Crystal Growth of Pyrochlore Pr2zr2o7 and its La and Nd Analogs Using Flux Method

Abstract

We report the growth of millimeter-sized single crystals of Pr2Zr2$O7 using PbO-PbF2 flux in the temperature range 1250°C to 1350°C, significantly below the order-disorder transition (~2000°C). The applicability of this flux for the growth of pyrochlores Nd2Zr2O7 and La2Zr2O7 is also demonstrated. The grown crystals exhibit well-formed octahedral shape and high structural quality as confirmed by high-resolution TEM, FESEM, Raman, and magnetic susceptibility measurements. Analysis of the lattice constants and magnetic susceptibilities of the grown crystals reveals that even the best-grown crystals exhibit slight antistuffing ~(2–3 at.%); i.e., with Pr/Zr ratios < 1. Sintered samples with varying levels of stuffing and antistuffing (Pr/Zr ≡ 2+x/2-x; -0.1 ≤ x ≤ 0.1) were used to establish a correlation between lattice constants of the grown crystals and their Pr : Zr composition. Our study establishes the suitability of PbO-PbF2 flux for growing high-quality pyrochlore zirconates, offering an alternative to the high temperature (>2500°C) xenon-lamp-based floating-zone method previously employed for these materials.

Keywords: Pyrochlore, Flux method, Spin ice, Pr2Zr2O7, (Anti-)Stuffuing