Solid-state 93Nb MAS NMR studies of single crystal Pb(Mg1/3Nb2/3)O3, (PMN) and Pb(Zn1/3Nb2/3)O3, (PZN) and related lead titanate solid-solution relaxor ferroelectrics

Solid-state 93Nb MAS NMR spectra measured at 14.1 Tesla of single crystal Pb(Mg1/3Nb2/3 (PMN), Pb(Zn1/3Nb2/3)O3 (PZN), 0.93 PMN/0.07 PT, and 0.92 PZN/0.08 PT, and polycrystalline PMN and 0.90 PMN/0.10 PT materials have two major resonances due to the central transition (+l/2↔-l/2), a sharp peak at ≈-900 ppm, and a broad resonance centered near -980 ppm. The sharp 93Nb signal has a small CQ (≤1 MHz) consistent with high symmetry Nb(V) ion B-sites as a consequence of local Mg/Nb (and Zn/Nb) ordering, and is tentatively assigned to near-cubic Nb(V) B-sites of Nb(OMg)6 (and Nb(OZn)6) configurations. The broad Nb signal near -980 ppm consists of two or more overlapping powder patterns with large CQ values, and are tentatively assigned to lower symmetry Nb(ONb)6-x(OMg)x and Nb(ONb)6-x(OZn)x configurations (where x=0 to 5).The 93Nb NMR spectra of single crystal 0.93 PMN/0.07 PT, 0.65 PMN/0.35 PT, and 0.92 PZN/0.08 PT, and polycrystalline 0.90 PMN/0.10 PT and 0.66 PMN/0.34 PT compared to PMN and PZN are correlated with increases in the mole% PT due to Ti(IV) ion substitution into the B-sites, causing increased B-site disorder. In addition, the 93Nb NMR spectra for both polycrystalline and single crystal PMN and PMN/PTs arc nearly identical, supporting the existence of similar short-range Mg/Nb ordering in these different crystalline forms.

Keywords:

• Solid-state ⁹³Nb NMR
• ferroelectrics
• PMN
• PZN
• order/disorder in perovskites