On the Feasibility of Growing Pb[(Zn1/3Nb2/3)0.91Ti0.09]O3 Single Crystals

• Published in: Advanced functional materials 2004-02, Vol.14 (2), p.169-173
• Main Authors: Fang, B.-J., Shan, Y.-J., Xu, H.-Q., Luo, H.-S., Yin, Z.-W.
• Format: Article
• Language: English
• Subjects: Bridgman method; Lead zinc niobate titanates; Perovskites; Piezoelectrics
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.200304491

Pb[(Zn1/3Nb2/3)0.91Ti0.09]O3 (PZNT91/9) single crystals were grown by two methods: from solution using PbO as a self‐fluxing agent (SC method) and directly from the melt without fluxing (MC method). In both growth methods, an allomeric Pb[(Mg1/3‐Nb2/3)0.69Ti0.31]O3 (PMNT69/31) single crystal was used as a seed. X‐ray diffraction patterns of ground crystals showed that phase‐pure perovskite PZNT91/9 single crystals were successfully fabricated by the above two methods. The composition of the crystals obtained by both the SC and MC methods was analyzed using X‐ray fluorescence, which confirmed that the crystal composition is close to the nominal value, although volatilization of PbO and segregation during crystal growth are inevitable. The MC PZNT91/9 crystals exhibit excellent piezoelectric properties, with the piezoelectric constant, d33, in the range of 1800–2200 pC N–1. This value is comparable to that of the SC crystals. However, the MC crystals show an abnormal dielectric behavior. In contrast with the SC crystals, in the MC crystals a much broader dielectric peak appears in the dielectric response curves, accompanied by a much lower peak temperature of around 105 °C. Furthermore, frequency dispersion is apparent over a much wider temperature range (even more apparent than in pure relaxors), where a large, i.e., about 70 °C, full width at half maximum (FWHM) for the dielectric peaks is observed in the dielectric response. It is speculated that such an unusual phenomenon correlates with defects, microinhomogeneities, and polar regions in the as‐grown MC crystals. The origins of this abnormality have not been interpreted in detail until now. However, optical observation of the domain structure confirms that both the SC and MC crystals possess complex structural states. Pb[(Zn1/3Nb2/3)0.91Ti0.09]O3 (PZNT91/9) single crystals were grown successfully direct from the melt (MC method) for the first time. Although PZNT91/9 crystals grown by the MC method and from solution using PbO as a self‐fluxing agent (SC method) are of pure perovskite phase, their dielectric performances exhibit astonishing differences. The MC PZNT91/9 crystal also exhibits excellent piezoelectric properties, with a piezoelectric constant d33 in the range of ∼ 1800–2200 pC N–1, which is comparable to that of the SC crystal.