Dielectric investigation of MIIMIV(PO4)2 double orthophosphates (MII = Ca, Sr, Ba, Pb; MIV = Ti, Zr, Hf, Ge, Sn)

MIIMIV(PO4)2 (MII = Ca, Sr, Ba, Pb; MIV = Ti, Zr, Hf, Ge, Sn) ceramics were prepared by solid state reaction method and consolidated by spark plasma sintering in order to study their electrical properties. The dielectric study performed at room temperature was aimed to determine the basic electrical properties of these compounds. Maxwell–Wagner polarization contributions, which are active at low frequencies cause a strong extrinsic increase of both real and imaginary part of permittivity as well of the dc-conductivity for BaZr(PO4)2, BaTi(PO4)2, BaHf(PO4)2, and SrGe(PO4)2 double orthophosphates. Moderate real (ε′r=20–150)(ε′r=20–150) and imaginary low-frequency permittivity (ε′r=7–300)(ε′r=7–300) and typical Debye relaxation with relaxation time in the range of ms is typical for: PbHf(PO4)2, PbZn(PO4)2, and CaGe(PO4)2. At high-frequency (f = 109 Hz), the ceramics have permittivities of 2.29÷8.02 and tangent loss of 0.003÷0.153. The compounds SrGe(PO4)2, BaGe(PO4)2, BaZr(PO4)2 and BaSn(PO4)2 have excellent high-frequency dielectric characteristics, with losses of 3÷6% and permittivity slightly above 2 and are possible candidate as microwave ceramics.

► A series of MIIMIV(PO4)2 (MII = Ca, Sr, Ba, Pb; MIV = Ti, Zr, Hf, Ge, Sn) dense ceramics were prepared by solid state reaction and consolidated by spark plasma sintering. ► The dielectric study performed at room temperature was aimed to determine the basic electrical properties of these compounds, which were never reported. ► Moderate real (ε′r=20–150)(ε′r=20–150) and imaginary low-frequency permittivity (ε′r=7–300)(ε′r=7–300) and typical Debye relaxation with relaxation time in the range of ms is typical for: PbHf(PO4)2, PbZn(PO4)2, and CaGe(PO4)2. ► Maxwell–Wagner polarization contributions, which are active at low frequencies cause a strong extrinsic increase of both real and imaginary part of permittivity as well of the dc-conductivity for BaZr(PO4)2 (ionic conductor character), BaTi(PO4)2, BaHf(PO4)2 and SrGe(PO4)2 double orthophosphates. ► At high frequency (f = 109 Hz), the ceramics have permittivities of 2.29÷8.02 and tangent loss of 0.003÷0.153. The compounds SrGe(PO4)2, BaGe(PO4)2, BaZr(PO4)2 and BaSn(PO4)2 have excellent high-frequency dielectric characteristics, with losses of 3÷6% and permittivity slightly above 2 and are possible candidate as microwave ceramics.