Lanthanum hydroxycarbonate (LaOHCO3) spheres were synthesized with an experimental investigation on the role of capping agent by using homogeneous precipitation method. The prepared LaOHCO3 was analyzed using XRD, FT-IR, SEM, TGA and photoluminescence (PL) to understand its formation. From the XRD spectrum, variation in the crystallite size, strain distributions, dislocation density and the number of unit cells in the crystal were obtained by using Debye Scherer's relation, Williamson-hall and Stoke Wilson formula. From the results, various intermediate products and morphology were observed before the formation of LaOHCO3 sphere if citric acid (CA) was used as a capping agent. In contrast, there is no intermediate product formation in the absence of CA. By using fluorescence spectrophotometry, the PL spectrum of LaOHCO3 and the relation between crystalline size and emission intensity of the PL spectrum was studied in the presence and absence of CA with time. For both the cases, the emission was observed at the wavelengths of 420, 438 and 465 nm at excitation wavelength of 365 nm but the only variation in the emission intensity was observed due to change in the morphology and crystalline size of LaOHCO3. In the absence of CA, the relation between emission intensity and crystalline size was directly proportional to each other with time. In contrast, the relationship of the prepared LaOHCO3 with CA was contrary due to the variation in the morphology and crystalline size. © 2020 The Society of Powder Technology Japan