Calcium stannate dielectrics compacted by spark plasma sintering

• Published in: Materials science & engineering. B, Solid-state materials for advanced technology Vol. 317; no. C; p. 118203
• Main Authors: Ctibor, Pavel, Sedláček, Josef, Straka, Libor, Veselý, Petr, Lukáč, František
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.07.2025; Elsevier
• Subjects: Calcium stannate; Microstructure; Permittivity; Spark plasma sintering; Temperature-compensated dielectrics; Calcium stannate; Spark plasma sintering; Microstructure; Permittivity; Temperature-compensated dielectrics
• ISSN: 0921-5107
• DOI: 10.1016/j.mseb.2025.118203

•CaSnO3 powder sintered via Spark plasma sintering to make high-quality dielectrics.•The resulting compacts offer an inorganic material with promising electrical behavior: εr = 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, CaSnO3, 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, εr = 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.