New methods for the preparation and dielectric properties of Lа2 − xSrxNiO4 (х = 1/8) ceramic

• A new fuel in solution combustion synthesis of fine powder La15/8Sr1/8NiO4.
• Changes in the morphology of the ceramic La15/8Sr1/8NiO4 after thermobaric treatment.
• Changes in structural parameters of the La15/8Sr1/8NiO4 after thermobaric treatment.
• Increase of the dielectric constant of the thermobaric treated ceramic La15/8Sr1/8NiO4.
• Using of dielectric modulus and impedance formalisms, of equivalent circuits method.

The perovskite-type oxide La2−xSrxNiO4 (x = 1/8) was prepared by a new precursor route. The reaction proceeds in the self-ignition mode. Single-phase powder and gas-tight ceramic samples can be produced by single annealing of decomposition products. It was shown that as a result of thermobaric treatment of La2−xSrxNiO4 (x = 1/8) the solid solution La2−xSrxNiO4 with a higher concentration of strontium and the second phase La3Ni2O7 are formed. Short-term (5 min) thermobaric treatment (P = 2.5 GPa) at t° = 900 °С changes the unit cell parameters, but is not accompanied by structural transitions. At the same time, morphological restructuring of the sample occurs—the agglomerates delaminate into thin plates crystals. It was established that the permittivity of the material exposed to thermobaric treatment is much higher compared to that of the sample annealed at atmospheric pressure and virtually does not depend on frequency in a wide temperature range.

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