Effect of Yttrium (20%) doping on mechanical properties of rare earth nano lanthanum phosphate (LaPO4) synthesized by aqueous sol-gel process

Abstract

In this study, Nascent Lanthanum Phosphate (LaPO4) and LaPO4 with 20% reinforced Yttria (Y2O3) precursor ceramic powder was synthesized through aqueous Sol-gel route, where theLaPO4 and LaPO4/Y2O3 powder was sourced from Lanthanum chloride (LaCl3) and orthophosphoric acid (H3PO4). By sintering the precursor powder at 1400 °C for 2 h, a relatively high-density composite material of LaPO4 (97.4%) and LaPO4/Y2O3 (98.4%) were fabricated. Through X-ray powder diffraction (XRD) experiment, the results revealed that LaPO4 and LaPO4/Y2O3 electrolyte samples sintered at 1400 °C for 2 h is impurity free and thereby elemental composition of the powders is also verified. Further, a small quantity of LaP2 and La2O3elements formed during the synthesis of LaPO4 was found to contribute more on corrosion resistance and high withstanding capacity of the material. 26% of YPO4 formed due to a chemical reaction between Yttrium and Lanthanum made this composite a suitable candidate material for high-temperature applications. Various mechanical characterization tests such as micro-hardness, flexural strength, and compression capacity were studied, where the microscopic analysis provided comprehensive information about both transgranular and intergranular types of failure on the fractured regions of LaPO4 and LaPO4/Y2O3 material. The MicroVicker'shardness of LaPO4 and composite was found to be 5 GPa and 5.2 GPa, respectively. When compared with the nascent sample, on an average, 22% reduction in flexural strength and a 1.05% increase in Young's modulus are observed for the high-density composite.