Microwave absorption properties of dielectric La1.5Sr0.5NiO4 ultrafine particles

La2-xSrxNiO4 compounds are well known dielectric materials that have colossal permittivities (epsilon(R) > 10(7)). In the present work, the powder of La1.5Sr0.5NiO4 ultrafine particles was prepared by a combinatorial method of solid-state reaction and high-energy ball milling. Magnetic measurements, M(H), show a very small magnetization and paramagnetic characteristics at room temperature. Flat layers of,La2-xSrxNiO4/paraffin mixture of different thicknesses (t) exhibits strong microwave absorption resonances in the 4-18 GHz range. The reflection loss (RL) decreases with t and reaches down to 36.7 dB for t= 3.0 mm. The impedance matching (vertical bar Z vertical bar= Z(0) = 377 Omega), rather than the phase matching mechanism, is found responsible for the resonance for 1.5 mm <= t <= 3.0 mm. Further increase in the thickness leads to vertical bar Z vertical bar > Z(0) at all frequencies and a reduced absorption. The influence of non-metal backing is also discussed. The obtained low RL suggests that La1.5Sr0.5NiO4 particles could be a potential filler for high performance radar absorbing material. (C) 2014 Elsevier B.V. All rights reserved.