La3 +/Sm3+ co-doped (LaxNd1–2xSmx)2MoO6 ceramics: Achieving a near-zero temperature coefficient of resonant frequency

A molybdate system by a low sintering temperature and excellent dielectric properties was selected. • The coupling mechanism of microwave dielectric properties regulated by doping gradient and sintering temperature is clarified. • We obtained materials with proper ε r , Q×f and near-zero τ f of resonance frequency. Molybdate-based ceramics have attracted considerable interest for microwave device applications owing to their intrinsically low sintering temperatures and compositionally tunable dielectric responses. The rapid advancement of emerging technologies — including 5 G/6 G communications, satellite Internet of Things, radar systems, intelligent vehicles, and wearable electronics — has imposed increasingly stringent demands on the performance of microwave dielectric ceramics. In this work, (La x Nd 1–2x Sm x ) 2 MoO 6 ceramics with La 3+ and Sm 3+ co-occupying the A‑site were synthesised via a conventional solid‑state reaction route. The effects of sintering temperature and doping concentration on the phase constitution, microstructure, and microwave dielectric properties were systematically investigated. The underlying mechanisms governing their evolution were elucidated through relative-density and chemical-bonding analyses. The microwave dielectric properties of the (La x Nd 1–2x Sm x ) 2 MoO 6 ceramics are summarised as follows: at T = 1000 °C, ε r = 7.91–13.56, Q×f = 10,280–27,940 GHz, and τ f = -15.69 to −6.20 ppm/°C; at T = 1100 °C, ε r = 6.91–7.64, Q×f = 3890–7120 GHz, and τ f = -15.84 to −10.53 ppm/°C; and at T = 1200 °C, ε r = 13.64–15.24, Q×f = 7240–8910 GHz, and τ f = -24.46 to −9.21 ppm/°C. Furthermore, at a sintering temperature of 950 °C, the ceramics exhibit favourable chemical compatibility with silver, satisfying the key requirements of low-temperature co-fired ceramic (LTCC) technology for both densification temperature and electrode co-firing stability. Download: Download high-res image (142KB) Download: Download full-size image