ORIGINAL PAPER Aqueous sol–gel synthesis of lanthanum phosphate nano rods starting from lanthanum chloride precursor Sasidharan Sankar • Krishna Gopakumar Warrier Received: 7 September 2010 / Accepted: 2 December 2010 / Published online: 14 December 2010 Ó Springer Science+Business Media, LLC 2010 Abstract Aqueous sol–gel technique is reported for synthesizing nanosize, rod shaped lanthanum phosphate particles starting from lanthanum chloride, which is suit- able for variety of applications such as machinable ceramics, thermal barrier coatings and luminescent mate- rials. The phosphate particles are having rod like mor- phology having an overall size in the range 25–100 nm and with an average aspect ratio 4. The morphology is retained even after calcination at 800 °C. The average crystallite size for the as prepared particles was calculated to be 8 nm using Scherrer equation applied on X-ray diffraction (XRD) data. The particles obtained were characterized using photon correlation spectroscopy (PCS), FT-IR spec- troscopy, XRD and Electron Microscopy techniques (TEM and SEM). The phase stability was found using thermo gravimetric analysis. The surface wettability monitored using tensiometer through dynamic contact angle method indicated that lanthanum phosphate surface possesses considerable hydrophobic character. Keywords Lanthanum phosphate Á Nano rods Á Sol–gel Á Lanthanum chloride 1 Introduction Rare earth phosphates are well reported to have applica- tions in various fields such as catalysts [1, 2], thermal barrier coatings [3], machinable ceramics [4], fluorescent coatings [5], biofunctionalization [6], bioimaging [7] and for many other functional applications. Lanthanum phos- phate has high melting point above 1,900 °C[8], low dielectric constant [9], thermal expansion co-efficient similar to that of alumina [10], non reactivity with metals [11] and also many high temperature oxides. Lanthanum phosphate has been found to act as an excellent host/matrix for development of photoluminescent materials. This material which is known for its ability to function as a solid state proton conductor [12] is also widely reported as a good Lewis acid catalyst. Yusaku Takita et al. [13] had studied the use of lanthanum phosphate in oxidative dehydrogenation of iso-butane to iso-butene. Hence rare earth phosphates in general and lanthanum phosphate in particular have been reported as very potential materials. Preparation of rare earth phosphate particulates in fine sizes were achieved through various techniques including precipitation [14, 15], hydrothermal [16], solid–liquid reaction [17], colloidal [18], micro wave [19], ultrasoni- cation [20] and sol–gel [21]. The starting compound in nearly all the above techniques is rare earth nitrate, car- bonate or acetate and lanthanum phosphate nano particles in the range of 50–200 nm could be obtained. Lanthanum nitrate has been used more often as the starting material in the earlier investigations [16]. Earlier Rajesh et al. [25] had reported a sol–gel route for synthesis of rod shaped lan- thanum phosphate nanoparticles prepared from lanthanum nitrate for functional applications. They could obtain lan- thanum phosphate nanoparticles with an average crystallite size of 11 nm. However, for scaling up of the process for lanthanum phosphate particles starting from lanthanum nitrate has certain difficulties, especially with respect to safe disposal of nitrate containing effluents. The accumulation of nitrates in water is already well known to cause environmental S. Sankar Á K. G. Warrier (&) Materials and Minerals Division, National Institute for Interdisciplinary Science and Technology, Council of Scientific & Industrial Research, Thiruvananthapuram 695 019, India e-mail: wwarrierkgk@yahoo.co.in 123 J Sol-Gel Sci Technol (2011) 58:195–200 DOI 10.1007/s10971-010-2377-4