The states of copper impurities in PLZT 8/65/35 relaxor: An ESR study

Abstract

ESR investigation of PLZT 8/65/35 relaxor ferroelectric doped by 0.01; 0.1; and 1% of copper oxide was performed at 4.2 K ≤ T ≤ 300 K in 3 cm and 1.5 cm regions both before and after the samples annealing in oxygen and hydrogen atmospheres. The observed spectra were shown to be the superpositions of those Cu²⁺ in axial and cubic symmetry field. The axial symmetry spectrum is stipulated by Cu²⁺ substituted for Ti⁴⁺ with its excess charge compensation by La³⁺ in its nearest neighbour, meanwhile cubic symmetry centers are those with the compensation in distant spheres. The sample annealing in oxygen atmosphere did not change spectra. meanwhile cubic centers completely disappeared on reduced samples and the concentration axial one decreased. The narrow line which appeared in the reduced samples near g_eff = 2.001 was shown to be that the electron trapped by oxygen vacancy (F -center model). The existance of electric dipoles Cu³⁺ −La³⁺ and the dipoles Me³⁺ −La³⁺ (Me = Fe, Cr, Mn) in doped by Me ions samples is discussed as the main reason of essential T, increasing in doped PLZT.

Key Words:

• Ferroelectrics
• relaxors
• impurities
• PLZT