Determination of impurities in lead zirconate–titanate electroceramics by inductively coupled plasma atomic emission spectrometry

Abstract

An analytical method was developed for the determination of Al, Ba, Ca, Hf, Mg, Si and Sr impurities and Co, Cr, Cu, Fe, Mn, Nb, Ni, P, W and Zn dopants in lead zirconate–titanate (PZT) electroceramics by inductively coupled plasma atomic emission spectrometry. A niobium-doped dense PZT ceramic sample was used. Sample dissolution was achieved by using: decomposition with HF + H₂SO₄ in a poly(tetrafluoroethylene)-lined pressure vessel at 170 °C for 16 h followed by evaporation to dryness and dissolution of the residue with HCl; decomposition with (NH₄)₂SO₄+H₂SO₄ in a glass beaker followed by evaporation to dryness and dissolution of the residue with HCl; and fusion with Li₂B₄O₇ in a graphite crucible and dissolution of the melt with 1+24 v/v HNO₃. For each element, an analytical line free from spectral interference was selected. The decomposition reagents present in the final solutions of the sample (HCl and Li₂B₄O₇–HNO₃), and the Ti and Zr macro-constituents, decrease the emission signals substantially. Nevertheless, the inter-element effect of Pb is negligible. The correction of these matrix effects was carried out by preparing standard solutions, for obtaining detection limits, and calibration by matrix matching. The 3σ detection limits of the impurities were determined using the three decomposition methods and correction of the matrix effects. The lowest values of the detection limits were obtained using acid decompositions, and were between ≈0.1 µg g^–1 for CaO, MgO and SrO, and 461 µg g^–1 for P₂O₅. The analytical results obtained for 17 minor and trace elements using the three decomposition methods were in excellent agreement. Good precision and accuracy were attained; the relative standard deviations for the results obtained for each element for each dissolution method ranged in general from 3 to 7%.