Effect of Zn2+ substitution on the microwave dielectric properties of LiMgPO4 and the development of a new temperature stable glass free LTCC

The LiMg(1−x)ZnxPO4 ceramics have been prepared by the solid state ceramic route. The LiMg(1−x)ZnxPO4 ceramic retains the orthorhombic structure up to x = 0.2. The compositions with 0.3 ≤ x ≤ 0.8 exist as a mixture of orthorhombic and monoclinic phases. When Mg2+ is fully replaced with Zn2+ (x = 1.0) complete transition to monoclinic phase occurs. The ceramic with x = 0.1 (LiMg0.9Zn0.1PO4) sintered at 925 °C exhibits low relative permittivity (ɛr) of 6.7, high quality factor (Qu × f) of 99,700 GHz with a temperature coefficient of resonant frequency (τf) of −62 ppm/°C. The slightly large τf is adjusted nearly to zero with the addition of TiO2. LiMg0.9Zn0.1PO4–TiO2 composite with 0.12 volume fraction TiO2 sintered at 950 °C shows good microwave dielectric properties: ɛr = 10.1, Qu × f = 52,900 GHz and τf = −5 ppm/°C. The ceramic is found to be chemically compatible with silver.