Effect of phase transition on the microwave dielectric properties of BiNbO4

BiNbO4 specimens were transformed from the orthorhombic to triclinic phase at 1040 °C. The calculated intrinsic dielectric properties of the specimens were changed from K = 42, Qf = 15700 GHz in the orthorhombic phase to K = 30, Qf = 8900 GHz in the triclinic phase. The change of Qf value resulted from the increase of the dispersion parameter and modes for nonsymmetrical structure with the phase transition. TCF of the specimens decreased due to the increase of the octahedral distortion of BiNbO4 with change from the orthorhombic to the triclinic phase. These results are due to the increase of bond valence of BiNbO4 with the phase transition.