Synthesis Ba0.6Sr0.4TiO3–ZnNb2O6 composite ceramics using chemical coating method

A coating approach for preparing 0.8Ba0.6Sr0.4TiO3–0.2ZnNb2O6 (hereafter BSTZ) composite ceramics was investigated. The Al2O3-coated Ba0.6Sr0.4TiO3 particles were prepared successfully by chemical coating method and used as raw materials to fabricate BSTZ composite ceramics. After BSTZ ceramic sintered at 1280 °C, the BaNb3.6O10 phase was suppressed, which should attributed to the separation of Ba0.6Sr0.4TiO3 and ZnNb2O6 by the Al2O3 coating. The sintered BSTZ ceramics exhibited excellent dielectric temperature stability, with a moderate dielectric constant (ɛr = 640.8) and a low dielectric loss (tan δ = 0.0078) at 10 kHz. The dielectric constant change with temperature for BSTZ ceramics was less than ±5% over the temperature range of −55 °C to 125 °C, meeting the requirement of the X7R type capacitor specification. The tunability of the sample is 7.2% under a dc electric field of 3 kV/mm, which made it a promising candidate material used for the tunable ceramic capacitors and the phase shifters.