Temperature dependence of the nuclear quadrupole interaction at Zr-Ti sites in in the Zr-rich rhombohedral and cubic phases

Abstract

In this paper, the hyperfine quadrupole interaction at the Zr-Ti site of (PZT) polycrystalline samples is studied for the first time. Powders for x = 0, 0.1, 0.2, 0.4, 0.6, 0.8, 0.9 and 1 were prepared and characterized by XRD. The lattice constants and space groups were obtained as functions of Ti concentration. PAC analyses were done for ferroelectric PZT for x = 0.9 and 0.8 as a function of temperature, and for x = 0.6 at RT. Also antiferroelectric was analysed. Low-concentration nuclei were used as probes. In the ferroelectric and paraelectric phases of PZT compounds two sites were occupied by probes. For each site the quadrupole frequency, asymmetry and relative distribution width parameters were obtained as functions of temperature above and below the Curie temperature. For only one site was detected with a static quadrupole interaction below and a nuclear spin-relaxation process above it. Furthermore, the temperature dependence of the hyperfine parameters, the possible origin of both quadrupole interactions in PZT and the perturbation that characterizes the cubic phases of and compounds are discussed.

TDPAC Studies of Local Defects and Phenomena in Ferroics and Multiferroics

“…Fascinatingly, one of them presented highly distributed frequencies over the whole concentration range of Ti, with a predominant site population. An increase in the quadrupole frequency was also observed when x = 0.2 and x = 0.4 [28]. The potential atomic rearrangement observed here gradually decreased at higher Ti concentrations.…”

“…The temperature dependence of the hyperfine quadrupole interactions of polycrystalline samples of PbZr 0.9 Ti 0.1 O 3 and PbZr 0.8 Ti 0.2 O 3 was investigated in [28]. In the ferroelectric and paraelectric phases, two different local environments were reported for the 181 Hf( 181 Ta) probe.…”

Perturbed angular correlation study of 181Ta-doped PbTi1−xHfxO3 compounds

“…In all cases, one of them is by far the most populated (f> 95%), and the corresponding Vzz values are between the typical values observed for other perovskite-type compounds. The other one is characterized by very high V zz values which are outside the expected range obtained in previous PAC studies done in perovskites that display different cell symmetries and by computational simulations [18][19][20][21][22][23][24][25]. Thus, in what follows we will refer only to the highly populated site, being the other one in principle related with some kind of defect, grain boundaries or surface effects.…”

“…In different studies of perovskite-type compounds, the phase stability and the transition temperatures were analyzed in terms of the hyperfine interaction parameters of probe atoms using Perturbed Angular Correlations spectroscopy (PAC) [18][19][20][21][22][23][24]. The Electric Field Gradient tensor (EFG) is a very sensitive physical quantity that strongly depends on the charge distribution in the close neighbor of the probe.…”

Interacciones hiperfinas en Ba_xSr_1-xHfO₃

“…En el espectr-metro fue colcado un horno que alcanza 1200 o C con una estabilidad de 1 o C. Cada medida PAC fue adquirida durante 2 dias y consiste en la acumulaci-n de coincidencias de los rayos de 133 con 482 keV que forman ‡ngulos de 90¼ y 180¼ (C(90¼,t) y C(180¼,t)). A partir de dichas coincidencias se calcul-el cociente [1] donde A 22 es la anisotrop'a a tiempo cero y G 22 (t) la curva de precesi-n de spin. Para fuente policristalina se tiene G22(t) = Σ σ 2n cos(ω n t) exp(-δω n t), [2] donde los coeficientes σ 2n dependen de η, las frecuencias ω n depende η y ω Q y el coeficiente δ es el ancho de l'nea.…”