Journal of Crystal Growth 234 (2002) 545–550 Effect of rare-earth dopants on the growth and properties of triglycine sulphate single crystals R. Muralidharan, R. Mohankumar, P.M. Ushasree, R. Jayavel, P. Ramasamy* Crystal Growth Centre, Anna University, Chennai 600 025, India Received 20 August 2001; accepted 5 September 2001 Communicated by M. Schieber Abstract The effect of rare-earth ion dopants La, Ce and Nd on the growth aspects and ferroelectric properties of triglycine sulphate single crystals is reported. The incorporation of dopants into the grown crystals is far below the concentration in the mother solution. The dopants significantly modify the morphology of the crystals. Dielectric measurements revealed that the dielectric constant of Ce doped triglycine sulphate (TGS) increases rapidly at the transition temperature. Well-saturated rectangular hysteresis loops have been observed for all the doped crystals. Lenticular ferroelectric domain patterns were observed on the [0 1 0] plane of the grown crystals. Among the three dopants, La doped TGS possess a high Curie temperature and coercive field values. r 2002 Elsevier Science B.V. All rights reserved. Keywords: A1. Crystal morphology; A2. Growth from solutions; B2. Ferroelectric materials 1. Introduction Crystals of triglycine sulphate (TGS), a well- known ferroelectric material, find wide application as room temperature IR detectors [1]. TGS is one of the very few ferroelectrics known to exhibit a second-order phase transition and hence offers possibilities for the observation of genuine critical phenomenon very close to the Curie temperature. TGS is an order–disorder-type ferroelectrics with a transition from ferroelectric to paraelectric phase at 491C, having high pyroelectric coefficient and low dielectric constant values [2]. Despite its promising features, such as room temperature operation and operation without external bias voltage, TGS crystals have a tendency to polariza- tion reversal. In order to overcome this difficulty, there have been several studies with different dopants to achieve effective internal bias and desired ferroelectric properties of TGS crystals. Even though many studies have been performed with different amino acid doping [3–5] and metal ion doping [6–8], there are only very few reports on rare-earth doped TGS crystals [9,10]. Doping of heavy rare-earth ions like Ho, Tm and Yb creates structural and chemical defects in the crystal and also the defect density depends on the electronic configuration of the rare-earth ions [9]. In the case of light rare-earth ion doping, the crystal structure remains unaltered [10]. However, *Corresponding author. Tel./fax: +91-44-2352774. E-mail addresses: pramasamy@annauniv.edu, proframasa- my@hotmail.com (P. Ramasamy). 0022-0248/02/$ - see front matter r 2002 Elsevier Science B.V. All rights reserved. PII:S0022-0248(01)01723-7