New temperature stable and low loss materials of (Nd0.97Mn0.045)1.02Nb0.988O4 ceramics by La3+ substitution

• The τf value of ((Nd0.97Mn0.045)0.95La0.05)1.02Nb0.988O4 ceramic is −1.08 ppm/°C.
• The εr values was 19.82–22.34 and Q × f values were 65,700–80,000 GHz.
• The bond energy was calculated for the investigation of microwave properties.
• Variation of B-site ions was studied for the explanation of microwave properties.

(Nd0.97Mn0.045)1.02Nb0.988O4 ceramics based on La3+ substitution were prepared via a conventional solid–state reaction method. The effects of La3+ substitution for Nd3+ on microwave dielectric properties of the (Nd0.97Mn0.045)1.02Nb0.988O4 ceramics were investigated. The X-ray patterns showed that the specimens presented single NdNbO4 phase with the monoclinic fergusonite structure in the range of x = 0.0–0.05, with a further increase of the amount of substitution ions, LaNb7O19 phase appeared in this system. For the main phase, the increase of dielectric constant could be attributed to the increase in the Nd-site bond ionicity. The Q × f value and τƒ value were correlated to lattice energy and bond energy, respectively. Moreover, at 1250 °C, the ((Nd0.97Mn0.045)1−xLax)1.02Nb0.988O4 ceramics with x = 0.05 possessed excellent microwave dielectric properties: εr = 21.93, Q × ƒ = 66 700 GHz and τƒ = −1.08 ppm/°C.