Local dopant compositions within individual alpha-Sialon grains were measured by analytical electron microscopy (AEM) in hot-pressed Ca(x)Si(12-3x)Al(3x)O(x)N(16-x) (x = 0.3-1.4) ceramics. The reduction of local x values from the nominal dopant compositions is about 40% in general, and it reaches 60% for the end member (x = 1.4) which contains inclusions of AlN-based 21R phase. This results exhibit stronger departures from x than the previous report of 30% dopants missing in alpha-Sialon phase by electron probe micro-analysis (EPMA) [J Eur Ceram Soc 19: 1637, 1999]. Amorphous films of similar to 1 nm thick were commonly found at grain boundaries (GBs), which could only take a small fraction of undetected dopants while the film composition exhibits a quite different behavior. The general presence of GB films can rationalize the discrepancy between AEM and EPMA results by their differences in probe size and detection geometry, while the much larger gap in the end member suggests the existence of Ca-rich glasses in the intergranular regions. By excluding this end member, a linear relation between dopant solution and lattice expansion is restored in alpha-Sialon structure, which leads to 20 and 80% increases of the expansion coefficients from those given in the previous and original reports, respectively. This study not only demonstrated the necessity of solubility study in ceramics by AEM refinement, but also opens a new front to correlate the solution behavior with the intergranular glass/amorphous structures, both were regarded so far as largely independent.