Calcium stannate dielectrics compacted by spark plasma sintering

• CaSnO 3 powder sintered via Spark plasma sintering to make high-quality dielectrics. • The resulting compacts offer an inorganic material with promising electrical behavior: ε r = 28.2; tan(δ) = 0.036 and TCC = 26 ppm/K at 1 MHz. • The system contained oxygen vacancies and certain degree of valency change on Sn. The positively charged O-vacancies and negatively charged Sn ions partly compensated their role in a high-frequency polarization and therefore the low thermal coefficient of capacitance (TCC) was achieved. The aim of this work was to sinter calcium stannate dielectric ceramics, CaSnO 3 , via spark plasma sintering (SPS). The material is difficult to sinter, mainly because of Sn volatility. A semi-commercial powder product was consolidated into a form of bulk discs by SPS. As the main variable parameter, the hot-compaction pressure varied from 30 MPa to 80 MPa. The as-sintered bulks were studied by microscopy, phase analysis, X-ray photoelectron spectroscopy and microhardness. The samples were covered with electrodes and dielectric parameters were measured, including DC resistance. Relative permittivity and loss tangent values for the frequency range 1 kHz to 1 MHz and the temperature range 30 °C to 200 °C were very stable with no relaxation. Connections between the sintering parameters, microstructure and dielectric characteristics were found. Samples sintered at the pressure over 30 MPa behaved like reliable dielectrics. A novel approach to sintering of very promising dielectrics was developed: The sample sintered at 1300 °C using 50 MPa pressure exhibited very interesting values, ε r = 28.2; tan(δ) = 0.036 and thermal coefficient of capacitance TCC = 26 ppm/K at 1 MHz. The influence of vacancies and ion valence modifications was discussed.