Phase transition and microwave dielectric properties of Al2-xScxMo3O12 solid solutions

Al2-xScxMo3O12 (x = 0 − 0.6) ceramics were utilised using a convenient solid-state reaction. The doped Sc3+ took the place of Al3+ and formed a pure Al2-xScxMo3O12 phase. With the doping of Sc3+, the phase transition temperature was adjusted from 178 °C to below room temperature when x ≥ 0.4. Besides, the Q × f increased a lot. Pure monoclinic Al2Mo3O12 presented microwave dielectric properties of εr = 6.76, Q × f = 27,330 GHz and τf = −59.52 ppm/°C and changed from monoclinic phase to orthorhombic phase at 178 °C. When x = 0.4, Al1.6Sc0.4Mo3O12 presented orthorhombic phase at room temperature. Pure orthorhombic Al1.5Sc0.5Mo3O12 showed the best microwave dielectric properties of εr = 7.26, Q × f = 82,000 GHz and τf = −53.91 ppm/°C. •The Q × f value of Al2-xScxMo3O12 ceramics was increased from 27,330 to 82,000 GHz by replacing Al3+ with Sc3+.•The phase transition temperature of Al2-xScxMo3O12 ceramics was regulated below room temperature.•The relationship between microwave dielectric properties and crystal structure of Al2-xScxMo3O12 ceramics were investigated by using Rietveld refinement.