Wide permittivity stability against temperature of high-permittivity and low-loss (Sr6-xCax)Ti2Nb8O30 tungsten bronze ceramics

A series of (Sr6-xCax)Ti2Nb8O30 (x = 0, 0.1, 0.3, 0.5, 1.0, 2.0) solid solutions were synthesized using a conventional solid-state method, and the effects of different Ca2 + doping amounts on the crystal structure and dielectric properties of the (Sr6-xCax)Ti2Nb8O30 ceramics were systematically studied. The results showed that the ceramics exhibited a tetragonal phase under all x values, and the lattice constant of the (Sr6-xCax)Ti2Nb8O30 ceramics decreased gradually as x increased. When x = 0, the relaxation dielectric peak appeared near - 75 degrees C in the ceramic samples, accompanied by a frequency-dispersion characteristic of relaxation ferroelectrics. In contrast, for other x values, the dielectric peak appeared near 150 degrees C and took on a rightward shift trend as x increased. At x = 1.0, the peak broadened, whereas at x = 2.0, a division peak appeared. This division may have resulted from the transition between paraelectric-ferroelectric and ferroelectric-ferroelastic states. In addition, the (Sr6-xCax)Ti2Nb8O30 ceramics exhibited a high relative permittivity (epsilon r approximate to 700) and low loss (tan delta approximate to 0.05) at x = 0.3, and the relative permittivity had a wide range of temperature stability from - 100 degrees C to 50 degrees C. The findings provide new research directions for the design and application of materials in chip ceramic capacitors.