TiO2, which possessed a considerable positive τf, to obtain a desired τf value. The prepared LiNiPO4 ceramics with 15 wt% TiO2 sintered at 900 °C for 2 h exhibited excellent dielectric properties of εr∼11.49, Q×f∼10,792 GHz, τf∼−2.8 ppm/°C. The Ag co-fired experiments confirmed the excellent chemical compatibility with LiNiPO4-TiO2 ceramics which might be potential dielectric LTCCs for high frequency applications.