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TSANI BAGUS ERYANA

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Abstrak (Bhs. Indonesia)

Material La₀,₆₇Ba₀,₃₃MnO₃ (LBMO) berstruktur perovskit berpotensi digunakan sebagai penyerap gelombang mikro karena memiliki kombinasi rugi dielektrik dan rugi magnetik yang mendukung mekanisme absorpsi gelombang elektromagnetik. Penelitian ini bertujuan menganalisis pengaruh variasi suhu sintering (700 °C, 800 °C, dan 900 °C) terhadap struktur kristal, morfologi, dan kemampuan penyerapan gelombang mikro material LBMO yang disintesis menggunakan metode Pechini. Karakterisasi dilakukan menggunakan X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM), dan Vector Network Analyzer (VNA) pada rentang frekuensi 8–12 GHz. Hasil XRD menunjukkan bahwa material terdiri atas fasa utama LBMO berstruktur ortorombik (space group Imma) dan fasa sekunder Mn₃O₄, dengan ukuran kristalit yang meningkat seiring kenaikan suhu sintering (33,88 nm; 42,48 nm; 47,25 nm), disertai peningkatan fraksi fasa Mn₃O₄ (5,19%; 15,08%; 23,56%) dan penurunan fraksi fasa utama LBMO. Hasil TEM mengonfirmasi peningkatan ukuran partikel rata-rata (84,408 nm; 89,006 nm; 92,571 nm) akibat mekanisme grain growth. Pengujian VNA menunjukkan bahwa sampel yang disinter pada 700 °C memiliki performa absorpsi terbaik dengan nilai reflection loss (R_L) minimum sebesar −12,49 dB pada frekuensi 11,64 GHz dan daya serap sebesar 94,36%, jauh lebih tinggi dibandingkan sampel 800 °C (73,78%) dan 900 °C (71,71%). Penurunan performa absorpsi pada suhu sintering yang lebih tinggi dijelaskan melalui degradasi struktur core–shell akibat pertumbuhan partikel dan meningkatnya fasa sekunder Mn₃O₄, yang mengurangi kesesuaian impedansi (impedance matching) material terhadap ruang bebas. Berdasarkan hasil tersebut, suhu sintering 700 °C direkomendasikan sebagai kondisi optimum untuk menghasilkan material La₀,₆₇Ba₀,₃₃MnO₃ dengan performa penyerap gelombang mikro terbaik.

Abtrak (Bhs. Inggris)

La₀.₆₇Ba₀.₃₃MnO₃ (LBMO) with a perovskite structure has potential application as a microwave absorber due to its combination of dielectric loss and magnetic loss that supports electromagnetic wave absorption mechanisms. This study aims to analyze the effect of sintering temperature variations (700 °C, 800 °C, and 900 °C) on the crystal structure, morphology, and microwave absorption performance of LBMO synthesized via the Pechini method. Characterization was conducted using X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM), and a Vector Network Analyzer (VNA) in the 8–12 GHz frequency range. XRD results revealed that the material consists of a primary orthorhombic LBMO phase (Imma space group) and a secondary Mn₃O₄ phase. The crystallite size increased with higher sintering temperatures (33.88 nm, 42.48 nm, and 47.25 nm), accompanied by an increase in the Mn₃O₄ phase fraction (5.19%, 15.08%, and 23.56%) and a decrease in the primary LBMO phase fraction. TEM analysis confirmed an increase in average particle size (84.408 nm, 89.006 nm, and 92.571 nm) driven by the grain growth mechanism. VNA testing demonstrated that the sample sintered at 700 °C exhibited the best absorption performance, achieving a minimum reflection loss (R_L) of −12.49 dB at a frequency of 11.64 GHz and an absorption efficiency of 94.36%, significantly higher than the 800 °C (73.78%) and 900 °C (71.71%) samples. The decline in absorption performance at higher sintering temperatures is attributed to the degradation of the core–shell structure caused by particle growth and the increase in the secondary Mn₃O₄ phase, which reduced the material's impedance matching with free space. Based on these findings, a sintering temperature of 700 °C is recommended as the optimum condition for producing La₀.₆₇Ba₀.₃₃MnO₃ with optimal microwave-absorbing capabilities.

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