Microwave dielectric properties of A2P2O7 (A = Ca, Sr, Ba;: Mg, Zn, Mn)

Microwave dielectric properties of A(2)P(2)O(7) (A = Ca, Sr, Ba, Mn, Mg, Ba) ceramic materials were investigated by a network analyzer at the frequency of 10GHz. It was found that A(2)P(2)O(7) ceramics could be sintered at relatively lower temperature below 1150degreesC, although the thortveitite type series, Mn2P2O7, alpha-Mg2P2O7 and alpha-Zn2P2O7 with smaller ionic radii of A cations were hard to sinter to full density. The dielectric constant of A(2)P(2)O(7) is lower than 10. The Q x f value increased according to the sequence of delta-Ba2P2O7, alpha-Sr2P2O7 and beta-Ca2P2O7 in dichromatic type series, and the sequence of Mn2P2O7, alpha-Mg2P2O7 and alpha-Zn2P2O7 in thortveitite type series, respectively. The temperature coefficient of resonant frequency rf for all samples exhibits negative value. Larger tau(f) for alpha-Zn2P2O7, alpha-Mg2P2O7 and delta-Ba2P2O7 is mainly due to their reversible phase transformations. The microwave dielectric properties were discussed from the point view of bond valence.