X-ray and thermal studies of ferroelectric Dy2(MoO4)3

Abstract

Dysprosium molybdate, Dy2(MoO4)3, displays a ferroelectric phase transition at 145 ~ The X-ray and thermal (DTA, TG and DSC) properties of this compound have been studied. The X-ray study confirmed the ferroelectric phase in the orthorhombic space group Pba2. Thermal analysis demonstrated the existence of a ferroelectnc and another phase transmon in this compound.Dysprosium molybdate, Dy2(MoO4)3, is a member of the family of rare earth molybdates with general formula R2(MoO4) 3 (where R = trivalent rare earth ion). These materials have been found to be promising for many industrial applications, due to some of their special physical properties, such as ferroelectric-ferroelastic, etc. [1][2][3]. Ferroelectric properties have been reported for the orthorhombic modification of gadolinium molybdate [4]. The ferroelectric, ferroelastic and other related properties for some of the compounds of this family have made them attractive for device applicatiqns [5,6]. Dy2(MoO4)3 (hereafter DMO) is isostructural with gadolinium molybdate, GMO, and of interest by virtue of its ferroelectric properties [1]. Only two rare earth molybdates, GMO and TMO (terbium molybdate Tb2(MoO4)3) , have been thoroughly investigated [7], because of their relatively easy growth of good-quality single-crystals by the Czochralsky method [8]. However, little effort has been made to study the other isostructural molybdates, in part because of the specific difficulties involved in obtaining their single-crystals as a result of their complex morphology [9, 10]. The complex morphology is particularly a problem in the case of DMO, because of its reconstructive phase transition at about 1030 ~ , accompanied by disintegration of the crystal itself [11]. It has been observed that its structural modification and physical properties are highly sensitive to the conditions of preparation. The ferroelectric fl' phase in the compound can be obtained only by rapidly quenching the sample from the high-temperature (1000 ~ fl phase to room temperature. As not much work has been done on DMO, we have studied its X-ray and thermalJohn Wiley & Sons, Limited, Chichester Akad~miai Kiad6, Budapest

The crystal structure and thermal expansion properties of solid solutions Ln2−xDyxW3O12 (Ln=Er and Y)

“…3a and b, respectively. Their TG curves keep almost unchanged with increasing temperature and DTA curves show endothermic peaks, results of the phase transitions mentioned above [19]. The weigh losses of these compounds are negligible which reveals their good thermal stability in the testing temperature range.…”

“…It was reported that compound Dy 2 W 3 O 12 experience a phase transition at 1030 • C [19]. Compounds Er 2−x Dy x W 3 O 12 (1.2 ≤ x ≤ 2.0) all take the Dy 2 W 3 O 12 -type structure and have the similar phase transition.…”

A tetragonal form of dysprosium orthomolybdate at room temperature

“…Displacement ellipsoids are drawn at the 70% probability level. Roy et al, 1989). Above 1303 K, a reconstructive phase transition into a cubic form of Dy 2 (MoO 4 ) 3 was reported (Roy et al, 1989;Brixner, 1973).…”

“…Roy et al, 1989). Above 1303 K, a reconstructive phase transition into a cubic form of Dy 2 (MoO 4 ) 3 was reported (Roy et al, 1989;Brixner, 1973). In this work, single crystals of Dy 2 (MoO 4 ) 3 have been obtained with the high-temperature -form tetragonal crystal structure, and the structure refinement based on roomtemperature single-crystal X-ray diffraction data has been performed.…”

“…Dysprosium molybdate, Dy 2 (MoO 4 ) 3 , shows a ferroelectric-ferroelastic transition below 418 K (Roy et al, 1989). According to X-ray powder diffraction, the ferroelectric phase crystallizes in orthorhombic symmetry (space group Pba2;…”