Role of strontium addition on the phase transition of lanthanum copper oxide from K2NiF4 to perovskite structure

Ho Chieh Yu, Kuan Zong Fung

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)

Abstract

Without Sr addition, the sintered La2O3 and CuO powder mixture in a mole ratio of 1:2 formed K2NiF4-structured La2CuO4 with excess CuO. When 15% of strontium was added, La2CuO4 transformed into the single perovskite La1-xSrxCuO2.5-δ phase with orthorhombic structure. As the strontium addition increased to 20%, the perovskite lattice changed from orthorhombic to tetragonal. These phase transitions may be attributed to the enhanced oxidation of the divalent cupper ions (Cu2+) to trivalent ones (Cu3+) by the strontium addition. Based on the electroneutrality in an ABO3 perovskite lattice, a divalent cation is unstable in the B-site cation sub-lattice when the A-site is occupied by a trivalent cation such as La3+. As strontium was added into the A-site cation sub-lattice, the oxidation of Cu2+ ion into trivalent Cu3+ ion was enhanced. The increase of Cu3+ concentration strengthened the electrostatic bonding (ESB) of copper ions with their neighboring anions. Consequently, the symmetrical tetragonal Sr-doped lanthanum copper oxide was obtained.

Original languageEnglish
Pages (from-to)62-68
Number of pages7
JournalJournal of Alloys and Compounds
Volume440
Issue number1-2
DOIs
Publication statusPublished - 2007 Aug 16

All Science Journal Classification (ASJC) codes

  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry

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